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Super Moderator
40,514 Posts
Discussion Starter #1 (Edited)
The first question straight out of the box that many new members of the forum have about their Genesis Coupe is “what mods should I do first?” The answer to this question is not as straight forward as to detail a list of components to purchase and bolt on as the answer is going to vary according to your chosen trim level and engine specification and model year. For the sake of simplicity, I will be focusing primarily on the platform that I own (a 2011 2.0T R Spec); however, much of this write up will also apply to other trim levels. Keep in mind that there is no such thing as a “best mod”; however, depending on your specific goals, there may be an order to what mods you need to think about doing first, middle, and last. It is not my intent with this write up to endorse or recommend one product or vendor over another; however, you will find that many of the DIYs and stickies that I will be sharing may lean towards one product or another. I take no credit for coming up with that knowledge only taking the time to research it for your ease, so if the best write up tends to lean one direction or another, do not take it to mean that I am recommending that is the direction you should go.

"What should be my 1st mod,” “What mod next,” “I have X money, what should I buy”

Before you start spending a lot of money on pieces parts, the first thing you should be doing is determining what it is you want to do with the car. Is it your daily driver? Are you worried that you will “void” your warranty by modifying your car? Do you want to track your car? Are you a weekend enthusiast? Do you want to show your car? These are important questions you really need to answer before you buy anything as many modifications for one activity are not always compatible with other activities.

Don’t be “that” guy. You know, the one who spends a lot of money on the wrong pieces parts only to have to buy the right pieces parts later while taking it in the shorts trying to sell his/her old pieces parts. Modding is an expensive hobby and it will demand a lot of your time and effort (not to mention a great deal of frustration and angst) to get your car to where you want it. Even with a good plan, you may find that when you get to where you thought you wanted to be that it isn’t really what you wanted. Choosing to do something cheap and easy up front just to say that you are doing something is not a path forward to creating the street/track/dyno machine of your dreams. This ain’t no Honda…yo!

The question you should answer yourself before every modification decision is: “how much is this part going to COST, and is it WORTH IT?" This is ultimately your decision, as it's your money, and your opinion. However there are others who may have done the same work you are about to and feel as if it WAS OR WAS NOT worth it and can explain why. Do your research and make an informed decision.

A tuner’s axiom: YOU MAY ONLY PICK TWO: Cheap, Fast, or Reliable.

The absolute BEST way to make sure your money is spent wisely is to not to do the same thing twice.

For the sake of simplicity, I have broken down the mods that can be done into several categories that fit different end states:

HANDLING (suspension, braking, traction, tires and over all handling)
BOLT ON'S (they suck, but are great supporting mods)
LOOKS (it's your car make it look how you want- but be warned on going "too far")
AFRs Explained!
Turbo Basics
Water/Meth Injection - Do I need it?
Understanding Suspension Tuning
Tire and Wheel Fitment
Chassis Braces and you...

As I add more content I may be tacking on to the end of wherever the discussion has left me... so use the shortcuts above to jump directly to the section that you want to read about if you don't want to scroll through the various discussions that happened in the middle.

Generally speaking, power goals on a 2.0T range from a bump of 50 or so HP to over 400 HP. Keep in mind that the higher your goals, the more supporting modifications that will be required to attain those goals and the less driveable your car becomes. The highest documented HP of a 2.0T of 800 whp on a Mustang Dyno on a show car built for SEMA by one of our vendors. While this is not a typical outcome as most people do not have the disposable cash to build a motor to withstand that kind of power, it is a good guideline as to what is possible given enough time and money. Here is a list of some of our members' builds that are more realistic in terms of what you can expect:

Anything you do to your car that changes the performance specs from the OEM spec is going to have other side effects. There is no such thing as a “free” upgrade. More boost does not always equate to more power. Sometimes the only thing more boost will get you is a hole blown into the side of your engine because you did not have the supporting modifications or the tuner did not understand the basic weaknesses of the 2.0L Theta engine and tried to tune your car like an EVO. There are reputable dealers, vendors, and tuners here on this site who can help you meet your performance goals safely. Don’t be this guy:

Here are some great builds others have done:

If I have left your build off this list or if you have a more current build thread going, please don’t take offense. The goal here is to show what could be done depending on different users specific objectives. You can check out the other builds that members are doing on this sub-forum: GenCoupe Build / Projects - Genesis Forum: GenCoupe Hyundai Genesis Forums.

A special note to all of our new 2013+ 2.0T owners:

While this thread is primarily targeted at the 2010-12 group of owners, many of the modifications in this thread also apply to the 2nd generation Genesis Coupe. All of the engine modifications apply, but keep in mind that Hyundai made a lot of improvements with the 2nd generation build to include a different intake manifold, exhaust manifold, turbo, Primary Cat, bypass valve, and intercooler. You can still go for the big turbo builds, but you may have to retrograde some of your parts because there are no 2nd generation upgrade options at this point. All of our tuners have the capability of custom tuning your ECU for turbo upgrades.

Some of the interior modifications involving the center dash will require vendors to make 2nd generation specific pieces parts to make older modifications a viable option. Don't be afraid to read through this thread, but just keep in mind that some of the modifications will not be possible until the aftermarket catches up with you.

And for our 3.8 audience...

You purchased a fine car with power built right in. This is a normally aspirated (NA) car with some limitations. First off, you may notice that around the forum you will hear the 2.0T guys making some big power and you would like to be part of that scene. Unfortunately for you, most of the gains you can get at a reasonable cost is only going to result in double digit (at the most) gains. With a tune, you may be looking at 35-50 additional HP with full bolt-ons. In order to gain more power, it is going to require a substantial outlay of cash to go the forced induction route. From my observation, an unmodified long block can handle up to about 5-8 lbs of boost(turbo or supercharger) and get you in the 350-450 whp power range (tops) depending heavily on the bolt-ons and tune you choose. Beyond that, a full engine rebuild is in order to handle higher boost levels. At that point the sky is the limit with regard to what you can pull out of your V6... but also keep in mind that more power = more bucks. I say this not to discourage our 3.8 community; however, the reality is that it is far easier and far less expensive to get impressive 3 digit power gains from a 2.0T than from a NA 3.8. Be happy that you have a car that does not really need to be modified to get the impressive performance. Out of the box and side by side, a 2.0T isn't a 3.8 in terms of engine performance... so be happy. Don't skip over the performance section of this thread. Although I wrote it targeting the 2.0T folks, much of the theory also applies to you. The more you understand how your car is supposed to work, the better you will understand what components will provide the best gains.

Disclaimer: This is not a "how to" or a "do it yourself" guide. There are plenty of threads out there that describe just about everything you can do on the Genesis Coupe and there is no point in trying to duplicate the efforts of hundreds of subject matter experts on any particular modification. The purpose of this article is to provide a base level of understanding of the Genesis Coupe, its sub components, and aftermarket options available. The modifications suggested by this article are not endorsements of any particular modification or vendor. We do not advocate nor recommend that you make any modification to your car. We provide this information to educate the novice owner as to what components can be reasonably modified to achieve specific goals as established by the car owner. Any and all modifications performed by the owner is done at the discretion of the owner and remains completely, totally, and wholly the responsibility of said owner.

~~~~ And now a word from our Professor on how to properly search a website for stuff ~~~~

Contrary to popular belief, the search bar provided above may not be the best way to search for what you are looking for. Although it uses Google's search engine, the search returns are often not in an order that places what you are looking for at the top of the list. There is hope. Go to Google (or if you have a modern browser and your default search engine is Google... just type your search string in the address bar). Type in your search keywords. Google prioritizes its search in order of importance based on the first word of your search string and for each word following. So, put your most important search keywords first. Or... you can simply type in a question. Google will break the question down and extract the keywords for you. At the end of the search string, type, "" That will limit the search to this site. Enjoy the reward of being able to answer most questions you have on your own.

Note to our more OCD members: There is a very good chance that Google will not return an answer on a silver platter for you. In other words, there may not be anything written about your specific problem because there are so many different permutations of mods, parts, and problems that you can experience. Just because you can't find an answer to your exact problem does not mean that the answers don't apply to you... contrary to popular belief, there are only a few different ways of getting something right so similar parts can have similar issues and similar fixes. Try them first before starting a thread about how your Plasti-Dip won't stick to your wheels.

Last, but certainly not least... to our non-US Coupes located around the world....

There are several references to US law with regard to emissions, safety, and consumer protection regulations and laws in this thread. While these specific laws do not apply to you, there may be similar laws that do apply. Before you mod, know what the laws say you can and can't do to save yourself a lot of headache.

Super Moderator
40,514 Posts
Discussion Starter #2 (Edited)
Engine Performance

What is safe? To begin with, every engine is different. Some stay together quite well at 475 whp power levels while others crap themselves at 300 whp. The general consensus of the community is that 300-350 whp is considered “safe” with stock internals. Your mileage may vary. With good care, and a quality build, cars that have been modified to the “safe” power levels have lasted into the six digit mileage range. The key to a quality build is ensuring you use quality parts and that those parts are properly installed, adjusted, and if need be, tuned. While there are some areas where you can skimp a bit and save money there are other places where saving money is only going to cause more problems down the road than if you had done nothing. Knowing the difference can save you time, money, and a great deal of frustration.

The Tune

The single most significant upgrade that you can do with any stock Genesis Coupe 2.0T or 3.8 that will yield immediate and noticeable benefits with regard to response time, power, and return on investment is a tune. There are a number of vendors on Gencoupe that offer tuning services (this is not a thread to promote any tuner... if you have questions, ask somewhere else) that range from simply narrowing the obscene safety margin that the Hyundai stock tune provides to tuning for bigger turbos and other bolt ons.

When do I "need" a tune?

You need a tune when you upgrade your turbo and/or your fuel injectors. Hyundai's stock tune is adaptive and will allow you to do most bolt-on modifications without having to retune. With that said, you will most likely not notice a significant difference in power after your bolt on modifications if you do not tune your car after having completed said modifications. The real power comes with the tune, not the hardware; however, many tunes will require that you have certain hardware modifications performed.

Will a tune "void" my warranty? (Answer only applies in the United States)

The short answer is no, a tune in of itself cannot "void" your warranty. With that said, you could be setting yourself up for a claim denial on any engine damage that may or may not be the result of the tune if the manufacturer can make a reasonable connection between the tune and the failure. Modifying your car comes with risk. If you cannot afford to foot the repair bill that comes from a failed execution of a modifications, you probably should not modify it.

What can I expect from a tune?

That will depend on the vendor you choose to go with. Every vendor has their "secret sauce" that will allow them to do stuff that other vendors cannot do. Read the various threads on tuning and get a better idea of what each vendor has to offer. Stay away from local tuners who profess to be able to tune a Genesis Coupe. The Genesis Coupe's ECU can only be properly tuned by a handful of tuners in this country and most all of them are represented on this site.

What about self-tuning options?

There are two self tuning options available to the Genesis Coupe 2.0T (sorry 3.8 guys... not so much you). Dynojets CMD and Haltechs Plug and Play ECU. If you are familiar with neither, there is not enough space here to break down what these options can do for you. There are, however, numerous threads on both the CMD and Haltech to answer just about any question that might pop into your little head. Suffice it to say that either option will allow you to blow your car up yourself with very little effort if you do not know what you (or your designated local tuner) is doing. There is no chip or magic pill that you can install that will tune your car for you.​


The point of using a turbo is to produce more power from an engine by forcing more air into it. The more air (and corresponding fuel) that can be introduced, the bigger the bang. To achieve this, a turbo converts energy derived from the escaping exhaust from the engine which it uses to spin a turbine that compresses air from the intake going into the engine via the intake manifold. Taking a little lesson in fluid dynamics from Bernoulli’s Principle which states that there is a corresponding decrease in pressure when flow rates increase, producing pressure at low flow rates (low engine RPMs) requires very little effort from the turbo as long as there is sufficient energy being released from the exhaust to turn the turbine wheel; however, as the flow rate (RPM) increases to the intake manifold and through the engine, the turbo must produce even more pressure to compensate for the increased flow. What this means to you and I is that a turbo has limitations. If it efficient at low RPMs, it tends to be inefficient at high RPMs and vice versa. Increasing the size of the turbo generally means that you lose low end efficiency (boost) so that you can achieve higher efficiency at higher engine RPMs.

The stock turbo on a 2010-12 2.0T is the TD04L-04H-13TK03S. Under stock conditions the turbo is producing approximately 12 PSI boost tapering down to 8 PSI towards redline. While it can adjusted (manually or electronically) to peak at 20 PSI, it can’t hold those levels long and tuning the stock turbo to try to hit a 20 PSI peak only results in spikey performance that is short lived. Adjusting the turbo manually through a boost controller anything more than 1-2 PSI above stock levels can cause a lean condition which can blow a hole in the side of your engine. Messing with your boost pressure with no way to measure what you have done is a recipe for disaster.


The stock intake is arguably pretty efficient as is with the possible exception of the corrugated plastic tubing connecting the filter box to the turbo compressor intake. The general concept is that straighter, shorter, smoother is better. The stock intake box has the advantage of being able to pull air from the ram scoop at the front of the hood above the radiator which essentially creates a cold air intake system. Where things start going a bit wrong with the stock system is that the inside of the plastic intake tubing between the filter and the turbo is not as smooth as it could be and introduces turbulence as the air passes through it. A quality aftermarket short ram intake (SRI) or cold air intake (CAI) with a high flow filter will often be an improvement on the stock intake; however, care must be taken to ensure that the high flow filter is serviced regularly as it tends to pick up contaminants more quickly than the stock system.


There is an ongoing debate between the advantages of SRI vs. a CAI. The SRI is generally the straightest and shortest path from filter to turbo; whereas most designs lose the efficiency of the ram air intake. The CAI pulls air in the dead space behind the front bumper. The air has a bit more distance to travel vs. the SRI, but the air is generally cooler when it arrives at the turbo. I would argue that the temperature differences between the SRI filtered air and the CAI filtered air are not relevant as the only temperature that is relevant is the temperature of the air at the intake manifold as it is mixed with fuel and is introduced into the cylinder right after it has been cooled by the intercooler. An efficient intercooler can eliminate the difference in temperatures between a SRI and a CAI; however, it should be noted that it has never been documented where an engine has hydrolocked using an SRI and higher end SRIs use an air dam to block off some of the engine heat and many use a duct from the ram air intake to infuse fresh air. A CAI sits low enough in the front bumper (especially if the car is lowered) that there is a possibility that it can be submerged in water (i.e. a deep puddle). Once that happens, the turbo will suck the water up through the filter and force it into the engine. Once a cylinder fills with water, the compression stroke jams or “locks” the engine (because water does not compress) and the engine cannot spin. This often results in bent piston rods, broken camshafts, and a host of other problems that generally means replacing the engine.

Why a BOV?

To dispel any myths all modern turbo systems have some kind of pressure relief valve that allows the charge pipe to depressurize when the throttle body plate closes to prevent the pressure in the charge pipe from pushing against the fins of the compressor causing it to stall. The stock system uses a bypass valve (BPV) that routes the pressure back into the intake side of the compressor. Generally speaking, this will be one of the first components that fails when the turbo is tuned to pressurize the charge pipe to a higher pressure than stock levels causing a boost leak. Aftermarket blow off valves (BOVs) are designed to work at higher boost pressures; however, they do not all work the same way. Most BOVs can be set to either vent to atmosphere or recirculate the waste charge air. From a performance standpoint, there is no advantage to either venting method. Also, there is no performance gains or advantage to a hotside or a coldside (hotside-pre intercooler; coldside-post intercooler) installation; however, your decision as to whether to do a hot or cold side installation may be influenced by whether or not you want to recirculate the waste pressure. When installing an aftermarket BOV, be sure to purchase a block off plate that will mount in the location of the stock BPV if you are not installing the BOV in the stock location.

Intercooler piping

The stock intercooler piping tends to flex when under pressure and generally only works with the stock intercooler. The theory behind improving the airflow from turbo to intercooler to intake manifold is the same as what was discussed under the intake. Shorter, straighter, and smoother. You want piping that minimizes the distance the air has to travel, ensure that the airflow path is as straight as you can get it (minimal bends), and eliminate as many possible areas where the flow can be interrupted. What this generally means is that you want piping that is mandrel bent, with as few joints as possible. eBay do it yourself “universal” intercooler piping does not fit this description. Reducing the number of joints eliminates potential boost leak points, pressure expansion points, and potential flow restrictions. Metal is better than reinforced silicone tubing.


As air is drawn into the turbo compressor and being compressed, the temperature of that air is increased dramatically. What we know from high school science class is that as we increase the temperature of a gas, the space between molecules increase. Applying this to your boost system means that your turbo, while increasing pressure, is also the source of a decrease in volumetric efficiency. To counter this effect, the charged air from the turbo is routed through an intercooler that cools the charged air before it gets to the intake manifold. There is a pressure loss associated with the intercooler depending on the size of the intercooler and the number of obstructions within it. Design is of the utmost importance with regard to intercooler efficiency. A good intercooler must not be so big that it takes much of the air coming from the turbo to fill it; must have sufficient fin density to thoroughly scrub the air that is passing through it to allow the heat to be absorbed and released to atmosphere without causing a backflow of pressure back to the turbo, and be made of materials that are efficient at absorbing and transmitting heat. The stock intercooler is generally considered acceptable to about 200 whp. Above these levels, the stock intercooler tends to heat soak and lose considerable efficiency.

Intake manifold

For the most part, the stock intake manifold is pretty well designed. While this does not mean that Hyundai’s design is without flaws or could not be improved upon, aftermarket solutions to improve the stock intake manifold only provide minimal gains (8-10 HP). One of the more significant flaws of the OEM intake manifold design is the fact that airflow to all four cylinders is not balanced. This imbalance can cause an issue with the #1 and #4 cylinders. The #1 cylinder runs stupid rich and the #4 runs leaner than #2 and #3 at higher pressure levels. Porting and polishing the OEM intake manifold can result in some improvement in the distribution of air to the cylinders. In most cases, doing nothing with the stock intake manifold neither hinders or aids your performance.

Intake manifold phenolic spacers

The engine gets hot. How hot does it get? It gets HOT! Anything that is connected to the engine likewise gets hot via contact transference. If the goal of cooling the intake air is to ensure that the coolest air gets into each cylinder, does it make sense to bolt the intake manifold to a heat generator? A phenolic spacer between the engine block and the intake manifold can reduce the amount of heat transfer and keep that intake air cooler caused by contact transference.


While this may seem an odd section to add the topic on gauges, it is also the most appropriate section for all you turbo guys. Before you guys go out there and spend a lot of money on tunes and pieces parts, you should give some consideration to the fact that you have no way of knowing what all these engine modifications are doing to your engine. Every modification to your engine will impact your Air/Fuel ratio. While a tuner will often tune your car with enough safety margin to account for changes in atmospheric temperature, pressure, and humidity, the tuner cannot account for the effectiveness of your aftermarket modifications, the octane level of the fuel you are putting into your tank, or acts of god or stupidity that may strike your car at any moment. The 2010-12 Genesis Coupe (you '13+ guys are safe) does not have a way to measure the wideband oxygen levels of the exhaust or provide you with an idea of what boost level you are running. With that said, the investment in a high quality set of Boost and Wideband O2 gauges will be your single most important modification. For you '13+ turbo guys, you will find that the Cracker Jack prize gauges are really difficult to read precisely and you may also want to upgrade your gauges with ones that are easier to read. The most advanced gauges have data logging capabilities that will allow you to essentially replay something that you may have missed.

If you spend your money on nothing else... make sure you know where your Boost Level and O2 levels are

Super Moderator
40,514 Posts
Discussion Starter #3 (Edited)
Engine Performance (continued)

Fuel Injectors (10-12 2.0T Coupes)

Now that we have thoroughly kicked the airflow horse, let us move to the other side of the equation and discuss the fuel. The question of whether to upgrade your injectors comes up at least once a week on this forum. Again, as with the other topics under this performance section, it depends on what your power goals are. Upgraded injectors are not required if you do not intend to upgrade your turbo or approximately 250-260 whp. 550cc Injectors are good up to about 300-310 whp. 750cc injectors will be maxed out around the 380-400 whp range. Above 400 whp? Talk to your tuner to determine what injector you should be looking at getting. Regardless of what size injector you go with, you need to tune to adjust for the additional capacity. The ECU has no way to determine what size injectors you have installed and will treat the injector the way it was programmed to. What this means to you is that if you install larger injectors into your car without a tune, your engine will flood with gas and stall.

Spark plugs

Our coupes run Denso Iridium spark plugs. While they are certainly an improvement in spark plug technology they are after all just regular spark plugs with updated materials and design. The main benefit of these plugs is two-fold.

  • First the iridium material used in the electrode is rated for a higher temperature range of operation and greater resistance to corrosion from combustion chamber gases.
  • Secondly the electrode in the iridium plugs tends to be much smaller as the material can handle higher temps without melting away, the smaller center electrode promotes more consistent spark jump as spark ionization has the best chance of occurring when the spark jumps from a sharp edge.
So how are spark plugs part of the modification equation? In very general terms, you should look at running 1-step lower temperature spark plugs for every 75-100 whp that you add. Why? You want your spark plug to stay hot enough to burn off any gunk that may be deposited on it during the combustion process, but if they are too hot they can cause the air/fuel mixture to prematurely ignite during the next compression cycle causing a “knock”. If the air/fuel mixture ignites during the compression cycle it puts undue stress on the valves, piston, rods, engine crankshaft, and weaken the cylinder wall as the engine now is trying to compress the exploding mixture. In extreme conditions where knocking persists, severe engine damage can result.

Exhaust manifold

The exhaust manifold serves two functions on the 2.0T Theta engine. First it collects all of the waste gases pushed out of each cylinder during the exhaust stroke and then directs the exhausted gas into the turbine inlet housing to drive the turbo. As with the intake manifold, the exhaust manifold isn’t a bad design; however, it can be improved with porting an polishing (PnP) to ensure that exhaust gas flows are as smooth as possible maximizing the flow velocity into the turbine inlet. HP gains from PnPing the exhaust manifold are minimal, but if you are looking to squeeze every ounce of power from your upgraded system, this may be a place you can get a little. If you are upgrading your turbo, you may need to change your exhaust manifold to adjust for mounting the new turbo if the new turbo is not specifically designed to bolt on to our exhaust manifold.

To effectively make more than 350 whp, you need to get rid of the OEM TDO4 manifold that has a tiny turbo flange and upgrade to a manifold that has a larger T3 or T4 flange. This also has the benefit of opening up more turbo aftermarket options for you as T3 and T4 turbos are more prolific.

Catalytic Converters

The primary catalytic converter (Cat) also serves as the down pipe from the turbine exhaust and the O2 sensor housing for the ECU. Although catalytic converters have improved since they were introduced in production cars in the mid-1970s, they still represent one of the more significant choke points in the exhaust system. Before you run out and purchase an aftermarket test pipe/ down pipe/ O2 housing to replace that primary or secondary cat, you need to understand that removing a converter from a vehicle, except in order to replace it with another converter violates Section 203(a)(3)(A) of the 1990 Clean Air Act. Section 203(a)(3)(B) makes it illegal for any person to sell or to install any part that would bypass, defeat, or render inoperative any emission control system, device, or design element. With all that said, somebody has to catch you. In many parts of the country vehicles never go through an emissions test so compliance is only really an issue if you sell your car.

Deleting the cats or installing high flow cats can result in reduced back pressure and improved exhaust flow resulting in higher flow rates of exhaust through the exhaust system. Improved flow rates benefits the turbo by allowing exhaust gases to flow more freely through the turbine. On the stock turbo this benefit is minimal as back pressure generally increases with engine RPM in constricted systems long after the stock turbo has maximized its potential to pressurize intake pressures and the wastegate has already opened to bypass excess exhaust gases not needed by the turbo to maintain a constant speed. In other words, you probably don’t need to worry about removing your primary cats if you never intend to upgrade your turbo.

Exhaust system

In normally aspirated engines (NA) you want to keep the flow rate of the exhaust high enough to be able to scavenge excess exhaust gases from the exhaust manifold/headers between exhaust gas releases from the cylinder. This often meant that bigger is not always better for exhaust piping for NA engines as larger piping often results in lower flow rates and higher pressures at low engine RPMS. Although the principle of keeping exhaust flows moving in a turbo engine are the same as a NA engine, the turbo engine has a spinning turbo at the end of the exhaust manifold that keeps exhaust gases flowing smoothly rather than pulsing. The objective of the exhaust system in a turbo engine is to provide the widest path available to eject the waste gases being pushed through the turbo. The freer the flow, the better. The shorter the path the better. And lastly, the straighter the path, the better. In other words, the same principles that applied to the intake also apply to the exhaust.

Oil Catch Can

An oil catch can is used in turbo applications where excessive blow-by (leakage past the piston rings) of combustion gases and oil occurs. This creates a positive pressure in the crankcase. Engine manufactures have placed a valve on the engine block that releases this pressure. This valve is known as a PCV (Positive Crankcase Ventilation) valve. During engine operation, blow-by gases, as well as oil mist from the rotating components of the engine, pass through the PCV valve and are routed back into the intake for the engine to burn off. However, some of the oil mist and other products settle along the engine intake and over time form a "gunk." The oil catch can collects the oil mist and condenses the fuel vapors while allowing "cleaner" gases to be passed back into the intake. Typically, the blow-by gases are passed through a wire mesh, which give the vapor droplets something to adhere to. Since the oil catch cans condense the vapor portion of the gases, they will need to be drained periodically of all the oil, fuel and other contaminants. While an oil catch can does not add anything to the performance of an engine, in the long term it does help to keep the intake system (piping, intercooler, throttle body, intake manifold) clean and free of contaminants that can severely affect engine efficiency.

Super Moderator
40,514 Posts
Discussion Starter #4 (Edited)
Drivetrain Performance

Manual Transmission

If you have an automatic transmission, you are already modded as far as you can go without tearing into the transmission and replacing pieces parts for mucho dinero. The automatic transmission can handle up to about a Stage II tune or roughly, 300-350 ft/lbs of torque before it starts to slip. As with all things Hyundai, your mileage may vary and your transmission may hold more torque or may begin to slip far below the 300 ft/lb mark. Bottom line is that there are no aftermarket bolt-on fixes for the automatic transmission, so there's very little reason to further discuss it on this thread.

There are essentially two modifications that can be performed on the manual 6-speed transmission. The stock clutch on the 10-12 Coupe will begin to slip in the 275-300 ft/lb torque range and sometimes sooner depending on how much wear you have on your clutch. To hold at higher torque levels, you will, as a minimum, need to replace your stock clutch with an aftermarket solution. The decision to replace the dual mass flywheel (DMF) with a single mass flywheel (SMF) is a personal decision if the OEM DMF is in good shape. Certain clutch choices require that you also change out your flywheel as the clutch and the flywheel operate as a matched set.


The OEM DMF is effectively a weight that is fastened to the end of the crankshaft of the engine. The power from the pistons tends to be created in pulses and the weight of the flywheel smooth out these pulses by providing inertia to the rotating engine. Going to a single mass flywheel means that you lose this smoothing effect that the DMF provides and the pulsing is often interpreted as an out of balance condition in the engine. The fact is that the vibration you notice with a SMF was present when the DMF was installed, but the DMF absorbed much of the vibration. Additionally, the inertia of a heavier flywheel makes for a more user friendly manual transmission as the clutch can be engaged at lower engine rpms without causing the engine to stutter and stall. The incorporation of springs between the rotating masses smooth the shift transitions as the clutch is disengaged and engaged between gears.

So, one might ask what the advantage is for installing an SMF. The primary improvement would be a significant loss of weight and improved engine response due to the fact that the engine no longer has to spin a heavy weight on the output side of the crankshaft. The tradeoff is more chatter, vibration, and noise. Additionally, because the heat dissipation rates of a SMF are far better than the DMF, it is better suited to handle high torque load engagements.

On the 10-12 model year coupes, dual mass flywheels work fine as long as the engine remains unmodified and the vehicle is not used beyond manufacturer’s recommendation. When the power output is increased or the vehicle is loaded or raced beyond the design parameters, we often see premature failure of the dual mass flywheel. Dual mass flywheels are tuned systems and must be matched to the engine torque curve, engine resonant characteristics and vehicle load conditions. A significant departure from OEM specs will eventually cause the OEM DMF to fail.


As mentioned before, the OEM clutch on the 10-12 model year coupes will typically start slipping in the 275-300 ft/lb torque range. Most will notice the clutch slipping in the higher gear ranges (typically 4th, 5th, and 6th gear) during a hard pull. You should match the type of clutch you get with your power goals. Getting a clutch that far exceeds your power goals often results in a very unsatisfactory experience. While track and racing clutches will hold substantially more power than a street clutch, heavier pressure plates and stickier clutches often mean heavier clutch pedals and harsher engagements. If your car is primarily a daily driver and your typical drive involves heavy stop and go traffic, a high performance track or race clutch will wear you down quickly.


CHARACTERISTICS: Metal-fiber woven into "organic" (actually CF aramid with other materials), original-equipment style. Known for smooth engagement, long life, broad operating temperature, minimal-to-no break in period. Will take hard use, somewhat intolerant of repeated abuse (will overheat). Will return to almost full operational condition if overheated. Material is dark brown or black with visible metal fibers.

USE: Street-driven cars up to 400hp, auto-x and track use.


CHARACTERISTICS: A high-durability material more resistant to hard use. Engagement is similar to organic, but may glaze slightly in stop-and-go traffic, resulting in slippage until worn clean when used hard again. Higher temp range in general, but can be ruined from overheating - will not return to original characteristics if "cooked". Has a break-in period of 500-1000 miles during which slippage may occur. Care must be taken during this period not to overheat from excessive slipping. Material is uniform yellow/green and may look slightly fuzzy when new.

USE: Street-driven track cars up to 500hp, auto-x and heavy track use. Will take hard use, intolerant of abuse (will overheat and not recover completely). Due to the unforgiving nature of Kevlar, it is not recommended for street cars, especially those that see frequent stop-and-go traffic which will cause surface glazing of the clutch.

Segmented Kevlar

CHARACTERISTICS: Same material and characteristics as solid kevlar above, but segmented (blocks or sections missing) for better heat dissipation. New generation of kevlar offered by UUC is resistant to glazing and is an excellent choice for smooth operation in high-powered cars or those equipped with SMG transmissions.

USE: Street-driven track cars up to 650hp, auto-x, and heavy track use.

Hybrid Carbon/Ceramic/Organic

CHARACTERISTICS: Organic material on one side and a segmented carbon or ceramic material on the other. The idea is that the organic side will help smooth the engagement, reducing the shuddering from the segmented side. Engagement is same as organic, but still with shuddering. Temperature and hp range is identical to organic. Carbon/ceramic side will wear flywheel or pressure plate surface faster and will wear out faster in traffic situations. Material is organic on one side (described above) and segmented or completely separate pucks (described below) on the other.

USE: Can be used in same situations as standard organic. The "hybrid" design appears to be more of a marketing gimmick rather than an actual performance advantage. Some brands are poorly designed and wear unevenly due to flexing of the clutch disk.


CHARACTERISTICS: Very high temperature materials, usually only found on multi-puck disks. Will accommodate 500hp+ Engagement is more abrupt. Will wear flywheel surface faster, especially in traffic situations. Carbon is slightly more durable and flywheel-friendly, ceramic has a higher temp range. Multi-puck design may result in slight shuddering or "stepped" engagement when used in traffic situations, although many users report completely acceptable operation. Material is any of several light hues - gray, pink, brown.

USE: Street/strip applications for drag-racing and heavy track use cars up to 500hp. Will take very hard use, suitable for extreme-clamping applications.

Sintered Iron

CHARACTERISTICS: Extremely high temperature material. Will accommodate 700hp+ Engagement is on or off. Requires special flywheel surface. Material is metallic gray.

USE: Strictly for high-horsepower endurance racing. With correct pressure plate, capable of extremely high clamping force. Engagement is like a switch, either on or off. Does not work well when cold. High-durability flywheel surface required, standard flywheels will be destroyed quickly.​

To repeat the important point, do not buy more clutch than you need. A simple organic disk will handle a wide variety of use - including street use, auto-x, and even true racing. In fact, SCCA ITS racing rules require a standard OE-spec organic disk. UUC has tested organic disks to reliably handle up to 475hp in long-term street use. A kevlar disk is a good choice for a heavily-tracked or road-raced cars, especially with forced induction. Carbon/ceramic should be left to high-power cars that see lots of drag racing, or are dedicated track/drag cars. Sintered iron clutch disks are strictly for endurance racing.

Short Throw Shifter

For you manual transmission types, you may notice that the throws between gears to be a long trip and somewhat imprecise. The OEM shift rod is designed for the average driver who doesn't necessarily need to shift within a fraction of a second and does not want to put a lot of effort into the shift movement. By extending the lever, the shifts require almost no effort; however, you may find that on a quick shift you can accidently throw the transmission into the wrong gear. A short throw shifter is as it implies, a shorter stick with less travel between gears. Although it does contribute to faster and more precise shifts it will require additional effort to get the stick into gear. You can compensate some for the additional effort by adding a weighted shift ball to the shifter that will act as a counter balance and reduce your effort.

Limited Slip Differential

The purpose of the of a limited slip differential is simple… keep the power going to the wheel that has grip and stop wasting effort to spin a wheel that has no grip. Before going into how a limited slip differential works, it would be helpful to understand why a car needs a differential in the first place.

When a car makes a left or right turn, the distance the inside wheels on the turn travel is less than the distance traveled by the wheels on the outside of the turn. Think about your track days… did you want to be on the outside lane of the track or the inside lane on the turns? If your wheels where not allowed to rotate at different speeds and were firmly bolted together to a single drive axle what would happen is that the inside wheels (which are traveling slower) would dominate how fast the axle could turn. The outside wheels in the turn would turn too slow to travel the distance required and drag on the ground.

It is easy to build an axle that drives both wheels at the same speed while being driven by a single drive shaft. It is not as easy to build an axle that allows wheels to turn at different speeds while still being driven by a single drive shaft. The simplest axle requires a gear system that allows for a speed differential between the driven wheels. The simplest solution (and the solution that is found on base and GT Genesis Coupes) is the open differential.

The obvious problem with the open differential setup, as explained in the video above, is that all the power is routed to the wheel that is not “stuck”. This is the reason why when you get stuck in the mud or the snow the wheel that spins is the one that has little or no grip. From a performance standpoint, the left and the right tire will most likely not experience the exact same grip on the left and the right side due to variances in road conditions and tire wear. As a result, the power will tend to go to the wheel that breaks traction first wasting a lot of power that should be used to propel the car forward. This situation can be aggravated if the car is in a turn and the weight shifts from one side of the car to the other due to centrifugal forces. The wheel on the inside of the turn lightens and breaks traction. To prevent this from happening, the differential requires some modification to ensure that both wheels receive power regardless if one starts to slip or not. There are several methods of limiting the slip of an open differential, but we will only be covering how the Torsen limited slip differential in the R-Spec and Track models of the Genesis Coupe work.

Do you need a limited slip differential?

Although all cars can benefit from a LSD, the cars that would benefit most would be either cars that are frequently operated in low traction environments or cars that are built to pull every ounce of the power produced by the engine to propel the car forward. How much you will benefit from a LSD is directly related to what your performance expectations are. In ideal driving conditions there is little or no benefit for a LSD. In most situations, you can forego the cost of upgrading an open differential to a limited slip differential and use the money you have saved to purchase an upgrade that will provide a better return on your investment.

Note: If you are interested in getting in the sport of drifting, you really need a limited slip differential. Successful drifting requires that you break both rear drive wheels loose to maintain a controlled drift. Although you can drift with an open differential, in most cases what will happen is that you will only be able to break one tire loose while the other tire drags on the ground making it extremely difficult and sometimes impossible to maintain and/or control the drift.

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40,514 Posts
Discussion Starter #5 (Edited)
Suspension and Handling


There are two different types of braking systems that are found on Genesis Coupe in captivity and in the wild. What is important to understand is that both brake systems provide adequate stopping power for daily driving and spirited driving situations. Both brake systems will apply enough braking force to activate the anti-lock braking system (ABS) on dry pavement with good tires. Any additional braking ability will not stop your car faster.

So, the question probably still lingering in your mind is, “why offer Brembo brakes on the Track and R-Spec models when the base brakes do just as well?” This is one of those situations where the term “Because race car”. Bigger brakes work better in situations where the brakes are used frequently and hard such as on a track. When brakes are used hard they tend to heat up and lose effectiveness through two mechanisms… first the brake pad itself will leave deposits on the brake disk when they are heated up which in turn reduce the contact surface between pad and disk… second the brake fluid itself can get so hot that it will boil inside of the caliper releasing trapped air which creates a “sponginess” in the brake feel.

Brake calipers

The brake caliper converts fluid pressure to mechanical pressure necessary to press the brake pad against the brake rotor through a set of pistons in the caliper. Obviously the bigger the brake caliper, the more pistons that can fit in the caliper housing, the more force that can be applied to the pad. Brembo brakes use a mono-block style 4 piston caliper and non-Track/R-Spec models use single piston floating type caliper. As mentioned before, under normal circumstances both Brembo and non-Brembo brakes have the same stopping power and the larger calipers are not necessary in daily driving scenarios. With that said, changing the unsprung and sprung weight of the car can have a dramatic effect on how effective your brakes work. For instance, a larger/heavier wheel will require more braking force to reduce speed as a larger wheel will store more rotational energy than a smaller wheel. This is where the bigger brakes shine as the extra force required is readily available.

Brake pads

If all of your driving performance comes down to the four little rubber contact patches on the ground, certainly the pads that contact the spinning rotor that stops the car limit your stopping performance. As with clutches, brake pads come in different compositions. Each type of pad has their advantages and disadvantages. As with your clutch decision, choosing the right type of brake pad will depend heavily on how you plan to use your car. Pads that work well under track conditions will not work well in a daily driven car and vice versa.


Organic pads are made of fibers mixed with fillers and binding resins to hold them together. Some components commonly found in organic pad are glass, Kevlar, and carbon. Organic pads have what enthusiasts consider a ‘mild’ character. They tend to be softer, easier on rotors, and they don’t make much noise. In the US, most OEM’s ship organic pads in new cars because they don’t require a lot of heat to generate friction, or bite. They are therefore safe for commuting in various environments. While these pads offer comfort, their Achilles Heel is a severely limited temperature range. Once they reach their maximum operating temperature, they almost immediately lose their coefficient of friction and burn up very quickly. Even if your brakes do not burn up, extreme heat can glaze the contact surface of the pad making them less effective over time.

The materials used in these pads are the least costly to acquire, as are the tools and processes to manufacture them. Therefore, organic pads are typically the least expensive pad type.


Not surprisingly, semi-metallic pads get their name from their composition. Each friction puck contains a substantial amount of metal. Common ingredients are steel wool, iron, or copper, mixed with fillers, friction modifiers, and lubricants such as graphite. On the plus side, these pads have higher operating temperatures than organic pads, draw heat out of the rotors, and do not wear as quickly. On the other hand, they are more abrasive and tend to wear rotors more quickly, make more noise, produce heavier dust, and many times have very little cold bite. Most race pads on the market today are semi-metallic.

Because the constituent materials, tools, and processes involved are more expensive than those used to produce organic pads, semi-metallic pads are more expensive.


The term ‘ceramic’ has been a hot marketing buzzword in brake pads for the past decade. These pads are created by mixing ceramic fibers, fillers, and bonding agents. The greatest benefits of ceramic pads are their lack of dust and noise. They tend to wear a little longer than organic compounds, and are also a bit more rotor-friendly. While they may have a higher temperature threshold than some of the organic compounds, they cannot compete with semi-metallic or sintered pads for heavy duty use. Enthusiasts who spend a disproportionate amount of time staring lovingly at their 6” polished rim lips may enjoy ceramic pads. Those who prefer to actually drive their car hard may be disappointed with the performance of ceramic pads.


While sintered pads have been popular on motorcycles with steel rotors, they remain an emerging technology for automotive use. Most sintered pads are formed from a copper alloy powder. The powdered metal is mixed with other lubricating and wear controlling constituents such as graphite and carbon, formed into the required shape, and then brazed to a backing plate at temperatures as high as 1800 degrees F.

Sintered pads have some unique characteristics vs. other pad types. Their nearly pure metal content provides a stable coefficient of friction from cold to hot, meaning they often need almost no warm-up time to produce bite. Since they are formed at extremely high temps, they don’t fade under extreme use. They also don’t create as much of a transfer layer on rotors, and therefore don’t require a lengthy, traditional bed-in procedure. Since the pads are semi-porous, they can be used in any weather condition: rain, snow, mud, etc.

Because they are mostly metal, the negatives traditionally associated with sintered pads have been increased rotor wear, noise, and the transmission of heat into the calipers.

The materials, tools, and processes involved with producing sintered pads are the most expensive of all current pad types.​


Your rotors are the other half of the braking equation as they are the surface that the pads must contact to stop the car. Under normal usage, your stock brake rotors will work well over the life of the rotor with no modification required. Just as with your brake pads, heavy brake usage can lead to superheating your rotors. While the rotors themselves will handle the heat generated just fine, the brake pad can suffer tremendously coming into contact with a hot rotor and leave deposits on the rotor that in turn can have an impact on braking performance. These deposits on your brake rotor will lead you to believe that the rotor itself has warped as the braking action tends to pulsate as the pads grip the unaffected parts of the rotor and lose grip on the parts that have pad deposits on them. There are essentially three different aftermarket modifications available for the brake rotor specifically targeted at cooling the rotor while in use and reducing the amount of deposit left on the rotor by the brake pad that result from overheating.

Drilled rotors

Drilled brake rotors, as the name implies, have holes drilled in them. Having a holes drilled into any of your brake parts may seem counterintuitive, especially the brake rotors (after all, a rotor full of holes means that there's less surface area for the brake pads to grab and stop the car) but there are a few reasons drilled rotors make sense.

The first is heat. When the brake pad grabs the rotor, it creates friction, which creates heat. If that heat cannot escape, it leads to brake fade, which reduces the brakes' stopping power. The second reason is gas build up. This actually is not much of a problem anymore; however, the materials used in some older types of brake pads caused gas to build up between the rotors and pads. That gas also limited stopping power. The last reason is water. If a car drives through a puddle, a carwash or even a rainstorm, the brake rotors can get wet. A wet brake rotor is slippery and difficult for the brake pads to grab. Having drilled holes on a brake rotor makes it easy for heat, gas and water to be quickly moved away from the rotor surface, keeping the brake performance strong.

The downside of using drilled rotors on your vehicle is that all of those holes tend to weaken the rotors (just like punching holes in the wall of a house would weaken the wall). After repeated stressful driving, the rotors can even crack and fail.

Slotted rotors

Slotted brake rotors use slots carved into the flat metal surface to move gas, heat and water away from the surface of the rotors. You can think of the slots as irrigation ditches that move the unwanted materials safely out of the way.

Slotted brake rotors are popular with performance car drivers because the type of driving they do puts a lot of stress on the rotors. As previously mentioned, drilled rotors have been weakened, which makes them prone to cracking around the holes, particularly when they've been repeatedly driven hard. Because they tend to be a little more durable than the drilled brake rotors, slotted brake rotors may be a better brake part choice for some performance car drivers.

Of course, slotted brake rotors are not perfect, either. They tend to wear down brake pads very quickly. Because of this, the most common type of performance brake rotors found on production performance cars are of the drilled variety. While that type of construction is seen as too weak for racing applications, most everyday drivers should have no trouble with drilled rotors on their street cars and can save the slotted rotors for cars that are racetrack-bound.

Slotted and drilled rotors

If one is good then two are better, right? Ummm… not so much. What you end up doing with slotted and drilled rotors is amplify all the disadvantages of both types of rotors while not gaining any additional advantage that each type of rotor offers. From a performance standpoint, having slotted and drilled rotors serve no purpose. From a show standpoint they sure look cool. Slotted and drilled rotors fit right up there with other aesthetic decisions that we will discuss in a later segment; however, have no performance benefit beyond what was stated above for each individual type of rotor​
Material composition and quality

The term “you get what you pay for” is probably no truer than the purchasing of brake rotors. Can you find them cheap? Answer: Yes; however, the material composition and workmanship quality between the lowest end rotors and the highest end rotors are like night and day. By saving money today you could very well be risking your life tomorrow if the rotors you purchase fail when you need to stop. Regardless of which type of rotor you decide to go with, do not buy cheap Chinese knockoffs trying to save a few bucks.

Stainless Steel Brake Lines

Okay… so you’ve upgraded your calipers, pads, and rotors on your racecar, what’s left? As with most things related to performance, when you increase the strength of one component and push the edge, you reveal a weakness in another component. The last component left to upgrade is the rubber brake lines to a stainless steel braided line. Rubber lines will tend to expand in hard braking situations reducing the braking effectiveness. This is especially true as the fluid inside of the brake lines are heated up by the braking action and soften the rubber line. Stainless steel braiding prevents the brake line from expanding and contracting thus improving brake response and making braking more consistent.

Does the fluid matter?

Short answer, is “it depends”. As mentioned before, the brake fluid heats up inside of the caliper as the brakes are used. If the brake caliper gets hot enough to boil the brake fluid, air bubbles are released that impact the braking effectiveness. There are several DOT 4 compatible brake fluids that contain additives that increase the boiling temperature of the fluid; thus, potentially reducing the possibility that the fluid will boil. Keep in mind that normal daily driving situations with occasional hard braking requirements is not enough to get the brakes hot enough to boil the regular DOT 4 brake fluid that is in your system. Racing brake fluid is quite expensive and the cost may not be justified by your driving habits. With that said racing fluid will not adversely impact the performance of your brakes either.

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Discussion Starter #6 (Edited)
Suspension and Handling (continued)


As previously mentioned the performance output of everything that you do to your engine, drivetrain, and suspension comes down to four little rubber patches on the ground. If your tires cannot hold the ground, it does not matter what the rest of your car is capable of doing. Unlike with other components, price is not necessarily an indicator of how good a tire is. What you have to concern yourself with is how the tire will perform in the driving conditions you intend to use them in. It all comes down to essentially two things: material composition of the tire and tread pattern.

Material composition

The objective of this article is not to make you a tire expert. Fortunately, for you there are other ways to determine if a tire is right for you without understanding the physics and chemistry used to develop a tire. In your search for the ideal tire, you first have to answer a question of yourself: How do I intend to use the tire? Before you jump on an answer consider that your tire use is going to depend on several factors such as time of year, speed, cornering requirements, and surface conditions.

Summer tires: As the name may imply, summer tires are intended to be used in the warm months when there is ideal driving conditions on dry pavement. Summer tires, if used in the correct environment, tend to be the stickiest tires of all the tire categories and will give you the best overall performance and grip characteristics. Depending on their tread design, summer tires can provide superior grip along with performance even on wet pavement. Because of their relative hardness and heat shedding characteristics, summer tires usually last longer than any other tire category. The downside of this hardness is the fact that they get even harder as the temperature drops. Eventually the tire will get so cold that it will no longer conform to the road surface, reducing the contact patch, and losing grip. The higher the performance of summer tire that you get the less cold tolerant the tire gets. Keep this in mind if you live in an area that is cold more than it is hot.

Winter/snow tires: While some may believe that the tread is the main difference between winter and summer tires, they would be mistaken. As stated previously, summer tires are soft in the heat but get hard in the cold affecting the contact patch. A winter tire’s composition keeps the tire soft in the cold and allows for the tire to better conform to a cold surface thus improving grip in the cold. The difference between winter and summer tire performance in the cold is dramatic. The downside of winter tires is that they tend to get too soft when things warm up and wear very quickly. Summer tires tend to improve grip on dry surfaces as they wear because the contact surface increases. The treads on a summer tire provide a channel to evacuate water when the surface is wet. The grip characteristics of a winter tire depends heavily on the tread, as the tread provides a means for the tire to compact snow to get as much rubber in contact with the surface as possible. Worn winter tires lose effectiveness over time.

All season tires: It would seem that a tire that is designed for “all seasons” would provide the best of all worlds in terms of grip and performance. The truth of the matter is that all season tires do just “okay” in all seasons but do not come close to the performance capabilities of their summer and winter counterparts; however, may perform better in that “in between” state where summer tires lose effectiveness but it is not quite cold enough to justify installing winter tires. Additionally, not all “all season” tires are created alike… some are designed for high end performance and thus tend to lean towards better performance in summer-like conditions while others lean towards better cold performance. No all season tire can be everything to everyone. All season tires will provide adequate performance to handle most daily driving situations and could potentially be the tire of choice for the majority of drivers who do not push the tire’s performance to the edge.​
Directional vs. non-directional tread

Some tire tread designs focus heavily upon wet surface operation. Many of these tread designs are “directional”, meaning that the tire is designed to be mounted on the wheel rotating in a certain direction. If you look at a directional tread pattern, you will notice that the tread channels direct water from the inside of the tire to the outside of the tire and tend to be very effective at evacuating water from underneath the tire to allow for the tire to maintain its contact patch on the surface rather than riding on top of the water (read: hydroplane). Non-directional tread patters can be quite effective at evacuating water; however, do so by channeling the water to the back of the contact patch rather than continuously pushing water away from the tire. Non-directional tires can quickly be overwhelmed by deep water allowing the tire to float on the water instead of cutting through it.

Although directional tires are more effective on wet surfaces, care should be taken before making the commitment to purchase them. On a square setup, directional tires must be rotated front to back to maintain the same rotation of direction; however, the Genesis Coupe’s OEM configuration is a staggered setup. What this means is that the front tires are narrower than the rear tires. This staggered configuration favors rear wheel drive cars by increasing the contact patch of the rear drive wheels while minimizing the steering resistance of a wider tire on the front wheels. The disadvantage of the staggered configuration is that tires must be rotated left to right because the front and rear wheels are different sizes. Because a directional tire cannot be rotated left to right easily, it often means that you cannot rotate your tires which will lead to more frequent tire changes due to wear. The only way a tire can be rotated on a staggered setup is if you unmounts each tire and swap them left to right while maintaining the proper rotational direction. The ROI depends greatly upon how much a new set of tires will cost you. The more expensive the replacement tire, the more it makes sense to pay the extra money to swap your tires on at the midpoint of their wear.

How to read all that stuff on the sidewall of your tire… or decoding the UTQG (Uniform Tire Quality Grade).

Treadwear Grades

UTQG Treadwear Grades are based on actual road use in which the test tire is run in a vehicle convoy along with standardized Course Monitoring Tires. The vehicle repeatedly runs a prescribed 400-mile test loop in West Texas for a total of 7,200 miles. The vehicle can have its alignment set, air pressure checked and tires rotated every 800 miles. The test tire's and the Monitoring Tire's wear are measured during and at the conclusion of the test. The tire manufacturers then assign a Treadwear Grade based on the observed wear rates. The Course Monitoring Tire is assigned a grade and the test tire receives a grade indicating its relative treadwear. A grade of 100 would indicate that the tire tread would last as long as the test tire, 200 would indicate the tread would last twice as long, 300 would indicate three times as long, etc.
The problem with UTQG Treadwear Grades is that they are open to some interpretation on the part of the tire manufacturer because they are assigned after the tire has only experienced a little treadwear as it runs the 7,200 miles. This means that the tire manufacturers need to extrapolate their raw wear data when they are assigning Treadwear Grades, and that their grades can to some extent reflect how conservative or optimistic their marketing department is. Typically, comparing the Treadwear Grades of tire lines within a single brand is somewhat helpful, while attempting to compare the grades between different brands is not as helpful.

Traction Grades

UTQG Traction Grades are based on the tire's straight line wet coefficient of traction as the tire skids across the specified test surfaces. The UTQG traction test does not evaluate dry braking, dry cornering, wet cornering, or high speed hydroplaning resistance.

The Traction Grade is determined by installing properly inflated test tires on the instrumented axle of a "skid trailer." The skid trailer is pulled behind a truck at a constant 40 mph over wet asphalt and wet concrete test surfaces. Its brakes are momentarily locked and the axle sensors measure the tire's coefficient of friction (braking g forces) as it slides. Since this test evaluates a sliding tire at a constant 40 mph, it places more emphasis on the tire's tread compound and less emphasis on its tread design.

In 1997, the UTQG Traction Grades were revised to provide a new category of AA for the highest performing tires in addition to the earlier A, B and C grades. Previously the A grade had been the highest available and was awarded to tires that offered wet coefficients of traction above 0.47 g on asphalt and 0.35 g on concrete. Today the grades and their traction coefficients are as follows:

Temperature (Resistance) Grades

The UTQG Temperature Grade indicates the extent to which heat is generated/ or dissipated by a tire. If the tire is unable to dissipate the heat effectively or if the tire is unable to resist the destructive effects of heat buildup, its ability to run at high speeds is reduced. The grade is established by measuring a loaded tire's ability to operate at high speeds without failure by running an inflated test tire against a large diameter high-speed laboratory test wheel.
Every tire sold in the United States must be capable of earning a "C" rating which indicates the ability to withstand 85 mph speeds. While there are numerous detail differences, this laboratory test is similar in nature to those used to confirm a tire's speed ratings.

Unfortunately for all of the money spent to test, brand and label the tires sold in the United States, the Uniform Tire Quality Grade Standards have not fully met their original goal of clearly informing consumers about the capabilities of their tires. Maybe it's because tires are so complex and their uses can be so varied, that the grades don't always reflect their actual performance in real world use.​
Speed Rating

In Germany some highways do not have speed limits and high speed driving is permitted. Speed ratings were established to match the speed capability of tires with the top speed capability of the vehicles to which they are applied. Speed ratings are established in kilometers per hour and subsequently converted to miles per hour (which explains why speed ratings appear established at "unusual" mile per hour increments). Despite the tire manufacturer's ability to manufacturer tires capable of high speeds, none of them recommend the use of their products in excess of legal speed limits. The maximum operating speed of a vehicle must be limited to the lowest speed rated tire on the vehicle.

Speed ratings are based on laboratory tests where the tire is pressed against a large diameter metal drum to reflect its appropriate load, and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire's required speed has been met.

It is important to note that speed ratings only apply to tires that have not been damaged, altered, under-inflated or overloaded. Additionally, most tire manufacturers maintain that a tire that has been cut or punctured no longer retains the tire manufacturer's original speed rating, even after being repaired because the tire manufacturer can't control the quality of the repair.

Over the years, tire speed rating symbols have been marked on tires in any of three ways shown in the following examples:

225/50SR16 225/50SR16 89S or 225/50R16 89S

Each of these was an acceptable method of identifying speed ratings.
Early tires had their speed rating symbol shown "within" the tire size, such as 225/50SR16. Tires using this type of branding were not to have been produced after 1991.

225/50SR16 112 mph, 180 km/h
225/50HR16 130, 210 km/h
225/50VR16 in excess of 130 mph, 210 km/h

Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S. The most common tire speed rating symbols, maximum speeds and typical applications are shown below:

When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities.

While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed.

Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below:

As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tires capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.

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40,514 Posts
Discussion Starter #7 (Edited)
Suspension and Handling (continued)

Tire Size Guide

The tire size branded on the sidewall provides a significant amount of information about the tire's intended purpose, dimensions, load capacity and high temperature/high speed durability.

My primary example will be based on variations of the 225/50R16 size, although other sizes will appear where appropriate.

Service Type

Most tire sizes begin with a letter or letters that identify the type of vehicle and/or type of service for which they were designed. The common indicators are as follows:

P225/50R16 91S

P = When a tire size begins with a "P," it signifies the tire is a "P-metric" size that was designed to be fitted on vehicles that are primarily used as passenger vehicles. This includes cars, minivans, sport utility vehicles and light duty pickup trucks (typically 1/4- and 1/2-ton load capacity). The use of P-metric sizes began in the late 1970s and they are the most frequently used type of tire size today.

225/50R16 92S

If there isn't a letter preceding the three-digit numeric portion of a tire size, it signifies the tire is a "Metric" size (also called "Euro-metric" because these sizes originated in Europe). While Metric tire sizes are primarily used on European cars, they are also used on vans and sport utility vehicles. Euro-metric sizes are dimensionally equivalent to P-metric sizes, but typically differ subtly in load carrying capabilities.

Section Width

Following the letter(s) that identify the type of vehicle and/or type of service for which the tire was designed, the three-digit numeric portion identifies the tire's "Section Width" (cross section) in millimeters.

P225/50R16 91S

The 225 indicates this tire is 225 millimeters across from the widest point of its outer sidewall to the widest point of its inner sidewall when mounted and measured on a specified width wheel. This measurement is also referred to as the tire's section width. Because many people think of measurements in inches, the 225mm can be converted to inches by dividing the section width in millimeters by 25.4 (the number of millimeters per inch).

225mm / 25.4 = 8.86"

Sidewall Aspect Ratio

Typically following the three digits identifying the tire's Section Width in millimeters is a two-digit number that identifies the tire's profile or aspect ratio.

P225/50R16 91S

The 50 indicates that this tire size's sidewall height (from rim to tread) is 50% of its section width. The measurement is the tire's section height, and also referred to as the tire's series, profile or aspect ratio. The higher the number, the taller the sidewall; the lower the number, the lower the sidewall. We know that this tire size's section width is 225mm and that its section height is 50% of 225mm. By converting the 225mm to inches (225 / 25.4 = 8.86") and multiplying it by 50% (.50) we confirm that this tire size results in a tire section height of 4.43". If this tire were a P225/70R16 size, our calculation would confirm that the size would result in a section height of 6.20", approximately a 1.8-inch taller sidewall.

Internal Construction

P225/50R16, P225/50ZR16

The R in the P225/50R16 91S size identifies that the tire has a Radial construction in which the tire's body plies "radiate" out from the imaginary center of the wheel. Radial tires are by far the most popular type of tire today representing over 98% of all tires sold.

Tire and Wheel Diameter

P225/50R16 91S

The 16 indicates the tire and wheel diameter designed to be matched together. Tires that have a rim diameter expressed in inches (P225/50R16, as well as 8, 10, 12, 13, 14, 15, 17, 18, 19, 20, 22, 23, 24, 26 and 28) are called "inch rim" sizes, are the most common type of tire size and are used on most cars, minivans, vans, sport utility vehicles and light duty light trucks.

Enough about tires... what about Coilovers, Bags, and Springs?

One of the things you may hear from modern car enthusiasts is, "Your wheel gap makes me puke." What they are talking about is all that space that the car manufacturer gave you between the top of your wheel and the top of the wheel well. The cure is to lower your suspension and get closer to the ground. There are two popular methods of lowering your car: Springs and Coilovers. The third method of lowering your car is on airbags or some other kind of air lift system. The latter method is quite expensive and more of a show option than a practical method of lowering your car.

Springs: First off.... never ever cut your OEM springs to get a lower profile. Your OEM springs are progressive springs that start out relatively loose and get tighter as they are compressed. Cutting the springs changes the handling characteristics of the springs and what you will end up with is a car that has four corners doing their own thing when you drive. With that said, there are a number of aftermarket alternatives available to you at a relatively low cost that can help you do the job right the first time and have a predictable drop and handling characteristics. This thread is not about recommending vendors or manufacturers, so do me a favor and don't ask; rather, determine what kind of drop you are looking for and then ask a vendor what springs will help you reach your goal.

One item to note about dropping your car by changing just the springs: Your ride is going to suck! While the springs control your ride height there is another component in your suspension that controls the quality of the ride and that is your struts. On the front axle, the struts and the coil springs are one assembly. The back axle is a multilink suspension and the strut is separate from the coil spring. Regardless if we are talking about front or back springs, the strut is designed to work at stock height; as a result, lowering your car will compress the strut all of the time. Additionally the strut travel is set to work with the stock springs and will not compress far enough when you hit a bump. If you are lowered on springs and you hit a big enough bump (read: railroad tracks)... you will hit the bump stop on the strut and your ride will be somewhat similar to the ride the Pioneers of early America felt in their Conestoga wagons blazing trails across the great plains.

Coilovers: There are two types of coilovers available on the Genesis Coupe. The budget coilovers duplicate the stock suspension. In other words, a combined assembly in the front and a component assembly in the rear. The higher end coilovers have combined assemblies for both front and back. Coilovers offer two advantages over springs: First, the strut can be lengthened and extended to match the spring height so that strut travel ceases to be an issue; Second, the dampening rate of the strut can be adjusted to give you a softer or harder ride. While adjusting the combined assembly in the front on budget coils is relatively easy (just change the length of the strut and you are done), adjusting the ride height of the multi-link component setup in the rear is a pain in the butt because you have to adjust both the spring height and the strut height separately to ensure that the preload (preset position of the strut) is maintained. So, if you plan on changing your ride height frequently, do yourself a favor and get a combined assembly for the rear axle too. You will thank me if you do.

Bags: In cases where you raise and lower your car very often, coilovers may not be a viable option for you. There are a number of airbag/airlift systems available for the Genesis Coupe that will allow you to raise or lower your car with the press of a button. While this may sound convenient, the trade off is a lighter load of cash in your wallet as most airbag systems will run over $2000 per axle. If you are seriously considering airbags as an option, you are probably reading the wrong article. One other advantage that comes from being able to easily raising and lowering your car is that you are probably going to drive it at a reasonable height that doesn't involve leaving low lying parts on the road behind you or producing sparks as you drive. One can never underestimate the value of not scraping the heads of ants at 35 mph.​

In all cases where your car is lowered, you are changing the aspect ratio of the stock suspension in a way that the manufacturer had not intended. The inevitable result is that you will change the handling characteristics of the car. In some cases, you will increase or amplify the shortcomings of the stock suspension and in other cases you may improve the handling (for instance lowering the CG of the car). In all cases your ride will never be as smooth as the stock ride. If you find that the car is very stiff and somewhat uncomfortable to drive on long journeys, you may want to reconsider lowering your car and just deal with all "those guys" who keep giving you crap about riding at SUV height. Ride height is like a woman's shoes. To look good, a woman will put up with a certain level of discomfort; however, the older she gets the more "comfortable" shoes seem like a better option. You can't have both.

Wheels - You need them because cars look stupid without them.

I was originally not planning to cover wheels in this thread because there is really no way to answer every possible wheel question; however, probably the most frequently question asked on this forum is "will these wheels fit?" So, I will use the little space I have here to go over some of the basics without getting into too much detail. A link is provided below that will take you to a thread that covers everything you ever wanted to know about wheels.

Wheels fall into the category of both a performance mod and an aesthetic mod depending on what your goals are with regard to how you plan on using your car. If "go fast" is your goal, smaller lighter wheels will help you get to where you are going. This is because the torque that is initially applied when you give the car a little gas will have to turn the wheel. (<duh>, right?) The heavier the wheel, the more energy that is required to get the wheel to turn. The other thing that you want to consider is that you do not really want to change the overall diameter of the wheel (wheel + tire) or you can really mess with your speedometer indication and could potentially end up with issues with the car's traction control system (TCS). If your goal is to change the look of the car, weight and rolling diameter is not going to be as much a factor. For daily driving, comfort and handling may be a concern, so a large wheel + low profile tires (to maintain the overall rolling diameter of the wheel) may not be your first best choice because there is less sidewall to absorb shock in this setup. Remember that all modifications work together for a total look and/or a total feel and very often a modification can affect other aspects of how the car handles and performs. Before jumping on a wheel modification from stock wheel sizes, think carefully about how this change will impact how you use your car and how it will affect your ride quality and handling characteristics.

It would be nearly impossible to discuss in this thread all the possible wheel combinations that work (or don't work). Aside from that, there is an entire thread that is dedicated to discussing these combinations that was started back in 2009. There is a pretty good chance that this one thread covers just about everything you need to know about what fits and what doesn't. What you need to know when buying wheels is that the bolt pattern is 5 x 114.3mm and the center bore is 67.1mm. Beyond this, you need to go to this thread: and do some serious reading before posting a thread that asks, "Will these fit?"

Offset designed wheels or spacers?

For those folks who are looking for that wide stance and hellaflush look you are probably going to be wondering how to gain that look. (Hint: it takes more than just wide tires) First off, it doesn't matter if you pull the look off with wheel spacers (spacers that sit in between the hub and the wheel) or if the wheel was designed with the offset in place. The load on the wheel hub is the same. Second, you are looking for wheels that have a positive offset. A neutral or negative offset will push the wheel outside of the wheel wells making your car look more like a Jeep. Lastly, the amount of offset you will require will depend greatly upon the width of the wheel. As you increase the width, you must lower your offset to compensate or the inside of the wheel will start rubbing on important stuff like your strut. Again, refer back to the wheel thread I posted above for more information about offsets and wheel widths.

Offset explained!

Sub-Frame Rigid Collars

There is a phenomenon that up to a few years ago was relatively unknown in the performance world and that was the mysterious "play" that occurred between the suspension sub-frame and the car frame that was a result of a manufacturing shortcut that manufacturers used to speed up the assembly process. This discovery led to the development of the sub-frame rigid collar that essentially removes all of that play and stiffens up the entire frame of the car.

With that said, a number of vendors on Gencoupe have sub-frame rigid collars for sale for under $100.00. I cannot explain the science that makes these sub-frame collars work nor vouch for the foundational explanation of how they work; however, I cannot argue with the results. The results of installing these rigid collars will significantly improve your ride quality.

Super Moderator
40,514 Posts
Discussion Starter #8 (Edited)
Bolt on Modifications

Okay, now that we’ve covered the basics as to what components can be modified, let’s talk specifically about how these parts can be modified and what kind of performance you can expect to get. Again, I would reiterate that I am primarily targeting the turbo community out there simply because that is what I own and know best and the 2.0T is where you are going to get the most bang for the buck. With that said, if someone wanted to do a forced induction (turbo or supercharger) modification to their 3.8, much of the information in this thread will apply to them as well. In many cases, many of the modifications discussed here have been discussed in detail elsewhere. Whenever that is the case, I will provide a link to the detailed thread and will only touch the surface of the modification in question. We will start with the simplest modifications first and work on down to the more complicated ones further down the thread.

Magnuson–Moss Warranty Act - (Only applies in the United States)

Probably the most frequently asked question with regard to modding is, “Will this modification void my warranty?” The answer to this question is that we are protected by the Magnuson–Moss Warranty Act that was enacted in 1975 to protect consumers from being forced by manufacturers to only purchase from them. With that said, although the manufacturer cannot void an entire warranty because you used an aftermarket replacement part, that does not mean that the manufacturer cannot deny a damage claim if they can reasonably show that the cause of the failure is related to the improper operation or installation of a non-covered part. For instance, say your turbo receives some foreign object damage because something was sucked into the intake and the aftermarket filter did not prevent the object from entering the intake. The manufacturer is not liable for the damage to the turbo due to the failure of the aftermarket filter. If, however, your stereo stops working, the manufacturer cannot reasonably connect the intake filter to the operation of the stereo and the manufacturer is still responsible for honoring their warranty.

The Magnuson–Moss Warranty Act is not a panacea for all things related to warranty repairs, and in many cases a manufacturer may attempt to deny a claim in hopes that you will quietly accept their verdict without pushing legal action. The question that you have to ask yourself, and you have to be honest with yourself when you answer, “Did my modification cause the failure?” If you cannot reasonably rule out your modification, then accept the fact that you may be responsible for the damage and move on. If you cannot connect the failure to the damage… keep pushing. The dealer will escalate the problem to the manufacturer who will evaluate the failure and provide an official verdict as to whether the damage is covered by warranty or not. If you lose the verdict you may have to take legal action to get the manufacturer to honor the claim.

Do I need an intake modification?

All modifications come down to “what are your goals?” You may want to do an intake mod to make room for performance gains or you may simply want to better hear your turbo spooling. Yes, that’s right… an intake modification will make your turbo louder! There is a metal silencer in the stock intake that does a pretty good job masking the sound of the turbo spooling and the associated bypass valve “whoosh” sound when it opens and dumps the charged pressure from your intercooler piping back into the intake. You can get some of that sound without changing your intake by gutting the silencer.

As discussed before, you have essentially two aftermarket choices for intakes. The short ram intake (SRI) is the shortest path to the inlet of the turbo. The disadvantage, if any, is that the filter intake is located in the hot engine bay and some of that hot is going to be sucked into the intake. Many SRI setups come with an air dam that will isolate the filter from the hot engine bay air. Some will provide ducting from the factory ram air intake to bring in fresh cool air from the outside.

A cold air intake (CAI) has longer intake tubing to allow the intake to drop down behind the front bumper to pull in cool air from the front of the car and from underneath the car. The additional length of tubing to reach the front bumper is almost negligible in most setups and the CAI will never pull in hot engine bay air. As discussed before, there is a danger that a CAI that sits very low in the bumper can accidently be submerged in deep water, suck in a large amount of water, and cause the engine to hydrolock. This scenario is not completely unlikely and several owners have destroyed their engines while using CAIs.

There are more examples, but you get the idea. The CAI is really a fair weather intake solution and you should be extremely careful if you have a CAI and operate your car in wet conditions. If you decide you just absolutely have to have a CAI and that no other intake will do, at least take the precaution of installing an air bypass valve and a hydroshield. The air bypass will open if there is a blockage at the filter (water qualifies as a blockage). Keep in mind for you turbo guys that the amount of air that can be sucked in through the bypass valve is limited; thus it would be best if you didn't rev your engines going through a puddle. The hydroshield is a bit of technology that is effective in keeping the filter dry if it is sprayed (not submerged) with water. Keeping your filter dry is important to ensure proper flow. In fact, it works so well, I recommend it for those of you who are running any aftermarket intake (SRI or CAI) to protect your filter from water spray.

Do I need a BOV?

Like with the intake, there are a number of non-performance related reasons for purchasing a BOV. Technically speaking, you do not need a BOV unless your stock BPV is no longer doing the job. If your BPV fails, it will fail open and you will not be able to build boost. Generally speaking, you will hear a fluttering sound during partial throttle or high RPM pushes if your bypass valve is leaking. If you hear a metallic fluttering sound, especially when you let up off the gas, do not drive your car until you determine what the problem is.

Aftermarket BOVs/BPVs can be mounted in the stock BPV location, on the hot side pipe or on the cold side pipe. The mounting location will have no effect on how the BOV works. Some BOVs are designed to use the stock solenoid valve that is controlled by the ECU to open and close others will use any available vacuum source. A quality BOV, regardless of manufacturer will do the job that it needs to do and the choice really comes down to personal preference with regard to how the BOV sounds. Stay away from eBay budget BOVs made in China.

What is a manual boost controller and do I need one?

The turbo’s wastegate is normally controlled by the ECU through the turbo boost solenoid valve located above the power steering module. The purpose of the wastegate is to keep the turbo from overspeeding and surging beyond the programmed pressure as set by the ECU or a manual boost controller.

A manual boost controller bypasses the ECU controlled boost solenoid valve and allows for manual control of the wastegate actuator. The manual boost controller can be manually set to allow boost signal pressure that comes from the compressor section of the turbo to open the wastegate at a manually set pressure. The advantage of the manual boost controller is that you can manually set the boost level without regard to what the ECU is programmed for… this is also a disadvantage if the ECU cannot compensate for the set pressure by adjusting timing and adding fuel to compensate for the additional air. Generally speaking, you should not install or use a manual boost controller unless you have a tune that supports one or you can tune your car using a piggyback device such as CMD or a full plug and play ECU like the Haltech.

A variation of the manual boost controller that adds a level of convenience to the operator is the electronic boost controller that allows the operator to remotely adjust maximum boost levels through a control panel in the cockpit. More sophisticated electronic boost controllers have presets that can adjust pressure based on engine RPM, allowing for a slower spool on the low end to limit the immediate and sudden punch of boost.

What should I look for in an aftermarket intercooler?

There are three things you need to pay attention to when evaluating any aftermarket intercooler:

  1. Size – While you can get an intercooler that will sit in front of your car like a giant aluminum battering ram, bigger is not always better. Keep in mind that the space inside of the intercooler will pressurize to the same pressure as the rest of the charged system… bigger means a larger volume of space that will need to be filled each time the turbo spools and will contribute to a certain amount of lag while in the time it takes to fill it. You want an intercooler that is just large enough to cool the volume of air that you will need to maintain pressure and no more. Most importantly, you need an intercooler that will fit where you want to install it. If it won’t fit, it doesn’t matter how good it is.
  2. Thermal Performance – This is where the rubber meets the road with regard to the effectiveness of the intercooler. High thermal performance intercoolers contain many tight passages that allows the air to come in contact with as much of the cooling surface as possible. The tradeoff to high thermal performance is a reduction in flow performance. While high thermal performance is desirable, so is getting the air into the intake manifold where it can be used.
  3. Flow Performance – Flow performance is measured in cubic feet per minute (CFM) which is a measure of how quickly and what volume of air passes through the intercooler. Ideally you want an intercooler that has high flow performance and a low pressure drop from intake to exit, but this parameter must be balanced with the thermal performance to ensure that hot air is not being passed through the intercooler to the intake manifold. The flow performance should match the flow potential of the turbo you have installed.

That’s all fine and good, but I suck at math… is there a simple performance metric that can be used to match my intercooler requirement to the proper intercooler? The short answer to this question is: Yes. Most quality intercoolers have a HP rating that you can use to match to your car. For instance the Garrett intercooler core that fits the Genesis Coupe is rated for a maximum of 500HP. This is a very simplified rating system for intercoolers and does not speak directly to thermal or flow performance; rather it simply says that the intercooler will handle flow up to CFM flow rates that are required for the engine to produce 500 HP without restrictions.

The simple way to decide which intercooler to choose is to stick with intercoolers the vast majority of owners are using. Do not assume that if a vendor here sells an intercooler that it will meet your performance needs; rather, seek out members who have a build similar to what you want and check their garage or look over their signatures to see what intercooler core they are using.

What are the advantages of a throttle body spacer?

A throttle body spacer’s main purpose in life is to accelerate the airflow into the intake manifold that in turn aids in better atomization of fuel contributing to a more complete burn in the cylinder. Additionally, the throttle body spacer adds a small amount of volume to the total plenum capacity of the intake manifold that can provide a little more reserve air capacity in high horsepower applications in naturally aspirated engines.

Does it work? On older engine designs throttle body spacers provided a measurable increase in HP and torque because the throttle body worked much like a carburetor in that the fuel was mixed with the air just after the throttle body throat plate. In modern multipoint fuel injection designs it can be debated that the throttle body spacer’s benefit is negligible as the fuel is introduced just prior to entering the cylinder. On direct injected engines the benefit is almost totally negated because the fuel is injected directly into the cylinder.

With all that said, a throttle body is the perfect injection site for a water/meth injection setup. I will not be covering water/meth injection systems in this thread as it is technically not a “bolt-on” modification; rather requires custom tuning along with the hardware installation to make it work. If you want to know more about meth injection, read this thread:

Super Moderator
40,514 Posts
Discussion Starter #9 (Edited)
Bolt on Modifications (continued)

Engine Thermal Management

Thermal management is an important aspect of pulling every ounce of power out of an engine that you can get. Ideally you should be keeping the hot side hot and the cold side cool to keep your engine operating at its peak. The cool side is anything going into the engine. If you remember your high school science, you know that hot air molecules tend to be turbulent and spread apart. Hot air does not compress as well as cool air… so cool air = more air = more burn potential = bigger bang.

With that said, the intake manifold is bolted to a hot engine and some of the heat that the engine produces will transfer to the intake manifold, which in turn heats the intake air. What needs to be done to reduce the effect of engine temperature on intake temperature is to thermally isolate the intake manifold by inserting a thermal barrier between the engine and the intake manifold. With that said, the air in the intake manifold is only there for a very short period of time and the thermal transfer effect is minimal; however, for those who are looking to pull every single ounce of power out of their engines, an intake thermal barrier can certainly help.

The biggest source of heat in the engine bay is on the exhaust side of the engine bay. On the intake side you want to keep the air as cool as possible to increase compressibility of the air… on the exhaust side, you want to keep the escaping combustion gases as hot as possible all the way through your exhaust because your turbo uses the energy of those expanding gases to spin the turbine. Since the turbo cannot use energy that has escaped into your engine bay, the goal of thermal management on the exhaust side is to keep the heat in the pipes and not cool and compress before it exits.

Hyundai’s thermal management strategy on the exhaust side is to redirect the heat coming off of the exhaust manifold and hot side of the turbo to parts of the engine bay that will not melt. The small TDO4 OEM turbo gets more than enough hot air to spin its little turbine so squeezing every ounce of power out of the exhaust was not one of their biggest priorities; however, there is an additional benefit to keeping the hot side hot. Hot air moves more quickly than cold air. What this means on the exhaust side is that the heat energy helps keep the exhaust flowing through the exhaust system at a high velocity reducing back pressure and providing a scavenging effect when the engine is not in boost. Lastly, effective thermal management keeps the engine bay cool. If you have a SRI, your intake will appreciate your efforts.

If you are serious about thermal management there are a number of products available ranging from heat blankets for your turbo, thermal wrap for your pipes and manifold, to space age thermal ceramic coatings that can have a significant effect on reducing engine bay temperatures and keeping the hot stuff where it should be… inside your exhaust system. Your turbo and manifold can reach temperatures of up to 1700 degrees Fahrenheit (950 degrees Celsius) and glow cherry red during hard turbo usage. Engine bay temperatures rise very quickly and heat every component inside the bay. Effective thermal management can reduce engine bay temperatures by more than 100 degrees Fahrenheit.

Catalytic converter removal

How much of a difference will it make if I remove my catalytic converters? The answer may surprise you. Not a whole lot in a stock system. The reason for that answer is that catalytic converters have come a long way since the 1970s. Auto manufacturers have long recognized the limitations that the catalytic converter places on the ability of the car to eliminate waste gases efficiently and the corresponding impact on HP reduction and have been working diligently to improve flow while still meeting environmental regulations in the various countries that they sell cars in. The result has been that manufacturers have been somewhat successful in matching catalytic converter flow through requirements with emissions restrictions. I say somewhat successful because catalytic converters still represent the most significant flow impedance in the exhaust system and will always be a source of some back pressure due to the flow restrictions. With that said, on the stock TDO4 turbo, removing the catalytic converters will not give you a horsepower boost that will throw you in the back seat of your car when you remove them because the flow through the catalytic converters closely match the flow capabilities of the stock turbo. What you will notice by removing your catalytic converters is a quicker spool because the restriction through the catalytic converter is higher at lower pressures than at higher pressures. Other side effects to removing your cats are an increase in the release of obnoxious odors and gases (duh) and an increase in volume on your exhaust output because the catalytic converters also act as a sort of muffler.

When should I remove my catalytic converters? The answer to that question is pretty simple: when your flow potential exceeds the maximum flow rate through the cats. In simple terms, when you get a bigger turbo. While the cats are pretty well matched to the stock turbo, they are no match for a bigger turbo. Now, at this point, some may say that the exhaust side of the turbo has nothing to do with the compressor side; however, they miss one little detail... the more air you shove into the engine, the more waste gas that comes out... so yes... bigger turbo means more waste gases to evacuate. You cannot realize the full potential of a bigger turbo unless you remove the restrictions in the exhaust path.​

Note: The 2.0T has two catalytic converters, the primary cat that is attached directly to the backside of the turbo itself and connects to the exhaust down pipe, and the secondary cat which is attached between the downpipe and the midpipe of the exhaust. As the names might imply the primary cat is more aggressive and more restrictive than the secondary cat. You may notice little or no difference by replacing the secondary cat. Most of your gains will be noticed when you remove the primary cat.

Exhaust upgrades

How big of a pipe do I need? Remembering that this series of articles is targeted specifically at the turbo community (sorry NA guys, it's not that I don't love you, but the NA science is pretty straight forward), the answer to that question is, "as big a freakin' pipe as you can get under your car and still clear speed bumps". There is misinformation out there that states that a car "needs" some back pressure to operate correctly". Don't fall prey to this theory.

The origins of the backpressure myth comes from the normally aspirated world of cars where it was important to keep the exhaust FLOW rate high using a relatively narrow pipe, and what we know from the application of Bernoulli's Principle that gases moving through a pipe at a high rate of speed actually decreases pressure of the gas inside of the pipe. The trick to applying Bernoulli's Principle to exhaust systems rests in finding an ideal pipe diameter that keeps the flow rate high to scavenge exhaust gases away from the exhaust manifold... opening a pipe too much will reduce flow rates and actually increase back pressure. Some folks have incorrectly deduced that because normally aspirated engines thrive on tight exhausts that it must be because tight exhausts are a source of back pressure when the flow rate is low and some back pressure is necessary for a properly running engine. Nothing could be further from the truth and NO engine benefits from back pressure, they benefit from improved flow which lowers pressure inside of the exhaust. Turbo cars have a turbine that spins and pulls exhaust gases out of the exhaust manifold. Because turbos push exhaust gases through the exhaust, there is no need to create narrow passages to improve flow rate. The hot gas just needs to go.

The best exhaust for your turbo car is no exhaust at all (an open dump to atmosphere at the turbine exit). The problem with that is that the hot gases being spewed from the turbo would melt everything in your engine bay, so some exhaust evacuation system is necessary to redirect the hot gases somewhere they can do no harm. The next best solution is a a big straight pipe from the turbo to the exhaust exit point (turboback). This of course presents problems because the noise from the engine is amplified inside of the pipe and is spewed into the world as an eardrum busting drone. While some may like this sound, most find the sound to be unpleasant and even unbearable. The next best thing would be a high flow cat back exhaust combined with a turboback pipe that minimizes the flow restrictions while providing sound resonators that cause some of the more unpleasant noises to cancel out leaving a deeper, more tolerable, and some may argue more attractive engine sound. Lastly, an axleback exhaust is mostly to tune the exhaust tone output and does little to improve performance.

Aftermarket or custom exhaust?

While the question of a custom exhaust does not really fit the "bolt on" category, it is appropo to mention them in contrast with the aftermarket bolt on option. This is one of those odd ball situations where a custom designed and fit system is usually less expensive than a pre-designed mass produced system. The reason for this reverse logic is pretty simple, most aftermarket systems have been "tuned" to emit a certain signature exhaust tone that would be considered to be pleasant or even exciting to the majority of people. Aftermarket exhaust manufacturers spend a great deal of R&D dollars to develop an exhaust system that most people would buy. Joe's exhaust pipes and plumbing down the street may use the same material and have years of welding experience, but is probably not familiar with the concept of exhaust note tuning. So the answer to this question is pretty simple... if you want a decent exhaust tone that will turn heads for the right reason, consider the aftermarket as your source. If you don't care, neither does Joe... save the money and have Joe whip up one if his specials for you.

Turbo upgrades

So... you went out and did all the bolt on stuff you could do... got yourself a tune and you are now officially maxed out on your stock equipment... yet it still seems somehow unsatisfying knowing that there are guys on the forum who are throwing 300-400-500-and even 600+ HP to the wheels. You know the only path forward at this point is to get a bigger turbo. What to do now?

The reasonable approach to buying a new turbo is to first determine where you want to be. If you are not interested in tearing into the engine to replace rods, pistons, cams, and other assorted pieces parts, the decision is much easier because you do not really want to exceed 300 ft/lbs wheel torque. Now, you might be wondering why I mention wheel torque and not horsepower, and the answer is quite simple: torque kills engines. Horsepower is a measure of work over time and is a calculated figure... torque on the other hand is a direct measurement of force that is applied to spin a wheels. It is possible to tune an engine to achieve high horsepower figures without exceeding the torque limitations of the engine if the torque is applied in a very smooth and even way. Ever hear the old saying, "Horsepower is how fast you hit the wall. Torque is how far you move that wall"? While somewhat misleading, it is still true. Torque is the force that is needed to get the wheels moving. Horsepower is a measure of how well that torque is applied in accelerating the engine/car to its top speed.

There are a number of vendors that offer bolt-on turbo upgrade kits that are designed specifically for your Genesis Coupe and have been tested and proven safe at the power levels that they were designed to work at. Always.... did you read that? ALWAYS follow the vendor's recommendations with regard to minimum required bolt-on modifications, additional equipment (i.e. manual boost controllers), and fuel requirements for their kit. The day you assume that you know more than your tuner may be the day before you are looking for an engine replacement. Use only reputable and proven tuners on this platform. While Raul's Evo n Stuffs tuning emporium may have extensive experience tuning Evos, there is a good bet that he will blow our car up because he does not know what he is doing with the Theta II engine that is NOT like the Evo motor no matter what he is telling you.

If you are intent on building your engine, then the question is how much do you plan on getting out of your build? This question will drive all of choices from that point forward to include what kind of turbo you should have. If you have gotten yourself to the point where you are considering a custom build, there is probably nothing in this thread that you didn't already know.

Note: 300 ft/lbs wtq is a derived number. You may know someone or several someones who have tuned their car for more than 300 ft/lbs of wtq, and that is great. Keep in mind that as good as your car is and regardless of how much you may love it, this is a budget sports car with budget pieces parts and budget quality. One thing that is most consistent with the Hyundai Theta II motor is that there is no consistency. 300 is an average number that has been derived by yours truly based on the "safe" tune specification of the average available "Stage III" tuning kit available on the market. Your mileage may vary.

Super Moderator
40,514 Posts
Discussion Starter #10 (Edited)
Aesthetic Modifications (Looks)

Okay... you got a fast car... but does it look badass? I can remember the first time I saw a modified lowered Genesis Coupe on wide wheels... I just about crapped myself thinking about the fact that I had the same car and could potentially make mine look as badass as the one I saw. I fell in love with the Genesis Coupe the first time it snapped my neck back in 2009 when I was passing a Hyundai dealership where I lived. It took me about 2 years before I finally came acrossed a deal that would bring me into this community and stir the mod bug in me again that had died when I got married and had kids. While some kids may dream of owning a Corvette, a Mustang, or a Camaro... I spent most of my childhood dreaming about building the ultimate machine that was one of a kind. I finally had my chance!

Right off the showroom floor the Genesis Coupe has a look and a stance that sets it apart from any other car on the road. It was one of Hyundai's first takes on its new "Fluidic Sculpture" design language and the lines very much translate to scenes of fluid in nature. I had no clue at the time what aftermarket accessories were available that would serve to enhance Hyundai's base design and create a machine that is often mistaken for much higher end cars such as the Bentley or the Jaguar. It is truly a work of art.

Well.. enough of my gushing. The purpose of this thread is to discuss the aesthetic side of modification that truly makes your machine your own. For the purposes of this discussion, paint, vinyl, and plasti-dip are not really modifications of the base look other than to change the color of something. Also not discussed in this thread are entertainment system modifications since radios are something you can buy at Wal-Mart for any car. What this thread will discuss are aesthetic modifications that are specifically target for the Genesis Coupe community. This includes body kits, diffusers, lips, spoilers, skirts, electronic enhancements, lighting, and so forth. I am sure as I am developing the content of this thread more will come to me and I will include it accordingly. So sit back, put on your seatbelts, and pour yourself a tall cool one cuz we going for a ride!

Body Kits

I've said this before, and I'll say this again... This ain't no Honda, yo! Body kits are a trade off. If you purchased the car because you loved the body, why would you want to hide it under a body kit? That is like taking a fine man/woman (your individual preference may vary) and throwing a big bag over them to hide it. Instead of applying entire body kits to your Genesis Coupe, maybe what you should be doing is figuring out specifically what you don't like and addressing those issues instead. Making the decision to install a body kit should not be made when you are under the influence of anything (several people have tattoos that they regret under the same circumstances) and it should be noted here that the cost of the body kit is not going to be the most expensive part of it. The installation of a body kit can often cost up to 3 times as much as the cost of the part you are putting on. Additionally, if you have no body working experience, never mixed bondo or fiberglass resin in your life, haven't painted anything that didn't require the liberal use of a rattle can, a body kit is probably not something you want to try to install yourself. There is no such thing as a body kit that fits perfectly out of the box. If your car has been removed from it's jig on the assembly line, there is a pretty good chance that the frame has gone through some of its own modifications along the way. Every body kit will require some "tweaking" to get it to fit. This tweaking may involve modifying stock body parts to allow the new body parts to fit. Think carefully before you start cutting away.

The Honda part of my statement relates back to all of the Hondas out there where the kid who bought this really cool body part from a guy who got it from a guy who found it laying in the junkyard somewhere.... threw the kit on himself using tie wraps and lots of glue... and then couldn't afford to get a proper paint job on it and either left it with the raw gel coat showing or got a rattle can and color matched it to his car. The difference between you and the kid with a Honda is probably at least $20,000 and you will no doubt receive the full ration of crap from other members who drive the same car as you that your car looks like crap. Remember... you didn't just buy a car, you are representing a community of proud owners. Just say no to bad body kits.

What's the deal with Carbon Fiber (and other composite questions)?

By weight, carbon fiber is stronger than steel. Manufacturers have been using carbon fiber in body parts to lighten cars while still maintaining strength and rigidity of the components they replaced. These days it seems that Carbon Fiber is less about performance and more about status. Carbon fiber parts are more expensive than their fiberglass counterparts, and as with all things more expensive, is a way for people to show how much they have invested in their build. It is an outward indicator that the builder has only invested in the very best! And... it's pretty too.

Carbon fiber (CF) and fiberglass, often referred to as a group as composites, are often the part of choice of many modders because many of the shapes that can be made with composites would be much more difficult and in some cases impossible to duplicate in metal without a significant investment of time and money. From a mass production standpoint composites are much easier to make in large numbers with far less resources than a corresponding metal part, and in most cases with fewer defects. Plus... BONUS... if it's good enough for race cars... it's good enough for the Genesis Coupe!

With all that said, you get what you pay for. There are low end and high end composite body parts available on the open market with a wide price range. If all you are doing is looking at pictures, you may find that you cannot tell the difference between the low end product and the high end product because the manufacturer of the low end product doesn't want to show you why his/her product costs significantly less than his/her competitor's product. Not only are there differences in quality, there are also significant differences in manufacturing techniques and materials that could have an impact on your wallet on down the road. Before you buy a composite body part replacement, do your research! Do not rely on the manufacturer's ad to tell you what is wrong with the product. Usually if it's cheap, it's because the manufacturer is using sub-grade materials or has shortcutted the manufacturing process to "streamline" production.

Plastic? We don't want no steekin' plastic... or do we?

One of the top complaints that I hear about automotive manufacturing techniques is about the use of plastic. More specifically polyurethane. While it may seem cheap, polyurethane parts have a distinct advantage over composite or metal parts and that is their ability to "remember" what they were made to be. Once a polyurethane part has been molded it retains a "memory" as to its shape. Twist it, poke it, dent it... in most cases the application of mild heat will remind it what it is supposed to look like and it will go back to its original shape. Polyurethane is extremely durable and flexible and can take a lot of damage before it breaks which makes it a perfect material to make things that are going to take a lot of abuse by its nature.

For instance, let's take the lip kit as an example. A lip hangs on the bottom of the front of the bumper. In addition to picking up road debris being thrown at it at highway speeds, it occasionally meets up with a curb, a parking island, speed bumps, and the odd rabbit and armadillo laying in the road that would absolutely destroy a composite or metal part. In most cases the polyurethane part will take the abuse with little or no visible damage (this is not accounting for the paint that covers the plastic which can be damaged very easily). If you get into a situation where the plastic gets dented or misshapen, heat can be your friend and can often repair the damage without much drama.

The one downside to polyurethane parts is that paint does not like to stick to it and can come off in sheets if the surface is not properly prepared. If you do not know how to prepare polyurethane for paint, this thread is not going to help you any. You can search for threads that other members have created that discuss such things or you can just take the part to a paint shop and have them do (and guarantee) the work.

The amazing flying hood and the broken windshield

Come one, come all and witness a composite hood flying up at 70 mph breaking the windshield and scaring the crap out of the driver who lived to tell about it (or not). Fun for the whole family (or not)! Have you noticed that a lot of guys who have installed composite hoods on their cars have also installed auxiliary hood latches as well? Believe it or not, the extra latches (hood pins, locks, and latches) are not just there for aesthetic reasons and actually serve a purpose. The OEM hood and all of the available aftermarket replacements use the OEM hood latch that hooks to a metal loop on the hood. On the OEM hood, this metal loop is screwed right into the hood and the hood itself weighs about 43 lbs. An equivalent carbon fiber hood has a metal loop glued to the center of the hood and weighs about 19 lbs. Now remember that there is a tremendous amount of air being sucked in through the front of the car and run through your intercooler and radiator. That air creates a positive pressure under your hood whenever the car is moving forward. The sheer weight of the OEM hood is almost enough to keep the hood in place and there is a lot of lifting force being applied to the hood latch. The very same forces are being applied to the inside of any replacement hood that you choose to go with... only the hood is much lighter and not able to press down as much against the pressure which means much more lifting force is being applied to the little metal loop that is glued to the hood.

Do you need auxiliary hood latches? Now that all depends on your ability to be able to drive with a hood sitting on your windshield at high speed. If you do not feel confident that you can successfully execute this maneuver and live to tell about it, then most certainly auxiliary latches are for you. Now, you will talk to members and vendors who will tell you that hood latches are more for decorative reasons than actually serving a purpose. They will tell you that they have been driving with their composite hood for umpteen zillion years and have never had a latch failure. While this may be true, take the time to Google "Hood Latch Failure" and make a judgement call. A good set of hood latches will cost less than $100 and could save you from having to change your underwear or worse. Think about it.

Spoilers, wings, skirts, lips, and diffusers, oh my!

When performance is of the utmost, the one thing that you need to start thinking about managing is the airflow around, under, and over the car. The primary purpose of aerodynamic enhancements is to change how the air affects how your car handles at speed. The faster you go, the more the air will impact handling and performance. The other reason to install aerodynamic enhancements is because they look cool. There is nothing wrong with doing this, but you will gain a lot more legitimacy in conversations with other car enthusiasts if you can explain what your aerodynamic accouchements do.

Spoilers (Warning: Spoiler Alert!)

As the name might imply, spoilers are designed to spoil the air moving around the car. Contrary to some popular beliefs, spoilers are not designed to provide any downforce on the car. The purpose of a spoiler is to reduce parasitic drag and the low pressure zone behind the car caused by turbulent air.


I may have let loose on the video above a little too soon because it also explains the function of an automotive aerodynamic wings fairly completely. However, what was not really discussed was why a wing is important to aerodynamic function. While a wing will do what it was intended to do at any forward speed - increase down force - what was not really discussed was when a wing would be necessary. The downforce of the wing is designed to counteract the lifting force experienced at high speeds. A sports car is shaped a lot like a wing. It has a rounded top and a flat bottom. Just like a wing, a car will experience aerodynamic lift as it goes faster. If you are not driving fast enough to create aerodynamic lift, you probably don't need a wing.

Rear diffusers

Unlike spoilers, the name of the diffuser does not really elude to what diffusers really do. The purpose of a rear diffuser is to increase the downforce on the car. The way that it does this is by accelerating the speed of the air traveling underneath the air thereby creating a low pressure area underneath the car. Before we go on with the detailed explanation as to how a diffuser works, I would like to point out that 99% of the rear diffusers offered by aftermarket vendors are purely cosmetic in nature and contribute nothing to downforce. In fact, there is only one rear diffuser available to purchase that can remotely be considered functional.

Front lips and side skirts

A front lip serves as an air dam that aids in providing moderate downforce to the front of the car by limiting the amount of air that is allowed to move under the car. A splitter lip serves essentially the same function as a full lip but works more like a front wing. If the splitter is combined with front canard wings, the effect is multiplied exponentially.

Functional side skirts reduce the ground clearance of the sides of the car to continue what the front lip has started. In other words, side skirts make little sense if no front lip is installed and a front lip is not nearly as effective if side skirts are not installed since they both work together to keep air from flowing back under the car. The other thing that a functional front lip and the side skirts do on a Genesis Coupe is reduce the "parachute effect" of the rear bumper. If you take a look at the backside of the rear bumper, you will notice that the area is hollow. A certain amount of air that travels underneath the car will get trapped in this hollow area and create drag.


Super Moderator
40,514 Posts
Discussion Starter #11 (Edited)
Aesthetic Modifications (Looks) (continued)

Lights and lighting

:shock:Science Alert:shock:​
The following content contains science. It sucks, but if you want a thoughtful explanation as to why some lights are better than others and you want that discussion to include something other than, "o_O look... pretty lights", the science stuff is necessary. You have been duly warned.
Disclaimer: The author nor is responsible if your head spontaneously ignites.​

Okay, before we get started on the discussion of lights, let's be clear that we will not be discussing the Fast and Furious kinds of lighting that is available on eBay... so don't ask. If you want to install underbody lighting, wheel well lighting, behind the grill lighting and various LED odds and end lighting on your car, go for it but don't tell me about it. I don't want to know.

With a that said, the type of lighting that I will cover involves modifications to the stock lighting and aftermarket lighting options to replace the stock lighting. Additionally, I will cover some aftermarket lighting additions that can make life a little more convenient while simultaneously looking kind of cool.

My headlights suck!

Unless you have OEM HID headlights, your stock halogen headlights really do suck. If you have had high intensity discharge (HID) xenon lighting before, all halogen lights suck. With that said, HID upgrades are some of the most popular upgrades that are done on the Genesis Coupe; however, most are done without a good understanding of how to keep from blinding other drivers in the process.

Nothing sucks more than being on a two lane road and the approaching car has poorly aimed HIDs that are blinding the crap out of you as you get closer. There are several things that you can do to keep from being "that guy".

Why is the sky blue?

To understand why certain HID colors don't seem to provide as much light output as other colors you need to understand how colors react in the atmosphere due to their wavelength. The reason why the sky is blue during the day is that blue light, more than any other color in the visible spectrum is more prone to atmospheric scattering. As a result, the sky appears blue because the air is being lit by blue light that is being refracted out of the white light that is passing through it due to blue light's extremely short wavelength.

Why does it seem like blue lights don't illuminate as bright as white light?

Answer: Because the sky is blue (didja see what I just did there?). The image that your eyes see depends greatly upon the light that must bounce off of the subject and reach your eye. Everything you see is essentially a reflection of the object you are looking at. So, if you have blue tinted headlights, much of the light output of your lights are scattering in the atmosphere before it even reaches your subject and then the reflected light is being scattered even more on the return. The result is less visible light is actually reaching your eyes.

What is worse about blue light is that all this atmospheric scattering actually makes the light appear brighter to a third person observer. This is why police cars typically use blue lights for their emergency lighting. Due to atmospheric scattering, blue lights are almost impossible to ignore because they seem to light up the entire area around the police car. To an oncoming driver, bright blue HIDs are almost blinding... even if the light is not pointed directly at you.

So... what is the best color temperature for lighting?

Answer: If you want to see, you will want lighting that is as close to daylight color temperatures as possible. Your eyes see best in daylight. Considering that we are not naturally nocturnal animals, this makes sense. Natural daylight color is in the 4300 Kelvin color range, so it follows suit that lights that emit the bulk of their emissions in the 4300K range will result in better illumination than any other color temperature. Blue occurs in the 5-8000K range. With that said, from 5000-6000K blue is not the primary color and is less noticeable than in higher color temperature ranges. If you want a little blue in your light to say, "Hey... I've got HIDs" but you do not necessarily want to blind other drivers and you would actually like to see where you are going, do not purchase lights above 6000K.​

Taste the rainbow!

You probably have noticed that some folks have a very sharp cutoff line on their HIDs and the top edge of the light has a some rainbow colors and you are probably wondering how they did that. The answer to that question is that your halogen headlights were not designed to use xenon bulbs. The light emitted from xenon bulbs comes out in a different pattern and the reflector bowl is not really shaped optimally to reflect xenon produced light. Additionally, Hyundai has chosen to use a Fresnel type lens instead of a clear lens to help diffuse and soften the light output from the projectors. In other words, the light cut off is not as sharp as it could be.

^^How do I fix that?^^

The ideal fix is to replace the halogen projector lamp with a projector lamp that was specifically designed for xenon lighting. Although this modification can be done without the need for exotic special tools or equipment and can actually be done in your kitchen it is not for the faint of heart. There are several DIYs on the forum that describe how to take your headlights apart if you are interested in doing it yourself; however, you may choose to use one of our very competent vendors to do the work for you.

If you are brave enough to open the headlights but not brave enough to take a Dremel tool to it to modify the lights for new projectors, option B is to just replace the Fresnel lens with a clear lens. None of our vendors here on GenCoupe sells the clear lens kit for our projectors separately. For that you will have to do a Google search for "2.5" Black series clear lenses" The first search hit should be what you are looking for. These lenses are completely plug and play bolt on replacements for the stock lenses. Installing these lenses will not fix all of the problems with the halogen projector, but it will sharpen up the cut off line and give you some of that rainbow you are looking for.

A couple of words about installing HIDs in your factory fogs:

You suck.

The factory bowl reflector in the fogs combined with HIDs will produce a blinding light that will trash other driver's night vision and could potentially cause you to have a head on collision with that blinded driver. Unlike with your projectors where the light is shaped in part by the bowl and in part by the lens, the factory fogs rely entirely on the bowl. The purpose of fog lights is to illuminate the sides of the road because normal driving lights cannot penetrate the fog and do a poor job of illuminating the sides of the road. HIDs installed in the factory fogs defeat the purpose of the fog lights, create a stupid amount of glare for other drivers (and you, if you are in the fog), and are just generally dangerous. Don't suck... don't install HIDs in our fogs. If you are worried about color matching the color temperature of your headlights in your fogs and you don't necessarily ever use your fogs for lighting, consider replacing the halogen bulb with an LED.

LEDs, LEDs, LEDs Everywhere!

The latest rage in the automotive lighting circuit are Light Emitting Diodes or LEDs. To be clear, LEDs have been around for a very long time; however, until recent years have not been bright enough to be practical for anything more than lighting indicators. So, what has changed? In recent years there has been a huge push by governments to encourage the development of energy efficient lighting that has prompted researchers to look at ways to replace the less efficient lighting systems that are currently available and dominate the market. The most prolific of these systems are the incandescent lights that are found just about everywhere. The concept of the incandescent light is simple... run electricity through a high resistance wire in a gas filled environment and the filament heats up and emits light. Although much light is emitted by incandescent light, they consume a great deal of power and much of that energy is converted to heat instead of light. The advantages of LEDs are numerous. They are small, consume much less power than their incandescent counterparts, are very tough and durable, typically have a very long life, stay relatively cool during operation, and can be lit in a variety of colors without the need of color filters. Although in automotive lighting applications the power that lighting consumes is not significant (you won't save gas by using LEDs), the long life, toughness, ability to quickly switch on to full brightness almost instantaneously, and the ability to emit light of different colors makes them ideal for automotive applications. Oh, and lets not forget to mention that they are pretty cool because you can arrange LEDs any way that you want to create very unique and customized lighting fixtures.

As with most things in the aftermarket world, not all LEDs are created alike. You have your name brands, you have your generics, and you have your cheap knockoffs. The brightest LEDs on the market right now are surface mount diodes (SMDs) made by Cree. SMDs are typically brighter than other LEDs because a lot of individual LEDs can be mounted to a single circuit board. The light can be further amplified and directed by using reflectors and lenses that will concentrate the light in a specific direction. Because of these enhancements it is often impossible to determine how much light a given LED will output simply by looking at how much power they consume as we would with a typical incandescent bulb.

How do I compare the light output and quality of different LED bulbs?

That is an extremely good question because the quality of light output is much more than simply knowing how much light is output. The question of quality really comes down to how much of the light that emitted from the bulb reaches the eye, not how bright it is. You often cannot do an apples to apples comparison between the quality of an incandescent light source and the quality of an LED light source because the color temperature of the lights are different. Typically a "white" incandescent light bulb will emit light that is lower in the Kelvin temperature range: typically between 2700K and 3300K which makes the light appear yellowish. Typical "white" LEDs emit their light in the 5000K range, or more specifically, much closer to the color of daylight that our eyes are more efficient at working in. In other words, white LEDs work in a color range that your eyes do not strain in, so the quality of the light emitted by white LEDs is "better". So, the answer to your question of how do you compare the difference between different LEDs is that you must not only know the light output in Lumens but you also need to know the color temperature of the light. The brighter and the closer the light is to 4300K (the ideal color temperature of pure white light), the better the quality of the light output. If the vendor does not list the lumen output or color temperature on their site, ask them. If they don't know, then chances are they are knock offs of unknown quality. You can buy them, but don't complain if they turn out to be complete crap.

Vendors here are rip offs! I can go on eBay and get the same or better LEDs for a fraction of the price!

If you believe this statement, then you should certainly purchase your LEDs through eBay. LED sellers are typically based out of China and the LEDs are assembled in factories where 5 billion chinese working for 5 cents a day make everything from chop sticks to ultra high definition flat panel televisions. When your money goes to China, the chinese use it to buy American property so that one day you will get to work in a big factory for 5 cents a day. Most of you folks really don't understand the long term consequences of what you do.

Seriously though, our vendors support our community. Some have been with this platform from the very beginning. They search tirelessly through the internet to find high quality, cool stuff that we can put on our cars. They participate in our events. They give us stickers that improve our HP output. They support the customer long after the sale. Sometimes, they cost more. When you purchase a product from one of the vendors who support this community, you are providing an incentive for these vendors to continue to support us, find, develop, and customize more new cool things in the future. Nobody is in the business to lose money, and most of our vendors cannot compete head to head, dollar for dollar against 5 billion chinese working for a pittance of what we would call a salary. So, yeah... you can do your own work and you can buy things from other vendors (including eBay), but when things go wrong, and yeah.. when you are experimenting sometimes things do go wrong... don't be at all surprised if the vendor that you made the purchase from is long gone and won't respond to your emails. They really don't care about you or what you think their reputation ought to be. At the end of the day, you may find that working with our sponsored vendors is not quite as expensive in the long term as you thought.

What lights can I replace with LEDs?

Answer: All of them... although you may not want to replace all of your lights with LEDs just yet. For signal indicators, interior lighting, and backup lighting... LEDs work just fine. The light output of high intensity LEDs are brighter than their incandescent counterparts; however, if you think that you can replace a Halogen bulb with an LED and get the same light output, you would be mistaken. LEDs has come a long way from where they were, but they're still not good enough to replace the brightest lights on your car. If you are using your lights for anything other than aesthetic reasons, i.e. to see down the road on a dark night, you probably want to stick to more traditional lighting methods for the time being.

Super Moderator
40,514 Posts
Discussion Starter #12 (Edited)
Aesthetic Modifications (Looks) (continued)

Angel Eyes, Demon Eyes, and DRLs...

In 2001, BMW introduce a new concept in automotive lighting adding two coronal light rings around the headlight projector that were used to replace the the half lit high beam DRL that was on previous BMW 5 series cars. While they were quite dim the idea was considered to be revolutionary and that led to a number of aftermarket manufacturers to develop Halo or "Angel Eye" lights, as the have been come to be known, for other cars that had similar projector lights as the BMW. Today's choices are quite impressive with different manufacturers using different techniques to duplicate BMWs successful idea. The original Angel Eyes were lit using cold cathode fluorescent lights (CCFLs), had a dingy yellow tinge to them, and the installation wasn't exactly straight forward. Today's available options use SMDs mounted on a round circuit board and only require the installer to connect a red and black wire to a 12V power source without the need of complicated starters, converters, and what not. Some designs use glass light rings where the light is infused into the tube at an opening on one end and beamed around the glass to duplicate BMWs design more closely. Other designs still have full RGB LEDs, enabling the user to change the color of the LED ring using a remote control from inside of the car. Regardless of what type of Angel Eye you decide that you want to install, you are going to have to disassemble your headlight to install them and you need some basic wiring knowledge to properly hook them up. The vendors on this forum who specialize in lighting also carry LED halo lights that will fit the projectors on the Genesis Coupe. If you choose to use another vendor, the light projector is 80mm in diameter.

OEM Headlights modified with painted bezels, 4300K HIDs, switchback LEDs on turn signals, and RGB Angel Eyes

Where Angel Eye's are halos that light around the projector, Demon Eyes add color in the projector bowl that glow through the projector lens. There are passive and active methods for adding color. A passive method of adding color is to disassemble the projector and to paint the shield the color that you want to the lens to pick up. The passive method requires outside light that comes in through the projector lense to reflect off of the projector shield and as a result is very subtle.

Anatomy of a Typical Headlight Projector

An active method of adding color is to install colored LEDs inside of the projector bowl that light the inside of the projector bowl and is much more prominent when the headlights are off.

Blue Angel Eyes with Active Red LED Demon Eyes

Note: In every state in the United States, displaying Red or Blue lights while operating a motor vehicle on public roads is illegal. Some states ban all colors other than white and amber. While white Angel/Demon Eyes are perfectly legal in all 50 states, colors are not and should only be used for show purposes only.

DRLs or Daytime Running Lights actually started out as a gimmick in the early 1960s. Greyhound bus lines public relations started this gimmick to promote its "safety image." There was a 24% reduction in bus accidents and the conclusion was made that the daytime headlight use must be the reason. It would not be until 1995 that GM would start installing DRLs on select models after the National Highway Transportation Administration (NHTSA) finalized a rule that would allow full time DRLs to be installed on cars in the United States. It would be another two years before GM made DRLs standard equipment on their entire fleet. Many other manufacturers followed suit. There have been a number of studies conducted that suggest that there is a measurable (although not significant) reduction of collisions involving cars with DRLs installed. Although the NHTSA allows the installation and use of DRLs, they are not mandatory in the United States; however, our neighbors to the north have mandated that all cars made or imported after January 1, 1990 are required to have DRLs.

The 2010-12 US Spec Genesis Coupe in all trim levels have no OEM DRL option. Top model (Track and Ultimate) Genesis Coupes made in 2013 and forward have OEM DRLs installed as part of the fog light assembly. The fog light assembly in the 2013+ Genesis Coupes are not backwards compatible with previous models, so the only DRLs available to older models are aftermarket options. Installing functional DRLs can reduce your insurance premium. Check with your insurance company to see if a discount is available. Some insurance companies will not offer a discount for non-OEM installed DRLs.

Vendor light retrofits

What literally started as a hobby for some of our more talented members have turned into lucrative businesses. To date there are three vendors that do custom light retrofits on all model year Genesis Coupe headlights and tail lights. As with other types of businesses with such a focused market segment, the number of vendors offering retrofit services is limited to the number of folks who are willing to pay for these retrofits. They are not cheap. As a matter of fact, from a cost perspective, most aftermarket headlight systems available for the 2010-12 Genesis Coupes (sorry '13 and '14s... nothing for you yet) are less expensive than a retrofit. With that said, a properly modded retrofitted headlight is a work of art and usually unique to each owner as options are customized for each order. If you have money burning a hole in your pocket and do not have a mind to open your headlights (or take a Dremel tool to cut open your tail lights) a custom retrofit may be just the thing for you. Keep in mind that none of the vendors keep a stock of lights sitting around waiting to be retrofitted which means that you will have to send them a set of lights and your wait time can be anywhere from weeks to months depending on that vendor's workload. Headlight retrofits are labor intensive jobs and take time.

Aftermarket options

Again, sorry Gen II Genesis Coupes... your time will come, but not now. The only aftermarket options for headlights are only available for the 2010-12 Coupes. Fortunately, all model year tail lights are interchangeable so there are late model GenCoupe options for tail lights. Check out our vendor websites to see what is available. Additionally, there are a few choices for aftermarket options that are only available on eBay from Korean-based vendors. Keep in mind that regardless of what after market option you choose, non-OEM lights will not be of the same quality or build as the OEMs you are replacing. For every aftermarket light option you will find owners who have had problems with their aftermarket purchases. Unfortunately, to date, there are no better options available.

Spyder Black Bezel headlights with LED DRLs and Refracted Glass LED Angel Eyes

Spyder Black Tail Lights with 50% Lamin-X tint.

If you look at the license plate frame, you will notice that there are 6 high power (60W) Cree LEDs that light when the car is put in reverse to supplement the 10W Cree backup LEDs in the tail light housing.

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Discussion Starter #13 (Edited)
Aesthetic Modifications (Looks) (continued)

Electronic add-ons that will amaze and amuse your friends (and potentially save your butt)

Here's where things get really interesting. There are a couple of electronic modifications that can be done for relatively low cost considering the return on investment that you will get. The two mods are installing an Android tablet and installing a dash cam. The tablet modification can be done on any trim level 2010-12 Genesis Coupe. There is currently no plug and play ready mounting option for the new model Genesis Coupes; however, the modification can be adapted to Android-based smart phones. The dashcam mod can be done on any car.

Why install a tablet in my car?

Serious? If you have to ask, there is no reason to install a tablet in your car! A tablet can act as a total information system for your car. You can connect the tablet to your on-board diagnostic system (OBDII) to display and log everything the car's electronic control unit reports in near real time or review and clear check engine codes/lights. Your tablet can be a real time GPS. Your tablet can provide traffic information. Your tablet can provide localized weather reports. Your tablet can keep you connected to the world. Your tablet can be an entertainment system. Your tablet can control GoPro cameras that are attached to your car. Your tablet can connect you to your internet enabled home security system. You can connect a first person view (FPV) camera attached to a quadcopter controlled by your passenger who is flying the quadcopter chase on your car going down the road capturing video. (You did notice the word Geek in my screen name, right?) In other words, what you can do with a tablet in your car is limited only to your imagination. If you have no imagination, then.... yah... you don't need a tablet.

What do I need to install a tablet in my car?

There are two types of kits available for the 2010-12 Genesis Coupe. The Type A bezel kit and the sleeker Type B bezel kit. The Type B kit is generally more expensive than the Type A and some members have reported an issue with the GPS signal being blocked by the metal retention strap on the Type B. You will need to make sure that you get the kit with a relocator kit if you want to keep your blue screen. (If you have an aftermarket radio and you are not using the blue screen, you can just remove it). You will need a 12V power supply for the tablet. Additionally, if you intend to connect the tablet to the auxiliary in port of your radio, you will need a double ended mini stereo connection wire long enough to reach the jack from your tablet. If you are using the Type B bezel, the metal retaining strap may block the GPS signal to the tablet. A member on the forum sells plexiglass mounts or you can make your own (just don't make it out of metal). Lastly, you will need double-stick tape if you are installing a Type A bezel. The Type A bezel has a surround that sticks to the face of your tablet to keep it in place.

What kind of tablet should I get?

Any 7" Android tablet will work. You can also use an iPad mini or the Microsoft Surface; however, you may find that all of the applications discussed on this forum is only available on the Android. That is not to say that there are not iPad/Microsoft equivalents, just that the Android has been around for a lot longer in a 7" or 8" format and is generally much less expensive than the iPad or Surface. This thread will focus on the Android because that is the tablet of choice by most members.

With all that said, don't go too cheap on your tablet purchase. As with everything else, you often get what you pay for. The ideal tablet has on board GPS, Bluetooth, Wi-Fi, a long battery life, and is either loaded with or can be updated to a version of Android that is compatible with all of the applications you intend to use. The two most popular tablets installed are the Acer A100 and Google's Nexus 7, both of which meet or exceed the performance and equipment requirements for any application you wish to run. Samsung's Galaxy Tab is also a popular choice.

Acer 100 installed in a Type A Bezel

How do I connect my tablet to my car's on board diagnostic system?

In order to connect your tablet to your OBDII port, you will need an OBDII module. They come in two flavors, Bluetooth and Wi-Fi... either will work as well as the other. If you also use your tablet to play music and you connect your tablet to the car's stereo system via Bluetooth, you may want to get a Wi-Fi module. If you use a Wi-Fi hotspot to connect your car to the internet, you may want to choose the Bluetooth module and if you still want to play music from the tablet use a hard wire from the tablet to the auxiliary in connector for the stereo. There are several OBDII modules made ranging in price from $15.00 for an ELM 327 module to more advance modules that will run upwards to $150.00. The biggest difference between the low end and high end modules is data throughput. The higher and faster the throughput the less latency your tablet will display. Look at the different models and make a determination as to which one best suits your needs.

One recommendation that I would make is that if you intend to connect an OBDII module to your car that you also purchase an OBDII extension cable that has a 90 degree connector on the end that connects to the OBDII plug on your car. The reason for this is simple: you don't want a big black module with flashing lights hanging down underneath your dash. Not only will it get in the way, the flashing lights at night will be a huge distraction. Using the extension cable will enable you to place the module anywhere under the dash where it will not be in the way.

What applications should I have on my tablet?

This is a loaded question because it would depend on what you intend to use the tablet for. Typical installations will include the following applications:

  • Torque or Dash Command - Display your ECU data and view/clear check engine light (CEL) codes. (Requires an OBDII Bluetooth or Wi-Fi module)
  • Automateit or Tasker - A macro task manager. Allows automatic initiation of macros that do everything from putting your tablet to sleep to opening and closing applications. Note: Some functions are only available on a rooted tablet (more on rooting later).
  • A weather application - Realtime weather updates while on the road (internet connection required)
  • Waze or Inrix - A social media mapping application with member generated traffic and hazard updates. (internet connection required)
  • Sygic - An offline 3D navigation application. Works just like your dedicated GPS system (no internet connection required for use) Uses the same maps as TomTom.
  • WiFi File Transfer - Allows remote Wi-Fi connection of your tablet to a PC on the same Wi-Fi network for file transfer and backup.

Torque screenshot

Most tablets will have media players pre-installed. If you have a favorite media player, then go ahead and install that as well. In fact, install anything you want on your tablet... it's yours.

How do I connect my tablet to the internet?

Option A: You can get 7" tablets from any of the major cellular network providers that will provide you with 24/7 internet access wherever there is data service (there is less coverage for data services than voice services). This is the most convenient option, but also tends to be the most expensive. Additionally, you may get yourself tied into a contract that you can't get out of.

Option B: Purchase a pay as you go cellular Wi-Fi hotspot. The advantage of this approach is multifold. First, you only pay for what you use; albeit most cellular data programs are more expensive per GB than their contract counterparts. This is only an issue if you are streaming big data such as video or music. In most applications (even if you occasionally stream video) you will use less than 1 GB of data in a month. Most Wi-Fi hotspots will allow up to 5 devices to connect simultaneously, which means that your passengers that have tablets or laptops can also use the hotspot to stay connected or entertained.

Option C: If your internet provider allows you to do this, use your smart phone as a Wi-Fi hotspot through tethering. Not all cellular providers allow tethering and most charge extra for this service (some do not). Check with your cellular provider to see if tethering is an option for your plan. You may find that you can get more bandwidth for less money and not be obligated to a signing contract.

Option D: Look for free internet hotspots. This one is a little more sketchy; however, there are more and more free Wi-Fi hotspots than you may think. The disadvantage is that you will only be able to use the hotspot when you are near one. There are applications available that will allow our tablet to automatically connect to any open Wi-Fi hotspot that is in range... so even if you didn't know it was there, your tablet will find it and use it. The advantage to this approach is that your tablet will automatically update whenever it is in range of an internet hotspot and the best part... it's FREE.​

If you are choosing a cellular provider - Be sure to look at the data coverage areas. A cheap plan won't help you if you cannot connect to the internet where you need to. Also, pay attention to whether the data provider is on a 3G or a 4G network. Although most of what you may use a data connection for does not necessarily require a fast connection, some do. Faster is always better. If you are using Google Maps as your navigation application, you don't want to be staring at a blank screen when you don't really know where you are going because your map cannot update fast enough.


  • Why do you need one? Because stuff happens.
  • Are dashcam videos admissible in court as evidence? Yes as long as it is time and date stamped.
  • What kind of resolution do I need? At least 720P but more is better.
  • What features should I be looking for in a dashcam? High resolution, battery backup, record on key on, auto looping, large SD Card capacity, parking mode, shock detection and auto record, night vision down to at least 1 lux (moonlight), smooth video (look for samples on YouTube), and finally low grain.
  • How hard is it to install a dashcam? In most cases you won't need much more than a pair of needle nose pliers to install one. (You may want to buy an "add a fuse" kit to tap into your fusebox for power)
  • Can I use my GoPro as a dashcam instead of going out and buying a dedicated dashcam? Yes, but the video will not have a date/time stamp and the veracity of the video can be questioned as it can be edited without obvious indicators that the video has been altered. Additionally, the GoPro needs to be powered on manually. The reason why dashcams work is because they come on automatically everytime the car is turned on. Use your GoPro for what it was intended for (as an action cam) and get a dedicated dashcam.

When it's your word against the other driver's, a dashcam can be the difference between being blamed for an accident you didn't cause and collecting big bucks from someone else's insurance to get your car fixed. Your insurance company may limit how much you can get from a claim; however, the other guy's liability insurance will always pay more.

"I'm pretty tired... I think I'll go home now."
~Forrest Gump

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Discussion Starter #14 (Edited)
AFRs Explained!

AFRs Explained

Get a wideband O2 gauge, they said... so you did. Now what? You see numbers jumping all over the place and they don't mean anything to you. What should your gauge be reading? What is normal? What is not normal? When should you be concerned? What are the indicators that tell you that your car is about to blow up? What's the point of all this?

Why get an Wideband O2 Gauge?

If you have a tune, you NEED an O2 gauge? Why? Because a tune, by its very nature, removes some of the safety factor that is built into the factory tune. Most factory forced induction cars run very rich full load mixtures, with 10:1 not being uncommon. This is done for engine and cat converter safety reasons - in case an injector becomes slightly blocked, or the intake air temperature rises to very high levels. A tune takes advantage of the fact that the manufacturer has put a stupid amount of fuel into the tune in order to ensure safe operation; however, by narrowing the safety margin, a blocked injector or a bad batch of fuel can ruin your day quickly.

So, what is a "good" AFR range?

Unfortunately, there is no real good answer to that question in simple terms on a forced induction (FI) (turbo) engine. The reason for this is pretty simple... a turbo engine is only "forced induction" when the turbo is spooled and producing positive pressure, in all other respects, an turbo engine out of boost acts just like any other naturally aspirated (NA) engine. For an NA engine (or a turbo engine that is not in boost) the stoichiometric AFR is 14.7:1. What stoichiometric means is that the combination of air and fuel (14.7 parts air to 1 part fuel) at mean sea level pressure will burn 100% of the fuel in the mixture using up all the air in the mixture. Thus, when the air part is reduced to say, 12.0:1 we say the mixture is "rich" because there is less air in the mixture. Likewise a higher first number of say, 16.8:1 is considered "lean" because there is more air in the mixture. Notice that in the formula that the fuel remains constant and the air is the variable that continues to change. For an FI engine running out of boost, the ECU targets (commands) an AFR of 14.7:1; however, atmospheric conditions such as pressure altitude and temperature will impact the actual AFR to be slightly less or slightly more than what was commanded. When you get your wideband O2 gauge, you will notice that you spend much of your time between 12.5:1 - 16.2:1 because the manufacturer is trying to balance power and safety.

Best AFR really depends on what your goals are. Power or fuel economy?

Boost changes everything!

When you are under about 80% throttle, the ECU can "see" the O2 readings and makes adjustments to the fuel flow to maintain a "safe" AFR range, even when you are in boost. This is known as closed loop fuel management. Above about 80% throttle, the ECU manages AFR using a fuel/boost/RPM table to determine how much fuel to inject and it essentially ignores the O2 readings (open loop fuel management). This is where you need your O2 Wideband gauge! As you increase throttle, the boost increases shoving more and more air into your intake manifold and your fuel injectors must pump in more fuel to compensate for the additional air.

Open Loop Logic vs. Closed Loop Logic

AFRs are more than just balancing the air and fuel for the most efficient bang for the buck. Remember I had also said that the manufacturer goes for a rich mixture to protect the engine and the catalytic converter? A rich mixture will run cooler than a lean mixture of fuel. As you increase boost, you are also increasing the operating temperature of your engine and the cooresponding exhaust that leaves your engine. Things that get too hot tend to break. On top of that, there is an airflow imbalance in the factory intake. The #4 cylinder (the one all the way in the back of the engine) gets a good deal more air than the rest of the cylinders because of the way that the intake manifold flows. As a result, the #4 cylinder runs much leaner than the #1 cylinder. What this means is that everyone has to tune to make the #4 cylinder happy (not run lean and too hot which leads to pre-detonation [knock]) which means that the rest of the cylinders have to run pig rich. As a result, the ideal target AFR in closed loop under full boost is 11.7:1; however, any value from 10:1 to 12.5:1 would be considered "safe" (most Wideband O2 gauges cannot read below an AFR of 10.0:1). The additional fuel that remains unburned in the combustion is actually used to cool the engine to prevent overheating.

When should you be concerned?

First off, if your car runs rich, there's not much you can do about that. The tune is rich, but it's usually done so as to compensate for other mods that you might accomplish after you get the tune that would impact AFRs. Any mod that changes the way air travels through your engine WILL affect your AFRs. Determining if that effect will have detrimental impacts to how your engine operates is the reason why you have a Wideband O2 gauge.

During normal cruise (closed loop) your ECU is watching your narrowband O2 range to keep it in the green. If there's a problem, your ECU should either correct it or shut you down. In open loop you would want to see AFR ratios down to at least 12.5:1 initially, and as you build full boost ideally you want to see AFRs below 11.7:1. AFRs below 11.0:1 means that you are probably fouling your plugs and making a crap load of black carbon which can cause your car to run like crap in the long term, but is not detrimental in the short term. AFRs above 12.5:1 on wide open throttle above about 5250 RPM is a danger sign... pull your foot off the throttle and figure out what your problem is before you build a window in your lower block right around the 4th cylinder.

Note: Tunes do not go bad over time. If the tune you had was in the safe AFR range at the time you got it, then something has changed with your car to make the AFRs go awry. If you are buying the cheapest gas you can find trying to save a few bucks, you may have your answer right there. Once you run out your tank of gas (run it down as far as you can) go put some good gas in it from a Tier 1 supplier (Shell, BP, Chevron, or Exxon) and see if that doesn't fix your problem. If it does not, pull your injectors and have them flow tested. If your injectors are severely clogged they may or may not be salvageable with a cleaning. Using cheap gas may cost you a set of fuel injectors. My guess is that you are going to come out behind if you do the cost-benefit analysis on how much money you saved on cheap gas and the cost of new injectors (or having them flow tested and cleaned for that matter). Moral of the story: Get off the cheap gas already... it's costing you more in repairs in the long run!

The bottom line:

If you tune, get a Wideband O2 gauge. Just because the tune is "safe" because it has been running on thousands of cars and no one has ever had a problem with the tune does not guarantee that you will also. As I said, it can be something really simple like a grain of sand blocking an injector or bad fuel that has more water than gas in it is enough to throw your AFRs into the toilet. If you find yourself in dangerous territory with regard to AFRs, you can still drive your car but do not exceed 80% throttle... do not boost more than about 5-8 PSI (what... you don't have a boost gauge? Shame!), and do figure out what the problem is.

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Discussion Starter #15 (Edited)
Turbo Basics... what's it all mean?

A turbo is nothing more than a high efficiency air pump that takes atmospheric air and then compresses it for use by the engine. All internal combustion engines produce power by converting heat (energy that is created as a result of chemical reaction that we call combustion) to mechanical energy. The two components that the engine needs to make power is fuel and an oxidizer... in this case, air. In normally aspirated (NA) engines, the engine receives air on the intake stroke by suctioning air through the intake and intake manifold into the cylinder. Ideally it will suck as much air that will fit uncompressed inside of the cylinder space. A forced induction (FI) system such as a turbo or supercharger pumps additional air into the intake and the cylinder to allow the engine to take a much bigger gulp of air than it could do on its own. The more efficient the pump, the more air that can be forced into the cylinder. The last ingredient is that while the cylinder is being pressurized, the fuel injectors must pump an adequate amount of fuel into the cylinder to sustain a consistent and controlled burn rate. Too much fuel will slow the combustion rate and will not burn completely. Too little fuel results in a rapid burn rate that cannot be controlled (detonation).

More on AFRs

The ideal mixture of air and fuel (unleaded gasoline) to ensure complete combustion is 14.7 parts air to 1 part fuel. This varies slightly depending on the composition/purity of the fuel and it's additives; however, for the purposes of this discussion 14.7:1 is the stoich value of fuel. In measuring air fuel ratios (AFRs), the fuel value is constant and the air value is the variable. So, as air is decreased in relation to the fuel, the AFR value gets smaller, i.e., 12.0:1, and the mixture is considered "rich". If the volume of air is increased in relation to the fuel, the value gets larger, i.e., 16.0:1, and the mixture is considered "lean". All things being equal, maintaining a AFR of 14.7:1 is ideal for ensuring complete combustion; however, a complete burn does not always mean that power is being produced through the entire power stroke A richer mixture slows the burn rate and results in an incomplete burn, but ensures that the burn continues through the entire power stroke. When you add forced induction into the cycle, things cease being equal and some adjustments have to made to compensate for the problems created by the additional pressure.

When air is compressed, heat is created. Heat acts as a catalyst in chemical reactions making the air/fuel mixture in the cylinder more volatile. Ideally, you want to be able to ignite the air/fuel mixture just before the piston reaches top dead center (TDC) (the highest compression point of the piston stroke) which will yield the longest power stroke (created when the combustive mixture ignites and expands pushing the piston down to the end of its full stroke or bottom dead center (BDC)). When the air fuel mixture is compressed, it heats up and the possibility exists that it can get so hot that the air/fuel mixture ignites prior to full compression resulting in on uncontrolled burn or what is most commonly referred to as an engine knock. The reason this is bad is because the piston is still moving to compress the air/fuel mixture as the violently expanding gas is trying to force the piston down. This is where bent/broken rods and pistons and damaged valves come from. To alleviate some of this problem, additional fuel is added to the air/fuel mixture to aid in keeping the mixture cool and slowing the combustion rate so that it does not pre-detonate in the cylinder prior to full compression. You do not get more power from the additional fuel being added because there is not enough air to oxidize all of the fuel which means that the unburnt waste fuel is dumped out of the cylinder on the exhaust stroke (this would be all that black carbon that builds up on your tailpipe); however, it does aid in the prevention of engine knock that is counterproductive to the four stroke process..

In addition to adding fuel to the mixture to prevent pre-detonation of the air/fuel mixture, you can change the combustion properties of the fuel itself to make it less volatile; thus, less likely to ignite prior to full compression. This is accomplished by raising the octane level of the fuel by using additives. It is probably important to note at this point that octane levels are not a measure of potential energy in the fuel; rather, it is a measure of compressibility of the fuel. The higher the value, the more it can be compressed without self-igniting. As a result, you may notice that if you get a tune that increases the pressure that your turbo produces, you are also going to be required to use a "premium" fuel with a higher octane level.

Lastly, modern engines can change the planned detonation point within the ignition sequence. In truth, the entire combustion sequence occurs at a much slower rate than the engine is actually operating, so the spark plug actually fires and ignites the air/fuel mixture before the full compression stroke is complete (before top dead center) to take advantage of the potential energy of the expanding gases at its peak. It's a balancing act. You want to ignite the mixture before you actually want to use it, but you want to be able to compress the mixture as far as you can before igniting it to also take advantage of the expanding gases. The engine control unit (ECU) that controls when the spark plug fires can actually retard (delay) or advance the timing of the spark to optimize the power stroke while avoiding the dreaded engine knock. Your ECU is constantly monitoring such things as gas pedal position, RPMs, ambient and boost pressure, timing, ambient air and exhaust gas temperatures (EGTs) to determine how much fuel to add to the air coming into the engine and measuring the effectiveness of the combustion to make further adjustments to the fuel flow. It works endlessly and tirelessly to optimize the power stroke to pull as much energy out of the combustion as possible while also balancing the need to reduce particulate emissions from an incomplete burn cycle to meet environmental regulations.

How does a turbo work?

While I have said that the turbo is a simple air pump, it is actually more than just that. Any pump must have an energy source to operate. In the case of a supercharger, that energy is being supplied by the engine itself off of the accessory drive that also powers your power steering pump, alternator, air conditioning compressor, and your water pump. In the case of a turbo, the exhaust gases that are being expelled from your engine on the exhaust stroke creates the energy to operate the turbo. This has several advantages and disadvantages. The advantage is that if the turbo is properly sized so that minimal back pressure is created as a result of being directed through the turbine section of the turbo, it is free power that would normally be wasted. The disadvantage is that the power to rotate the turbine relies on how much exhaust gas is being expelled. Thus, turbos experience a phenomenon known as "turbo-lag" which is the time it takes for the exhaust gases to spin the turbine to a useful speed that can be in turn be used to compress air.

The turbine section of the turbo works much like a pinwheel. Exhaust gases are pulled into the turbine housing and spins the turbine wheel. After the hot gas passes through the turbine, it is expelled through the turbine exhaust into your exhaust system. The efficiency of the turbine is measured by determining the ratio between the area within the turbine housing and the radius of the bend around the turbine wheel (A/R ratio) which determines how much exhaust can pass through the turbine section. A smaller A/R ratio number means the exhaust gases are being contricted which increases the flow rate spinning the turbine wheel faster at lower exhaust gas pressures. In contrast, a larger A/R ratio number means that the turbine section has a larger volume and requires a higher density of exhaust gas to spin up. With that said, one would wonder why anyone would go with a larger turbine setup. The answer to that question rests on how much gas can pass through the turbine inlet at a given pressure and the optimal speed the turbine wheel was designed to operate at. We can assume that a cylinder has a set volume and as a result the volume of waste gas that is expelled from the cylinder during the exhaust stroke is constant regardless of engine speed. As a result the amount of exhaust gas that engine can push out increases linearly with engine speed; however, the pressure required to push the exhaust gas through the turbine housing increases exponentially. At some point the pressure required to push more gas through the housing exceeds the pressure of the hot gases being pushed out of each cylinder resulting in back pressure. So, while a turbine section with a small A/R will spool faster on less exhaust gas, it will reach its peak efficiency sooner and any additional exhaust gases added will have to be dumped through a wastegate to prevent the escaping gas back pressure to increase to a point where the exhaust gases cannot be efficiently evacuated from each cylinder. A large A/R turbine section, while being less efficient at lower RPM levels will peak in efficiency at a much higher RPM, taking advantage of the additional exhaust gases produced at higher RPM levels and producing more power. The stock turbo on the Genesis Coupe is designed to peak early in the RPM range and take advantage of less exhaust flow thereby reducing the turbo lag; however, this design limits the peak power output of the stock turbo to about 240-260 wheel horsepower (whp) on the 10-12 models and about 290-320 (whp) on later models.

The second measure of efficiency for turbos is a value known as trim. Trim is a the ratio between the size of the inducer portion of the turbine wheel and the exducer portion of the turbine wheel. This ratio determines the geometry of the turbine wheel and describes how efficient the wheel converts exhaust gas into rotational energy or how well rotational energy is used to move and compress air. The turbo consist of two sets of turbine wheels that are opposites in design. The turbine wheel in the turbine section of the turbo has an inducer that is larger than the exducer. On the compressor side, it is the opposite and the exducer is much larger than the inducer. This is because of the way that gases/air flows in/around/and through the turbo. In the case of the turbine section, exhaust gases are introduced at the outer edge of the turbine wheel and is expelled through the center. The air in the compressor section is introduced in the center and pushed outward around the compressor housing and out through the intake plumbing. For the purposes of this discussion, trim refers to the inducer/exducer ratio of the compressor section. Smaller trim compressor wheels spin up faster, but as with the A/R ratios, reach its efficiency peak faster, whereas higher trim ratios allow the turbine to compress more air but work slower and reach their peak later. The size of the turbine wheel is limited by the size of the turbine/compressor housing; thus, it is typical to see smaller trims associated with smaller A/R housings.


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Discussion Starter #16 (Edited)
Turbo Basics... what's it all mean? (cont.)

How does this all come together? There are several factors that determine how large a turbo can be used efficiently in a given application. First, is how much exhaust gas is there to use. Second, what is the peak RPM that the engine can handle. Third, how much pressure can the engine take. Lastly, how much lag can you tolerate? As with other balancing acts, you want a turbo that spools as early as possible but does not peak in performance before the engine is spooled out. For our engines, that peak point is about 7000 rpm. Yes, I know that some tunes will allow the engine to spool to 7200 RPM, but given the varying degrees of tolerance in quality of the stock Theta II motor, spooling to 7200 rpm regularly can be a detrimental act with regard to engine life due to the fact that the engine has not been balanced for high RPM operation.

In the world of turbos, bigger is not necessarily better. Larger engines produce more exhaust; thus, can take advantage of a larger turbo with higher A/R and trim ratios with less lag; however, they may be limited in terms of the speed at which the engine can turn (bigger engine, more moving parts, more balance issues). In twin turbine applications, the efficient size of the turbo may be comparable to what is efficient in a smaller engine because the exhaust is split between the cylinders. Properly sizing the turbo to take advantage and operate most efficiently through the largest portion of the RPM range of the engine will produce the most amount of power. A turbo that is too large will reduce the power band on the low end of the RPM spectrum and be wasted on the top end because the engine cannot spool fast enough to take advantage of it and a turbo that is too small will peak too early in the RPM range and not be able to produce additional power on the top end. Additionally, you must consider that a turbo that is too small may increase the back pressure on the exhaust which in turn prevents the engine from fully expelling all of the exhaust from its cylinders on the exhaust stroke. In the end, this back pressure can reduce power as some exhaust residue will be left over in the cylinder as it is trying to pull in additional air/fuel from the intake manifold.

Ideally, you want a turbo that spools as early as possible but does not reach its peak flow capacity until about 7000 RPM. While balancing the A/R ratio and trim wheel size can optimize the turbo's function, a twin scroll turbo might be the answer that solves both problems of low end power and high end efficiency with fewer compromises. A twin scroll turbo is capable of changing its wheel geometry (trim) to optimize spin rates for low and high RPM applications. Twin scroll turbos do this by essentially splitting the exhaust into two parts and then pushing those gases between two separate sets of spirals (scrolls) on the turbine wheel. When one set of scrolls loses efficiency due to high or low exhaust flow, the other set of scrolls is operating at peak efficiency. The stock turbo in the later generations of the Genesis Coupe is a twin scroll turbo that allows for boost at the same point or slightly earlier than the 10-12 stock turbo while allowing it to operate more efficiently at higher RPMs where the 10-12 stock turbos tend to peter out. The result is comparable lag of the 10-12 Genesis Coupes with a higher top end output.

One might immediately jump on the fact that the twin scroll turbo is definitely more bang for the buck, and you would not be wrong. You might also wonder why all aftermarket options are not twin scroll. The reason for this is a bit more complicated. First, the twin scroll turbo requires a twin scroll exhaust manifold. While this in of itself is not necessarily a big deal, it does add to the cost of an upgrade because you will be changing more components. Secondly, your engine may not be able to handle too much power early in the RPM range. Engine power is most directly measured in terms of torque produced. As the engine spins faster it requires less torque to spin even faster; thus, the opposite is also true. If the engine is spinning slowly, it requires much more torque earlier in the power range to gain speed. While the newer generation of Genesis Coupes have forged rods, the 10-12 models have weaker cast iron rods. What this translates to is that the older models cannot handle a large amount of torque too early in the power range without failing. Single scroll turbos spool more slowly than twin scroll turbos and produce less torque in the low power ranges. This puts less strain on the engine and reduces the chance of rod failure. Before considering a twin scroll turbo on an earlier model Genesis Coupe, you will have to upgrade the rods in order to handle the torque that will be produced lower in the power range. Again, the choice comes down to cost and what you are willing to spend on your build. If tearing into the internals of your engine is not in the budget, a twin scroll turbo is not your answer.

Twin scroll vs single scroll turbo

So... the question comes down to what turbo is right for me? The answer is not as straight forward as you may have hoped. The answer is the turbo that is right for you is the one that you can afford. The Theta II engine on this date is capable of producing up to 700 whp with the right turbo and engine build modifications. You will spend quite a bit of money to get it there, but it is a very capable platform. Lesser and more affordable options will get you to 300 whp (10-12 models) up to 600 whp (all models) depending on how much you are willing to spend to get it there. The higher you go, the more you will spend building your engine to handle the torque of higher power levels. Additionally, for the highest power levels, you will want to increase the RPM range of the motor to handle higher spin rates, which means balancing and blueprinting the engine. You could save yourself a bit of trouble by purchasing a long or short block that has already been built up to handle additional power. While this route may save a lot of aggravation and guessing, you will spend a good chunk of change to purchase a pre-built engine that essentially comes with no warranty (no vendor is going to provide you with a warranty knowing that you are modifying it to produce an insane amount of power).

There are essentially two routes you can go for turbo selection: Route 1 - Purchase a package deal from one of our vendors who have already done the research for you and have worked out most of the kinks; Route 2 - Do the math yourself, buy all the parts yourself, and figure it out on your own. Route 1 has the advantage of simplicity and may or may not be the most expensive path depending on how much you know and who you know. Route 2 has the advantage of customizing the build to your specifications and requirements and may or may not save you money depending on how much you know and who you know. There is the Route 3 option as well. Route 3 - Give your car to a builder and let him/her do all the work and give you a car that is done. This route has the advantage of simplicity; however, it is most likely going to be your most expensive option. In some cases, the builder may even provide you with a limited warranty since s/he knows what went into the build and tunes it for what they believe is "safe". At the end of this route you may find that you have spent as much on the build as you would have spent purchasing a brand new twin turbo Porsche, but who am I to tell you how to spend your money?

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Discussion Starter #17 (Edited)
Water / Methanol Injection... do I need it?

The idea of injecting water into your engine is probably the least intuitive thing that one could think about doing; however, there is a science that supports water and/or water mixed with methanol injection that can support large power builds safely.

What is methanol?

Methanol also goes by the names “wood alcohol,” “methyl alcohol” and “methyl hydrate.” It is the same common alcohol used in “alcohol-burning” race cars. It is commonly used as antifreeze in -20° F blue winterblend windshield washer fluid, as well as a gasoline dryer in “Heet.” It is also used for keeping air lines dry in trucks that have airbrakes. Methanol is a high octane fuel that is also extremely resistant to detonation. It has a tendency to absorb heat out of the air – something known as latent heat of vaporization. The water also absorbs heat and provides a further cooling effect as the finely atomized water/methanol mix is pumped into the engine. The cooler, denser intake charge reduces the chances of detonation even as the high-octane methanol boosts power.

A little history on water / methanol injection and who figured all of this out...

An engineer by the name of Sir Harry Ricardo is usually associated with being the first person to really start to use water injection in the early ’40s. He originally experimented with using water to increase the effective fuel octane ratings to allow for increased power on high boost spark ignition aircraft engine applications. This was usually used to aid in take offs during WWII and to increase the working ceiling of air breathing engines. It was also used to help fighter aircrafts gain the upper hand in dogfights.

Even after WWII water injection was used but other advances in gasoline chemistry made this less and less needed. Most manufacturers preferred to build engines that are able to run at maximum output with the least external assistance needed (i.e. only adding fuel to the fuel tank).

Water is the ultimate octane booster!

Octane, as discussed in earlier articles, is a measure of how resistant fuel is to combusting under compression. When a piston compresses the air / fuel mixture heat is produced (yes... even before the spark). If the fuel has a very low octane rating, that fuel can ignite itself causing a condition that is commonly refered to as knock. Thus in high compression engines and forced induction aided engines, using higher octane fuel can allow for higher compression ratios and more pressure safely. Most tunes take advantage of the higher octane by advancing timing and allowing for higher boost pressures; however, there are limits to how much timing and boost can be safely applied given the fuels that are available commercially. Water inhibits the tendency of fuel to ignite under pressure and raises the octane rating of the air / fuel mixture in the cylinder to allow for even higher boost limits and more aggressive timed tunes.

Water and methanol are cooling agents!

Cooling is accomplished through evaporation. While water has a greater cooling capacity than methanol by volume, it takes far more energy to evaporate water than methanol. A 50/50 mixture of water and methanol allows for the greatest cooling effect. Cool air is dense air. While the volume of air going into the cylinder remains unchanged regardless of temperature, the actual number of air molecules entering the cylinder is dependent upon the density of that air. Denser air = bigger bang... so it follows that bigger bang = MORE POWER!

So... How does it all work?

As the liquid water/methanol mixture enters the intake, it absorbs heat energy from the surrounding air and travels along with the air. As the mixture enters the cylinder and as the intake valve closes, the liquid continues to absorb heat energy. When the piston starts to compress the mixture, it stays above what is called the saturation temperature (the temperature at which a liquid under goes a phase change converting into a gas, like boiling water, at a given temperature).

As the piston continues to compress the mixture, the liquid is able to absorb more and more heat energy. Then, once the fuel is injected into the cylinder and ignited, the temperature reaches the saturation point and the liquid becomes a vapor (or gas). During this phase change, the oxygen molecules from the water are able to interact with the fuel molecules to provide extra oxygen for combustion. While straight water doesn’t contribute to significant horsepower gains, this process does help to lower combustion temperatures. As the percentage of methanol that is introduced into this equation rises, more power is produced (thanks to the burning of the methanol).

What are the advantages of water / methanol injection?

  1. More power: the high-octane properties of methanol, along with air cooling properties of the methanol and water, help water/methanol systems produce more power. In addition, the cooler intake temperatures allow you to run more aggressive timing and/or boost (forced induction applications) without increasing the chance of detonation. If tuned to take advantage of the water / methanol injection kit, boost can be turned up and timing can be advanced to a more aggressive setting to produce more power. The water / methanol mixture without a tune will not add power.

  2. Efficiency: leaner air fuel ratio can be utilized for normal operation. A major reason why tuners and car manufacturers run their cars richer is, in part, to use the fuel itself as a cooling agent to prevent pre-detonation.

  3. Low cost: water/methanol systems start around $300. The cost of the water / methanol mix itself costs a little more than a gallon of premium gasoline.

  4. More economical for the street: water/methanol is a less expensive high-octane alternative to pure race gas for guys running high compression engines on the street.

  5. Built-in engine maintenance: in some cases, the atomized water effectively steam cleans the valves, valve seats, and even the piston tops and intake, reducing carbon buildup.

  6. Both Naturally Aspirated (NA) and Forced Induction (FI) engines can benefit from water / methanol injection.

What are the disadvantages of water / methanol injection?

  1. If tuned to take advantage of water / methanol injection you need either a failsafe that limits boost in the event that you run out of mixture or you need to make sure that you don't run out.

  2. Not tuning for water / methanol injection can result in some power loss. Methanol contains far less potential energy than gasoline... water contains no inherent energy with regard to the combustion process. If you are not going to tune to take advantage of the water/methanol injection, reduce the flow rate to take advantage of the cooling properties of the solution without diluting the air/fuel mixture.

  3. You have to find room in your car that is away from heat sources to store the methanol. This is generally not a huge problem, but still something to think about. Some folks have used their windshield washer reservoir and dual purposed it as a meth storage tank. This will work (a 50/50 mixture of water/methanol is actually a great windshield washer fluid); however, be aware that most windshield washer fluid tanks are quite small and you will find yourself filling the tank quite often.

  4. Adding a water / methanol injection system is going to require you to be diligent in maintaining that system. Although a 50/50 mixture of water/methanol is not flammable, you don't want leaks as that reduces the efficiency of the system. You definitely want to be able to monitor your AFRs which means that if you do not have a Wideband O2 gauge, get one! When the pump stops working or an injector gets clogged, it can be difficult to diagnose a problem.

  5. Weight! For those of you who are concerned with weight, keep in mind that water weighs about 8 lbs per gallon. The larger your tank, the more weight you add. It's not a lot, but if you are fanatical about weight reduction this is certainly a factor.

  6. The effectiveness of water / methanol injection is dependent upon on evaporation which is depend upon proper atomization of the mixture. Extremely humid air or cold air can affect how much evaporation occurs or how well the air absorbs the mixture.

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Discussion Starter #18

How much water / methanol do I need to spray?

That would all depend on why you are spraying. If you are only using the water / methanol mixture for cooling, you can get away with spraying as little as 15% of your total fuel flow. This will reduce the temperature of the charge air and allow the ECU to take advantage of the higher octane which will result in a bit more power and much safer driving conditions. For forced induction or high compression modifications that are tuned to take advantage of the additional octane and cooling properties of the water/meth injection, you can spray as much as 25% of your total fuel flow depending on what your tune requires. Most water/meth injection kit manufacturers will have recommended spray values based on their kit.

What kind of fluid do I need to use?

There are several companies that sell premixed water methanol mixes. All use distilled water (water that has had all of the minerals filtered out <~~~ IMPORTANT) and purified methanol with no additives. The nice thing about using a premix is that you know that you are getting a precise mixture of water/methanol at a controlled ratio that is close to 50/50. With that said, you do not have to use the premix. Blue windshield washer fluid that is good to -20 degrees fahrenheit contains approximately 31% methanol and purified water. Some may have a small percentage of cleaning solution which you should try to avoid but will not be detrimental to your engine. HEET, a fuel drying product, is 99.5% methanol. Mix three bottles of HEET with your -20 degree windshield washer fluid and you have a 50/50 mixture of water / methanol that you can use in your injection system. You can also purchase methanol in bulk and use distilled water to mix your own; however, that is a bit more challenging and 100% pure methanol is flammable with a very low flashpoint. Not something you would probably want to store in bulk in your garage. WARNING: Do not use any windshield washer fluid that isn't blue. Also, if you find windshield washer fluid that goes below -20 degrees, make sure it does not contain ethylene glycol. Also, do NOT use E85 or ethanol fuels in your tank. In a pinch, you can use isopropyl alcohol (rubbing alcohol) or denatured alcohol, but both have lower energy by content and lower latent heat vaporization and will not be as effective as methanol.

Do I need to buy a kit or can I just make one on my own?

There are some very complicated equations that go into developing an efficient water/meth kit that would be difficult to duplicate on your own. First off, you will need a pump that can pressurize the fluid to at least 50 psi for proper atomization, specialize spray nozzles... again for proper atomization, and a control apparatice that controls how much fluid is sprayed and when. If you were to buy all the pieces parts separately you would end up spending far more than the price of a baseline water/meth kit.

How much heat will the water/meth mixture absorb?

Water/meth mixed at a 50/50 mixture sprayed at 15% of the fuel rate of flow will absorb between 50-150 degrees celsius (122-302 degrees fahrenheit) of heat depending on atmospheric conditions. When combined with your intercooler, this can reduce intake air temperatures from 0-10 degrees above ambient temperatures. You will never see temperatures below ambient air temps, but you can get as close to them as possible. Heat is an engine's enemy with regard to air charge. The higher the air temperature, the lower the potential energy of the air/fuel mixture and the greater the possibility of pre-detonation. Cooling the air charge as much as possible reduces the possibility of engine damage while also allowing you to unlock the full potential of your engine.

My car isnt knocking now, why do I care?

Safety, safety, safety. One tank of bad gas can destroy a tuned engine. If you want to limit the chances of pre-detonation, water/meth injection is the answer.

Is it better to inject the water/methanol solution before or after the Turbo? Where is the best place for my car?

There has been more discussion recently on the internet advocating pre-turbo injection. Most of the debate centers around increased atomization. You can probably get away with this in the short run if you inject a small quantity of finely atomized fluid (less than 10micron droplet) with a very low injection duty cycle. Also if you don’t care about turbo longevity (like some race applications where the turbo is replaced frequently) or you have a system that doesn’t atomize correctly and need the turbulence to help (low injection pressure and nozzles that aren’t designed to atomize correctly). In diesels, especially where injection quantities are large in relation to fuel and where there is benefit to injecting at low/mid engine load states on up, it becomes a question of when compressor wheel damage becomes too severe as pre-turbo injection has been proven to cause compressor wheel erosion. The amount of erosion depends on the quantity injected, the size of the droplet injected, the speed of the compressor wheel, and the injection duty cycle (what % of total engine operation is water-methanol injected). Also, the argument of reduction in compressor work per unit flow and the increase in mass flow rate doesn’t hold water in a properly sized modern non-wastegated turbo. For most applications on the Genesis Coupe, adding the injector right after the throttle body is the most effective location for the injector spray nozzle.

Can I install the injector nozzle before the intercooler?

You can but because the intercooler's design is to cool hot compressed air coming from the turbo, much of the water/meth mixture will be squeezed out during the cooling process and pool inside of your intercooler. YOu lose much of the cooling properties of the solution and water inside of your intercooler is a bad thing... don't do it.

Is there any benefit to spraying nitrous in addition to water/meth?

Nitrous Oxide increases the amount of oxygen available to the engine to create a bigger bang. It also provides a cooling effect much like the water/meth mixture does... so yes... adding nitrous oxide can increase the power significantly either by itself or if used in combination with water/meth. In fact, Snow Performance has an additive that can be added to their water/meth mixture that contains nitromethane which, when broken down by heat, adds oxygen to the combustion process.

Can I run water/meth without a tune?

Yes but you will not see much in the way of added power if you are already running 93 octane fuel. The ECU can compensate for higher octane fuels up to 93, but not higher. With water/meth injection you will typically see effective octane levels exceeding 100 octane but not usually higher than 115 octane depending on how much solution you are spraying and atmospheric conditions.

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Discussion Starter #19 (Edited)
Understanding Suspension Tuning

There seems to be a lot of misunderstanding about suspension tuning... what to do, why it's done.... so I decided to dedicate a section to suspension tuning to help those who know nothing understand the basics about what to do and why. As with other parts of this thread, this is not a how to guide; rather, it is and educational article to enable you to make sound decisions when planning your suspension tuning goals.

Before I get started, it is important to note that suspension tuning is like any other type of customization, what you do and how you do it really depends on what your goals are and what you plan on doing with the car. If you are only interested in the slammed look and you don't care that your car handles like a log wagon and handles like a Mack truck, this section is not for you. This section is dedicated to those who want understand how to get the best handling characteristics out of their cars... cost notwithstanding.

Before we get started we need to understand a few basic handling characteristics that affect all cars:

1) Body Roll (lateral and longitudinal)
2) Understeer
3) Oversteer
4) Wheel and Chassis Alignment
5) Body weight
6) Tire selection and configuration
7) Suspension accessories

Body Roll

Body roll is caused by how much weight is shifted when a car changes speed and/or changes direction. A perfectly balanced car that has the exact same weight on each wheel is only balanced when the car is sitting static. What the car does when it is moving has little to do with how it started when it was not moving. There are several things that impact body roll directly, the most obvious being spring rate of the coil springs that hold the car up on its suspension. The second thing that impacts body roll, or more specifically the speed at which the body rolls is the dampener rate of the shock absorber / strut. The last thing to consider when discussing body roll is the rigidity of the frame of the vehicle itself. The more flex in the frame, the more the roll tends to affect other things.


Springs are not springs. There are two types of springs that are available for the Genesis Coupe. The first type of spring is the OEM spring or aftermarket lowering springs that tend to mimic the response of OEM springs and that is a progressive type of spring. Manufacturers use progressive springs for primarily one reason, that is the comfort of the driver and the passenger. Progressive springs start with a relatively mild spring rate that reacts quickly to imperfections in the road to smooth out the ride by absorbing most of the vertical movement of the wheel that would normally be transmitted to the frame. As the spring is progressively compressed, the spring rate increases to give the car stability and reduce body roll. While progressive springs work well in the daily driving environment to provide a comfortable ride, they tend to feel "mushy" and reduce road feel as the springs prevent the imperfections in the road from being transmitted to the driver. As a result, progressive springs can feel imprecise and unpredictable in high-speed track conditions.

The other type of spring you will find in the aftermarket is a linear spring. A linear spring differs from a progressive spring in that it produces the same amount of resistance throughout its compression range. If the progressive spring is unpredictable and imprecise, the linear spring is more predictable and more precise because the spring rate does not change depending on how much it is compressed. This is why linear springs tend to be part of performance upgrade kits. The downside of linear springs is that they do not do a good job of absorbing small bumps so the ride, even at slow speed, tends to be a bit rougher.

There is a third type of spring that, as far as I know at the time of this writing, is not available for the Genesis Coupe, and that is the dual rate spring. The dual rate spring has two sections of spring that provides two different spring rates. This is the closest thing to having the best of both worlds as the spring rates tend to be linear in each section and the section with the lighter spring rate handles most of the comfort issues that single rate linear springs have. You have a soft section for most daily driving situations and you have a stiffer section to handle the hard curves of a nice mountain road.

Spring rates

There is much debate as to what the perfect spring rate for a Genesis Coupe is. The reason for the debate is often a question of what you want to do with the car and how you want it to perform. Spring rates will have a direct effect on tire grip, body roll, and impact oversteer and understeer as we will discuss later in this section. Choosing the right spring rate for what you want to do will make a big difference in how the car handles. Remember, the higher the spring rate, the rougher the ride and vice versa. Like most performance dilemmas, tuning your suspension often requires that you choose one priority over another in order to gain the performance that you want.

Drag Racing - When a car rapidly accelerates the weight of the car will tend to shift back as the entire chassis of the car tries to rotate against the spin of the wheel. For those of you who fell asleep during High School science, the principle is governed by Newton's Third Law of Motion, "For every action, there is an equal and opposite reaction". So, while your tires are trying to rotate forwards, the rest of the car is trying to rotate backwards which shifts the weight of the car on to the rear wheels. If you plan on drag racing your car, you want to encourage this behavior and you would want to go with a low spring rate in the back so that the car will squat on the drive wheels and produce even more grip than it had sitting static.

Track - Performance on the track is very different from performance in straight-line racing. You have to remember that you are trying to balance two different parts of the car... the part of the car that is responsible for acceleration and the part of the car that is responsible for steering and stopping. We have already discussed the part of the car responsible for acceleration in the previous paragraph about drag racing, so let's concentrate our effort on the wheels that are responsible for steering and stopping.

When you apply the brakes, Newton's First Law of Motion kicks in, "A body in motion tends to stay in motion unless acted upon by an outside force". When you apply your brakes the wheels will tend to be the first things that slow down while the rest of the car tends to want to continue at the speed it was traveling. What you end up with is a rotational force towards the front of the car with the nose of the car diving and the weight of the car shifts forward. While some digging in is not necessarily a bad thing as the weight of the car moves towards the two wheels that have the biggest brakes (ever wonder why your front brakes are bigger than your rear brakes?), too much shifting and movement can have an adverse effect on steering and your alignment.

Hard braking into a turn tends to induce a condition known as oversteer which and again we will be discussing later in this article; however, in its simplest terms, oversteer is the tendency for the back end of the car to kick out in a turn. To reduce oversteer going into a hard turn while braking you will need a heavier spring up front to reduce the amount of weight shift forward. The tradeoff here is that you will lose some braking performance, as there will not be as much weight on the tires that are trying to slow the car down. More importantly, you want lighter springs in the back so that when you accelerate out of the turn that your back wheels don't break loose from the pavement and induce oversteer which tends to kick the back of the car out.

How much spring rate do I need? That is a very good question, I'm glad you asked. As much as you need and not more. I know you are thinking to yourself that isn't exactly the answer you were looking for. The good thing is that you don't really need a straight forward answer as long as you understand a few basic concepts. First, what we had discussed with regard to spring rates front and back and when you want higher spring rates in one of the two positions. The second is that spring rates will determine how much force is required to compress the spring. The higher the spring rate, the more force it takes to compress the spring. Lastly, if you've read the text so far, you know that higher spring rates result in less body roll and as a result less weight shifting but also increase ride harshness. With these three bits of knowledge you have acquired up to this point you can look at a spring or coil over set and determine how the ride is going to feel just by looking at the numbers. You should also be able to get an idea of how the springs are set up with regard to how they should perform and for what purpose. If you see a higher spring rate in the rear, you know that it is probably more of a track type setup. If you see a higher spring rate in the front, you know that it is most likely set up for drag racing. The lower the spring rate, the closer you get to OEM ride comfort.

OEM Spring rates - Keep in mind that OEM springs are progressive, so there's not a single spring rate that can be measure throughout its compression range; however, with that in mind, if OEM springs were linear instead of progressive the spring rates would be:

• Non-Track or R-Spec - F: 2.52 kg/mm, R: 6.51 kg/mm (1:2.58 ratio)
• Track or R-Spec - F: 2.75 kg/mm, R: 6.34 kg/mm (1:2.31 ratio)​

Note: Spring rates are measured by determining how much force is required to compress the spring one millimeter. The number itself is not necessarily and indicator of how much weight the spring will hold.

Notice that the OEM springs are actually quite light. Keep in mind that the Genesis Coupe has a very stiff frame and sub frame. As a result the spring rates are considerably lower than what you would find on other cars from the factory. More important than the spring rates, notice the spring rate ratios from front to back. The ratio decreases when you go from your street version of the car to more of a track version. We'll discuss more about how spring rates affect the overall handling of the car and what you should be looking for later.

Spring damping

Spring dampeners or as you may have heard, shock absorbers, determines how quickly a spring is allowed to compress or relax regardless of the amount of weight or force that is applied to the spring. So... here's where we need to clear up a few misunderstandings about what a shock absorber / dampener, hereinafter referred to as the dampener, does in relation to the spring.

1) The dampener does not determine ride height. Ride height is determined by the length of the spring holding up the car. A strut does not hold up the car.

2) The dampener is not a spring.

3) The dampener will determine how fast the spring moves by providing a damping force that moderates the spring’s natural tendency to "bounce".

4) In multi-link applications where the spring and the dampener are two separate parts, the dampener can be used to prevent the suspension control arm from dropping so far as to allow the spring to come out of its pocket (preload).

5) The dampener limits the amount of vertical movement of the suspension control arm.

With these things in mind, the next thing to think about is the difference between the OEM strut and aftermarket alternatives. Front suspension uses what is known as a MacPherson strut. The strut is mounted vertically from the wheel and attaches to the car frame at the strut tower. These struts are coilover type struts in that the dampener and the coil spring are contained in one assembly. These struts are non-adjustable. The basic workings of the dampener are really quite simple and it involves a gas charge, a piston shaft attached to a piston with valves, two oil reservoirs, and a viscous (dense) fluid. When the piston compresses fluid is allowed to travel through the piston valve from one chamber to another which serves to slow down the motion of the piston arm by providing resistance since the fluid can only travel so fast from one chamber to the other. A gas charge at the bottom of the cylinder acts as a spring in the event that more movement is required faster than the viscous fluid can travel through the piston valve to its opposite chamber.

By slowing the compression or relaxation of the spring you limit how fast the weight shifts from front to back and from side to side. Most mid-level and high end coilover kits as well as high end dampeners have an adjustment knob that will allow you to control how fluid flows from one chamber to the other by opening the control valve wider or narrower. Opening the valve allows fluid to transfer faster and closing the valve slows down the fluid transfer effectively changing the rate at which the strut dampens the spring movement.
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Discussion Starter #20 (Edited)

Understeer is the tendency for a car to continue in the direction it was traveling in a turn in spite of the direction the wheel is turned. In spite of how bad that sounds, understeer is generally considered more controllable than oversteer where the back end of the car kicks out in a turn as with understeer you can see where you are going. For this reason, most major car manufacturers who make cars for the masses will tend to err on the side of understeer rather than oversteer when they design their cars.

Let’s discuss some of the things that can induce an understeer condition:


• Weight distribution
• Drive layout
• Suspension & chassis setup
• Tire type, wear and pressures​


• Cornering speed
• Throttle
• Braking
• Steering inputs
• Weight transfer​

Understeer is most likely to result from the following scenarios (which are more difficult to correct as you move down the list):

• Accelerating into a corner
• Braking into a corner
• Ploughing into a corner too fast
• Low traction conditions on the corner​

Note that all but one factor is controllable by the driver. Aside from road conditions, knowing what your car is capable of doing will go a long way to avoiding a potential understeer situation.

While many of the factors that involve understeer can be controlled by the driver, there are adjustments that can be made to the suspension to reduce the car’s tendency to understeer:

Now that we understand understeer, it’s time to move on to oversteer. Oversteer is dangerous because most drivers do not react properly when it occurs. While intellectually we know to steer into the direction of the skid, the average driver will tend to over correct too slowly for an oversteer condition and cause the vehicle to oversteer in the opposite direction.

When reacted to properly a controlled oversteer condition turns into an epic drift and power slide. When reacted to poorly an uncontrolled oversteer condition usually ends with an epic crash sequence. Here are some of the things that can contribute to an oversteer condition:


• Weight distribution (front or rear bias)
• Engine and drive layout
• Suspension & chassis setup
• Tire type, wear and pressures​


• Cornering speed
• Throttle
• Braking
• Steering input
• Weight transfer​

There are four major active causes of oversteer, but what you're likely to encounter depends on the car being driven. Causes include:

• Entering the corner too fast
• Accelerating into the corner, too early or too aggressively
• Braking into the corner or mid corner
• Lifting off the throttle mid-corner. This scenario is also known as:​

o lift-off oversteer
o snap-oversteer
o trailing-throttle oversteer
o throttle off oversteer
o lift-throttle oversteer​

As you can see, almost all of the factors that can induce oversteer are directly related to driving style. Oversteer is usually a result of either intentional or unintentional inputs by the driver. Counter steering inputs must be both immediate and moderate (only enough to point the wheels in the direction of intended travel). Too much input too late will usually cause the back of the car to slide in the opposite direction when the correction is made if the steering input is not neutralized as the correction is made. There are some changes that can be made to the suspension to correct for a car’s tendency to oversteer:

Wheel and chassis alignment

Alignment is probably the least understood element of suspension tuning and arguably one of the most important elements. A bad alignment can totally screw up an otherwise decent suspension setup. Not only can a bad wheel alignment contribute to dangerous driving conditions, it can have an adverse impact on tire wear and gas mileage as a tire that does not track properly is most likely scrubbing on the road increasing friction and wear. There are three geometries that affect alignment, but only two of the three geometries can be adjusted on a Genesis Coupe.


Camber is the angle of the wheel, measured in degrees, when viewed from the front of the vehicle. If the top of the wheel is leaning out from the center of the car, then the camber is positive ,if it's leaning in, then the camber is negative. If the camber is out of adjustment, it will cause tire wear on one side of the tire's tread. If the camber is too far negative, for instance, then the tire will wear on the inside of the tread.

For many years, the trend has been to set the camber from zero to slightly positive to offset vehicle loading, however the current trend is to slightly negative settings to increase vehicle stability and improve handling. It’s a well-known fact that he lateral (side) load a tire can withstand, without losing grip, can be increased by adding negative camber. This increased grip effect continues to increase as the negative camber is increased by as much as 5 degrees.

Camber is adjustable on all Genesis Coupes in the rear; however, camber is only adjustable on OEM R-SPEC and Track trims where front camber adjustment bolts were provided as an additional part that was not installed at the factory. Other trim levels that did not come with front camber adjustment bolts can use R-Spec or Track camber adjustment bolts; however, must be purchased separately. Most coilovers have camber adjustment plates that can be used either in conjunction with or independently of the camber adjustment bolts.

Does negative camber have undesirable effects?

Yes. The best camber for maximum braking and acceleration is 0 degrees camber, which gives you the best contact patch and therefore the best performance with heavy braking and acceleration. Static negative camber will usually cause the inside of the tire to wear more than the outside. For directional or asymmetric tires, this can lead to more frequent tire changes as the tires cannot be rotated to even out the wear. At the end of the day, negative camber can improve cornering but you sacrifice braking and acceleration grip. For this reason, you should try to stay inside of manufacturer spec when applying negative camber. Staying within the spec ensures that most of the braking and/or acceleration grip is retained while maximizing corner grip.

Important alignment tip: When adjusting Camber, make sure that the left and right sides are adjusted to the same spec. Although camber does not directly affect steering, angling a tire in will tend to push the car in the direction that the tire is angled. If both tires on the same axle are not cambered the same, one tire will tend to push the car in the direction that has the most camber effectively causing the wheel to pull to one side or another.

What about suspension modifications like lowering a car?

Here is a little known fact that you probably don’t know… the manufacturer specification for camber is not derived for the car in a static condition; rather, it is optimized for the car moving at about 60 mph. Engineers understand that the car will be at a different ride height when moving down the highway and optimized the static alignment spec to give you the best camber setting while the car is moving.

In many cases, we can get the car to the static alignment specifications even after it has been lowered, but this does not mean the car will handle as well as before. Why, because the dynamic measurements – car loaded in a corner, body rolling 1 or more inches – will have the control arm in a different location than the non-lowered car which will affect the dynamic camber. For example, say a McPherson suspension set at 2.5 negative static camber at stock ride height has a dynamic camber in a 7 degree turn of 3.5 degrees negative. The car is lowered so the front lower control arm now goes up from the cross member (frame mounting point) to the lower ball joint by the wheel; it went down slightly before lowering. The static camber is re adjusted to the 2.5 negative setting, but the dynamic camber at the same 7 degree turn is now 2.5 degrees, not the more desirable 3.5 degrees. There is less impact on dual control arm cars, but the same phenomenon occurs. While lowering your car reduces the center of gravity of the car, the effect of negative camber is negated because of the range of motion of the control arm that is no longer level with the ground. The lower the drop, the less advantage you gain from negative camber in a turn. In the Genesis Coupe, lower is not necessarily better and lowering can actually hinder performance if taken too far.

Note: You cannot change the camber without affecting the toe; thus, camber adjustments should not be made in your garage using your eyeball or chairs and strings. Take your car to a competent alignment shop with the proper equipment to do a computer alignment. Talk to the alignment technician. If the alignment tech doesn’t know the difference between setting up a car for the street versus setting a car up for the track… leave.


The toe measurement is the difference in the distance between the front of the tires and the back of the tires. It is measured in fractions of an inch in the US and is usually set close to zero, which means that the wheels are parallel with each other. Toe-in means that the fronts of the tires are closer to each other than the rears. Toe-out is just the opposite. An incorrect toe-in will cause rapid tire wear to both tires equally.

Like camber, toe will change depending on vehicle speed. As aerodynamic forces change the riding height, the toe setting may change due to the geometry of the steering linkage in relation to the geometry of the suspension. Because of this, specifications are determined for a vehicle that is not moving based on the toe being at zero when the vehicle is at highway speed.

When you steer a car through a turn, the outside front wheel has to navigate a wider arc then the inside wheel. For this reason, the inside front wheel must steer at a sharper angle than the outside wheel.

Toe-out on turns is measured by the turning angle gauges (turn plates) that are a part of every wheel alignment machine. Either the readings are directly on the turn plate or they are measured electronically and displayed on the screen. Wheel alignment specifications will usually provide the measurements for toe-out on turns. They will give an angle for the inside wheel and the outside wheel such as 20 for the inside wheel and 18 for the outside wheel. Ideally you want to make sure that the readings are at zero on each side when the wheels are straight ahead, then turn the steering wheel so that the inside wheel is at the inside spec. then check the outside wheel. Cars with excessive toe in or toe out can cause significant wear on the tire and cause the wheel to pull hard in one direction or another. Toe specs left and right should be set as close to zero as possible, but definitely should be the same or near same from left to right.


The best way to visualize caster is to picture a shopping cart caster. The pivot of this type of caster, while not at an angle, intersects the ground ahead of the wheel contact patch. When the wheel is behind the pivot at the point where it contacts the ground, it is in positive caster. Picture yourself trying to push the cart and keep the wheel ahead of the pivot. The wheel will continually try to turn from straight ahead. That is what happens when a car has the caster set too far negative. Caster on a Genesis Coupe is not adjustable. If the caster setting is off, it is an indicator that something is bent or broken. Caster has no effect on tire wear but does have an effect on how the car tracks while moving forward. It also has an effect on how willing the car is to turn into a curve.

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