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3point8 Performance
2,628 Posts
Discussion Starter #1 (Edited)
If you've seen my previous thread: [How-To]: 3.8 Performance Upgrade Path Then you know I've been trying to get more from this engine for a long time. I've had so many people contact me over the forums, facebook and in person at events, telling me they based their build on my work and I usually hear, "I've done everything on your list except A,B,C but I'm doing those next!". I appreciate all of the feedback and comments too!

I've learned so much more since I wrote that last guide and now it's time for a serious update! This is the 3.8 Performance Upgrade Path V2. I will include both BK2 and BK1 relevant items and will include more drivability mods as well. There will be some new stuff, some old stuff and some changes on opinion from the last write up. I'll also include info on mods that people ask about and provide info on whether you should consider them or not.

So, here is my latest dyno result. 346HP / 292TQ

I've spent the last 3 years working on different things to try out. I've spent countless hours on the dyno, under the car, in the engine, in books, talking with tuners, etc to get ideas and test them out. My goal has always been to help the average 3.8 owner build a fun, well rounded car and get the most from it with the budget they have. I've been hassled about not just doing a turbo build and that's the common response when someone asks how to get more from their build. Sure, if you're looking for the maximum power possible, a turbo is the way to get there.

I see a lot of guys spending money in the wrong places and buying incorrect parts. There is a lot of misinformation and lack of understanding about how things work and I always try to improve that with facts and data and proving it all using my own vehicles.**

Not everyone is looking for a 700whp monster and to be honest, most Genesis owners couldn't handle it anyway. Some people like canyon runs, or auto cross, or road courses. Not everyone wants to do freeway pulls or 1/4 mile runs. So there is really no one correct answer to building a car because it's all personal and based on your goals and budget. Build the car based on what is important to you.*

As stated, my goal is to give the information needed to build a fun, well rounded car with max gains without breaking the bank and for the most part, that will be good enough for most. I'll have Turbo build information down below as well as info on other power adders.

Setting Expectations
I want to clear up some things that are not well understood. If you are following someone elses build, there is no way you will make more power than they did unless you go above and beyond what they did. I bring this up because it's getting far more common to hear people claiming numbers because they feel good to say. You are welcome to say whatever you want, but you will need to have definitive data to back up your claims. Please don't make statements without proof because it leads to newer guys getting their hopes up and then getting disappointed.*

I do believe there is far more to get out of these 3.8's, but FBO + custom tune builds will always net around the same power levels. So, if no one has made 400whp with FBO, then you shouldn't expect yours to do so either. There is a great thread with all sorts of dynos and mods here 2013+ V6 Dynos*so you can see realistically what to expect. It's also a fun thread to see the progression of the power levels over the years.

The Sad Truth
Ever hear, "your car was made on a Friday"? I have. I've had a tuner tell me that I must have bought a Friday car when his tune was sh*t and I proved it to him with data logs (previous car, not the gen). Well, if you're not familiar with this, it means that you got a car that was assembled on a Friday, when no one cares because they're thinking about the weekend so basically they produced sh*t.

This applies to the Gen Coupe 100%. The inconsistency in these motors is just amazing. Take two 2014 3.8s and one might make 10-15 more whp than the other with the exact same mods and tuning. Some 3.8s don't last long under abuse (Friday car) and others take the abuse and ask for more (Monday car). A Monday car, meaning everyone is refreshed after their weekend so they assemble the car with extra care, is what you want to have.

It's the sad truth, but the absolute garbage QC that hyundai does is scary and makes these cars vary wildly. You could have a Friday car while your buddy has a Monday car so don't be surprised if he makes more than you or is faster with the same mods. You can see what I mean with this thread here: Taking care of these issues can go a long way.

Mod Stacking
Mod stacking is a very misunderstood concept. If you took a 100hp stock engine and added 5 mods that each claim to add 10hp, you would not end up with 150hp in the end. You'll most likely end up with 120-130. Why? Because those numbers you see advertised are all taken against a stock setup when it's most sensitive to change (least efficient). The more mods you add, the fewer gains you'll get from each mod because the efficiency of the engine is increasing with each previous mod, so you have diminishing returns.

Not only that, even if it was dyno proven that a mod showed a gain of 10hp, it doesn't mean your setup will also see that same 10hp gain. Remember, companies selling products work hard to get the conditions absolutely perfect to get the best results because it means more sales.

Comparing Dyno Sheets
Dynos are tools. They should be used only to test before/after changes for your particular car and the same dyno should be used always. Comparing your dyno to someone elses dyno is a fun game, but it's little more than penis wagging and the data is meaningless. The type of dyno used and how that dyno is setup plays the most important part in the numbers reached so you might make 300whp on one dyno and 500whp on a different dyno.

Peak Power vs The Curve
Too much emphasis is placed on peak power. The overall curve is what you should really be concerned about. There are plenty of 500whp cars that are slow as hell because they are peaky and have almost no curve. So just because your friend has 350whp and you only have 330whp doesn't necessarily mean he'll beat you in a race.

Which curve do you think would be the best curve for street use and which do you think would be best for advertising?


3point8 Performance
2,628 Posts
Discussion Starter #2
Where Do I Start?
First is maintenance. If you're not taking car of your car, your car isn't going to take care of you. Take care of your car better than you take care of yourself.

Lot of controversy around this, but Mobil 1 Full synthetic or Rotella T6 should be used. If you're planning to get a turbo kit, then switch to Rotella T6 as it's been proven that Mobil 1 has issues handling it.

  • Change your oil when it's needed. Use Napa Gold or Wix filters (same thing).*
  • Check your oil level often! Lot of 3.8's with spun bearings because of oil starvation with too aggressive driving. If it's low, fill it up.*
Rev Range
Another area of controversy, especially since the community likes to compare the gen to the 350z/370z HR guys. These engines (at the moment at least) do not make power past 6600. I was able to peak at 6700 and a lot of them don't make power past 6300. The curve falls off immediately after that so revving to 7200, 7500 and 8000 is a waste of time and is dangerous to your engine. The sump (your oil pan) will run dry as the engine sucks up all the oil and it can't return back to the pan fast enough so when you're spinning the crap out of your engine, you're risking running it dry and then you're going to spin a bearing and ruin the engine.*

There are a few people (myself included) that are working to improve the peak power range, and there are a few people working to improve the oil problem as well. So stay tuned because this situation will certainly be improved.*

Oil Additives
I'm going to recommend this even though there is only anecdotal evidence. Using*Liqui Moly (20002) Cera Tec Friction Modifier - 300 ml can potentially help prevent a catastrophe in the event of oil starvation. Some users have reported it fixing oil related issues with their gens and there are reports from race teams that stated it prevented spun bearings after oil pressure dropped. I've personally used this product several times and have not had any issues. It did seem to improve/stabilize*oil temperature swings both for new and old oil.

Again, I have no scientific data or proof, only anecdotal evidence so take this recommendation with a grain of salt. I do not know for sure if it will prevent a spun bearing, but I have reached out to a 3rd party tester and I am waiting for results.*

Use every 3rd or 4th oil change. Shake the can very well before adding it to the oil. I recommend adding half of your oil bottle to the engine, then adding the Cera Tec to the oil bottle, shaking well and then pouring into your engine to ensure it doesn't clump and it gets distributed better. Do not use every oil change. If you have a bad oil burn or do not have a catch can, you probably shouldn't use this until you fix those issues.

Spark Plugs
OEM plugs are NGK and they are great plugs. Change them every 30k or so or before you get tuned. No need to run a colder plug, there is absolutely no benefit of doing so and would only be required with a nitrous or turbo build. Gap the plugs to 0.036 (this can be hard since you'll need specific feeler gauge with that size). There is no benefit to running them at 0.040 (please do not run more than 0.040!!).

Trans Fluid
Don't neglect this. For MTs, use Redline MT-85 or for 2014-2016 you can stick with OEM fluid if you want. The Redline fluid is worse in the cold but better in higher performance/higher heat scenarios. Personally I liked the OEM fluid, but it wasn't able to perform at the track. For the AT you can stick with OEM as it's what Level 10 recommends.

The OEM coolant is long lasting, but I personally like to do a full flush every 30k. If you end up doing work that requires draining the coolant, you might as well flush it anyway. Just go to the dealer and a get a gallon of their fluid. It's Dark forest green and is not diluted. Mix 50/50 coolant with distilled water.

Differential Fluid
The interval for this will vary based on your usage. If you're out doing burnouts, launches from a dig or heavy motor sports, then check and change often. Redline 75W90 GL-5 GEAR OIL is pretty decent.

Valve Cleaning
BK1 setups don't have as bad of a problem as the BK2, but the valves still get dirty. Since BK2 3.8s are GDi, no fuel hits the valve and that means no cleaning can happen. Severe build up can happen as early as 10,000 miles on a brand new car (I've personally seen it with my car and a few customer cars). Adding a catch can will help this problem, but not prevent it fully. Cleaning the valves when they get really bad is a chore. I recently spent 6 hours cleaning all of my intake valves. The power loss from dirty valves is a real issue.

Using CRC GDI Intake Valve Cleaner before each oil change to help reduce the build up. If your valves are really bad, you'll need to manually clean them. Either by spending hours scraping the garbage off with picks, or trying to find a shop that will do a walnut blast. I personally pull all of the spark plugs, turn the engine over until the ports I want to work with are fully closed, fill the ports with engine degreaser and let them sit for a while. This softens up the carbon so it become sludge instead of hard chunks. Then I use a set of plastic pics to scrape away the garbage and use q-tips to help clean remove the material. Extremely time consuming, but worth it.

Change your oil afterwards.

Injector Cleaning
Unfortunately using top tier gas doesn't always mean you're keeping your system clean. It obviously helps, but you still need to clean out the fuel system. Every oil change, run a tank of gas with "HEET Fuel Injector Cleaner" HEET is mostly methanol but it also adds in cleaners, so it will remove any water from your fuel system in addition to cleaning the valves (BK1). If you park your car outside in wet or colder environments, then you might want to use this more often. This is the RED bottle, not the YELLOW bottle.*

Catch Can
This should be your first mod. Period. If you expect to drive your car aggressively then you had best get on. A catch can sits between your PCV valve and your intake. It collects the oil that would normally end up going into your cylinders. Oil in the combustion process is a bad idea. It will cause knock which will retard your timing (thus losing power) and will flat out gunk up your motor and leave carbon on your pistons. Over time your pistons will get carbon build up bad enough that it will cause hot spots which will forever prevent running advanced timing. Ask me how I know!

The solution is just to add a catch can. You can get an expensive one, or you can get a cheap one. I built one for $15 using an oil/water separator for an air compressor. It doesn't look as nice as some of the more expensive ones (it actually looks ugly AF), but it works.


3point8 Performance
2,628 Posts
Discussion Starter #3 (Edited)


The stock airbox on the BK2 is more than enough to make good power. I made 326 with the stock airbox. The only problem the stock air box suffers from is a weird dip in the TQ curve around 4500 RPM.*

Even tuning doesn't really fix this much. But a K&N drop in filter is a great way to get started. Testing with the K&N filter and with NO filter resulted in the same power curve.*

An SRI (Short Ram Intake) is one that has the filter sitting in the engine bay. These are known as hot air intakes for a damn good reason. These are actually WORSE than the stock airbox. The stock airbox is actually a true cold air intake. Don't waste your money. Even with the heat shield, they just heat soak and ruin power. Sure, you feel a difference when you first put it on and you're driving around when everything is nice a cool. Sit in traffic for 10 minutes and then try to do a pull and see how happy the car is then.

I've already beat this horse to death, but regardless of advertised gains, butt dyno results and perceived drops in intake temps, these are a waste of money and will always lose to a correct intake setup.

CAI (Cold Air Intakes) are the best way to go simply because they fix the TQ curve issue the stock airbox has. A lot of BK2 SRI's are sold as "CAI" but they are not.*

3" vs 3.5"
I've dyno proven that 3" diameter piping is the absolute best size, providing a +6whp gain over a 3.5" and a 2.75". Bigger is not better.

What to do?
Stock airbox with a K&N is a great way to get started and save money as it will take you far. The stock airbox just needs some heat mods (it's a true CAI, but it suffers a bit from heat soak) and to move the location is the IAT sensor from the stock location, to the top of the box. Most people defend their SRI purchase with data collected comparing stock IATs vs IATS with the SRI. These are invalid tests because the stock location for the IAT sensor is located in a dead zone where little to no air movement happens until much higher into the rpm range while with an SRI, it's put directly into the path of moving air, so of course it'll look like it's cooler.

When you're ready, you can easily build your own 3" CAI. The problem will be placing it into the fender as the washer fluid reservoir must move or be deleted. BK1 options come with a different reservoir, but at the moment there are no options for BK2. I deleted mine and have had no reason to want to put it back in. Plus, it's like an 8lbs weight reduction :)

Shave IAT sensor
This might sound funny, but i'm dead serious. Even after you move the sensor, the sensor is still very slow to respond to temperature changes which leads to the same issues of sensor reporting higher temps that what is actually coming in.

The problem is the sensor is encased in plastic and that plastic prevents air flow to the glass bead that is actually reading the temps. Not only that, the plastic casing is susceptible to heat soak which will provide false readings.

This is a very simple mod, but one that should be done with care. Take a brand new razor and ever so gently start shaving plastic from the tip of the probe. At some point you'll get down to a shiny glass bead like this

You really only need to trim away 0.5mm from the tip. Mine looks ugly because I was trying different things like sanding wheels.*

A controversial topic, no doubt. But with the exception of the V1 designs, there haven't been any issues directly related to pulleys. Pulleys may or may not offer gains but they certainly improve response to throttle which makes the car funner to drive. They can be a bit pricey, so these can wait until later in your build. I recommend all 3 (crank, alt and water pump), but some tuners have seen gains with only the alternator and water pump (please note I have not seen direct proof). Others have shown gains, and you can find the info floating around the forums.

Ported Throttle Body
The size of the OEM TB is perfect, but the design needs a little help. Getting your TB ported (not bored) will improve airflow which can lead to gains. Since the TB is already oversized, there is no benefit to getting it bored out (plus it's more expensive).

But wait, everyone sees gains with the bored tb! Sure, because some of the design issues get solved during the bore process and also the stage in their build in which they added the TB. I've done back to back dyno testing of a BK2 3.8 full bore tb vs a ported tb and there was no difference at all and in fact, the ported tb still had more room to lean out AFRs for additional power over a bored TB. The biggest difference is the mid-range TQ will be better over the bored tb, but top-end will remain the same or slightly better.

Bored TB costs $125 + shipping and down time (or a core purchase) while a ported tb cost $75 and if you get it done by 3point8 Performance, you can take advantage of the core exchange program so you don't have any down time.

BK1 throttle bodies are even larger than BK2 and really don't need to be bored out, just cleaned up. While not part of this post, 2.0T guys are seeing great benefits with a ported TB.

PnP Manifolds
There is power to be had from working these manifolds for sure. BK2 manifolds need a little bit of love, cleaning up all the poor casting and fixing the port shapes while the BK1 has massive issues that need to be fixed. BK2 3.8 manifolds with my standard port job makes 8wtq and 6whp mid range without a tune and can help bring peak numbers into the 320's with custom tune and other supporting mods. One customer of mine made 327whp (beating my then record of 326).

BK1 has massive port matching issues that need to be fixed. The casts were some how offset on the runners

This photo shows a mild overlap. I thought I had more photos or worse overlaps, but I couldn't find them. There are some severe cases of 1/2" of overlap!!*

Not only that, BK1 runners have narrow openings inside the plenum on 3 of the runners, two on driver side and 1 on passenger side.

Most of the gains from porting are had in the curve more so than in the peak so it makes a big difference when you're driving around town and doing pulls with friends.

Porting vs Flow Balance
I often get asked if I have flow numbers for my port jobs. The answer is no, I don't. I don't need them. I have dyno results. The companies that were offering flow balance port jobs just hog out material enough to show balanced flow numbers on their flow bench. Just because they flow equally on the flow bench doesn't mean they'll make more power or actually be flow balanced at all. The way the flow balance port jobs work is to remove material until it flows equally across the runners, but they only consider CFM and don't consider velocity. If the non modified ports end up with better velocity then the other ports will not flow the same anyway. The factory design is fine, the problem is their execution and a good port job brings the manifold inline with the original design.*

Having done over 60 manifolds both BK1 and BK2, it's easy to see why they'd flow differently and those things can be fixed without sacrificing velocity. To-date no one with a flow balanced manifold has put down more power than any one of my customers.

Heat Shielding
Heat is a big problem for these engines. What no one realizes is that the stock airbox is actually a true cold air intake, but even it can get heat soaked. Adding heat shielding to it can reduce heat soak and improve recovery from heat soak.

It's easy to do and doesn't take long. Just wear gloves.

This is the best heat mod that you can do for the 3.8. Using a fast acting IAT sensor, I tested the temperatures inside of the manifold. Even with the phenolic spacer, at WOT (when the most amount of fresh air is coming in to the manifold) temperatures were pegged at 130*f while it was 80* outside. After applying heat shield to the underside of the upper intake manifold and testing again, I saw ambient temperatures inside of the manifold at WOT. Massive difference not only at WOT, but also in preventing heat soak in general which can result in more power, but more importantly consistency.

Remove your manifold, clean it with degreaser, then clean the underside with alcohol. Bake it in the over at 350* for 3 minutes to get it warm. Bake the heat shielding for 1m so the adhesive is very sticky. To make it easier, you'll want to pre-cut the heat shielding material before doing all this work. While hot, apply the heat shielding, smooth out any high spots and trim it as needed. Bake again for 4 minutes at 350*, then let it cool down. This will help the adhesive bond to the manifold. This is a $20 mod.

Phenolic Spacer
Don't bother. I know everyone wants to say "but I put my hand on the manifold and it was cold!!". It can certainly help slow down heat soak of the upper manifold by the lower manifold, but it's $60-$80 and and in my dyno tests, it shows a small loss of both hp and tq across the range (even when the manifolds are port matched). As far as helping the temps in the plenum, it isn't worth the cost (in my opinion).

Throttle Body Spacer
Throttle body spacers don't really add any power, but they are still beneficial. A TB spacer will increase the plenum volume which can improve the smoothness of shifts for MT's. The car will be better to drive around town. AT's won't notice it so much. Since most spacers come with an 1/8 NPT port, they can be used for meth injection, nitrous or for running a fast IAT sensor. Regardless of claims, you won't see anything power wise from a spacer that would not be considered normal variance from the dyno.

3point8 Performance
2,628 Posts
Discussion Starter #4
Ah, the most discussed topic ever. I'm not going to lie, it can be very difficult to get both performance AND sound quality, but it's doable. First, I need you to remember, bigger isn't better. It might sound like it makes sense, but trust me, bigger exhaust will hurt your performance when you're NA.

Do you even need them? Will you lose power? Will you make power? Will they be raspy? Which are the best? Lot of questions around headers. First, the stock exhaust manifolds can flow well enough. I made 326hp/290tq with mine. So, they are not "restrictive" as is commonly thought. The BK1 stock exhaust manifolds, however, need some modification. The exit of the BK2 stock exhaust manifolds are 2.25" which matches the size of the down pipes. BK1 exhaust manifolds, have a 2" exit going into a 2.25" down pipe. And it makes it worse when you're throwing on Ark down pipes that are 2.5". If you're crafty enough, you can expand the exit on the manifolds with them in the car which will save the hassle of removing them from the car.*

If you do choose headers, be aware they are not all the same. Ark and CNT headers have a 2.5" collector which is too big. They also both have very bad welds and are not put together with care. You can see my thread here about the differences between the CNT and the J2. Not only that, CNT has an issue with melting the driver side engine mount and the Ark headers are overly expensive.

NGM and Turbokits headers are designed to work with boosted applications and are way too big for NA setups.

So far, J2 headers are the best way to go for performance. They can sound raspy, but a little heat wrap fixes it. The collector is 2.30" which is much better for these engines and the build quality is much better (see the link above for reasons why).

Down pipes
Do they work? Are they worth it? Down pipes are an important part of the exhaust system. They determine where peak TQ occurs. I'll flat out tell you, the OEM down pipes ARE THE BEST! They are 2.25" while Ark and others are 2.5" (J2 is 2.30"). When you do the math, 2.25" is the best size for this motor because it matches with where the 3.8 can make peak tq. Moving to a 2.5" down pipe shifts the peak tq RPM higher in the rpm range where the motor cant actually make tq, so you're losing down low tq and sacraficing tq up-top and this is part of the reason guys are losing power with headers (because they often pair headers with down pipes).

A local BK1 with Ark headers and ark downpipes switched back to OEM downpipes at my recommendation and picked up 20wtq with custom tuning vs his previous setup with custom tuning.

Port the OEM down pipes
The OEM down pipes are the best option for NA performance, but that doesn't mean they don't have issues that need fixing. The weld bead on the inside of the pipes needs to be trimmed down as it can neck down from 2.25" to almost 2"!!

There is plenty of meat left, so you can get it all the way down and make it 2.25" again

Take a look at another thread I wrote up here: A look at Hyundai's sh*t QC

Test Pipes or H Pipe?
As far as I know, the only one who made an H pipe was Ark and there is no performance difference between the H pipe and test pipes. The Ark H pipe is too expensive and doesn't fit well at all. Avoid it. Test pipes will provide nice gains and nice sound when paired with a quality CBE. The Ark H pipe does change where drone occurs, but keep reading on how to fix that cheaper.

Cat Back Exhaust (CBE)
Yes, get one. That stock muffler sounds like crap. IMO the Ark GRiP V2 is the best sounding setup (though it's really expensive). You'll see gains with a decent cat back but the choice will come down to price and sound.

Straight Pipes
Avoid this. Not only does it sound like absolute garbage, you'll make less power.

Exhaust Rasp and Volume
A lot of rasp can be reduced by wrapping key parts of the exhaust, headers and down pipes. Wrapping also gives it a deeper tone as well. But for those who are full catless like I am, you need more than wrap. This is where a custom H cross over comes in.

Add in a 2" cross over on the OEM down pipes like this

It eliminates 99% of the rasp and will reduce the volume so when you're not trying to attract the cops, you don't have to worry about it. It also adds bass to the tone which is nice. It cost me $40 but depending on your shop, will be $40-$100. I've already had 3 guys locally and a few across the US who've done it they've each said it made a massive difference. It also adds a little mid range TQ which is nice too.

Check out this post for sound clips and comparisons: Quiet Exhaust with Headers?

3point8 Performance
2,628 Posts
Discussion Starter #5

No build is complete without a tune! Custom tunes are the best since they get the absolute most from your build, but you should only go this route once you've completed everything you need to do. Changing anything after a custom tune can ruin your numbers. If you just want some nice gains without the hassle and price, then grab a canned tune. It has all the features of a custom tune and it'll provide some gains, just not as much as a custom tune would.*

There seems to be a lot of unrealistic expectations. Then BEST you can hope for on this platform at this time is a 20-25whp gain from a custom tune. That's going to be the tops and it all depends on your setup. Please do not get upset if you don't get the numbers you were expecting.*

Which tuning company? Well, to be honest SFR knows these 3.8s well and consistently have cars putting down better numbers and better curves than the other guys. Based on fact, not opinion. BUT, sometimes you just have to go with what's available. BTR and Alphaspeed are options and there are new options appearing but while I love that they're trying to break into the market, I strongly encourage you to stick with well known, reputable tuners. I understand it's a catch 21, but better safe than sorry.*

TCU Tune
If you have an AT, you are in luck because tuners are now able to tune the TCU. The TCU is the ECU for the transmission. Tuning the transmission really changes the way the car behaves and makes it much more fun to drive and race. Other platforms have been enjoying this for years and while we don't yet have all of the features they do, at least it's getting there. Faster shifting, high rev limits are just some of the features we can get right now.*

Unfortunately, at the time of this writing, it's only doable with the car at the tuner's shop or at a tune event, but stay tuned because remote stuff is gaining traction!

Electric Vacuum Pump
A vacuum pump, in general, is an added benefit to any engine that is high performance enough to create a significant amount of blow-by. A vacuum pump will, in general, add some horse power, increase engine life, keep oil cleaner for longer.
A vacuum pump has the inlet hooked up to one or both valve covers. It SUCKS the air from the engine, thus reducing the air pressure build up created by blow due to combustion gases going past the piston rings into the pan. Vacuum pumps vary in the amount of air volume (CFM) they can suck so the potential VACUUM a pump can create is LIMITED by the amount of air it can flow (CFM). The exhaust from the vacuum pump is sent to a BREATHER tank with a filter on the top, which is intended to retain any fluids (moisture, unspent fuel, air born oil) sucked from the engine. Exhaust air goes to the atmosphere thru the air filter.
Essentially, a vacuum pump can help reduce drag on the crank which results in less power loss. Electric vacuum pumps have been criticized as not being strong enough to produce enough vacuum to be beneficial power wise, but they've also proven to be effective and plenty of manufacturers used them in high performance cars. Ford used one on the 98 Cobra and that it the one I put on my car. I bought one brand new from ebay for $130 and mounted it under the drive-side head light and set it up on a WOT switch.*

Unfortunately I did not get a chance to do before/after testing with it due to time constraints for the tune event, but whether it adds power or not, it has the added benefit of preventing sudden knock I get after I let off the throttle from a hard pull. With the pressure building in the crank case and then the sudden vacuum from the PCV, oil always finds its way into the intake and I get knock in one or two cylinders even with a catch can. With the vacuum pump, I have not seen this occur after many WOT pulls.

Additional benefits are to help the longevity of the oil by better removing contaminants and moisture in the blow by gasses.*

Better grounding
Electronics are what control these cars and the electronics depend on electricity. Hyundai did a crap job on setting up grounding. Doing the big 3 or even just doing the better ground mod can make a big difference. Doing the ground mod I gained .5v which might not seem like much, but to the ECU it's massive.*

Without a solid electrical system, sensor data can change which causes your tune to change (stock tune or custom tunes alike). The ECU times injector pulses and ignition charges based on system voltage. Injectors are solenoids and require power to move them. When you're at 7000 RPM there is very little time for that solenoid to open and close, so if it doesn't have the proper power that it needs, problems can occur, from power loss to issues with fuel pooling. The ignition coils need time to charge before firing off and again, at 7000 RPM that time is very limited so having the proper voltage is crucial to a high performance application and can make or break a tune.

Not only that, but head lights won't dim when the stereo is playing (especially if you have an AMP), there is less stress on the other electronics and the car will start faster.*

Coolant Bypass
This mod reduces the intake air temperatures. It's common for cars from the factory to run coolant through/around the throttle body. This is done not to cool it down, but to heat it up. There are a few reasons like better emissions, prevent freezing, etc. But if you live in an area that is warm or hot most of the time, then what this setup does it increase air temps going into the motor. Hotter intake temps mean less timing and on our motors, timing is everything.*

This is a very simple mod. I actually spent $5 to get a new length of hose, so it wasn't totally free for me, but you can do it without spending any money.*

You can see the data from the tests I performed here: Coolant Bypass Data

Head work
There is really no way to break out of the ~320whp range without head work. The heads need to be ported in order to see more gains. A full port can be expensive and requires you to remove your heads. But if you have the time and money, a stage 1 port job (cleaning up all the casting imperfections), a radius valve job and adding a larger exhaust valve can result in big gains. If you don't want to go that route, you can get some porting done to the intake ports with the heads on the car. While I'm building my performance heads, I did a stage 0.5 port job on my current heads while on the car. Just like the intake manifolds, the heads need clean up of the poor casting and fixing some manufacturing problems.

Look at this junk!

Basic clean up like that might nor result in massive gains, but it can really help smooth out the power band and make the car safer.

The next piece is the fix the casting seams along the walls. The just need to be reduced down a bit, nothing crazy. Then the port divider can be smoothed out. It doesn't need to be knife-edged, but the geometry needs to be smoothed out to reduce the amount of turbulence. This change made some nice gains up top.

IMO I believe with proper head porting and valves, 350whp is doable.

Please note that I don't recommend anyone doing this unless they are really experienced. You take out too much material or change the geometry incorrectly and you'll hurt performance all over. It's also dangerous to do any port work with the components installed on the car. Metal shavings and get into the valve seals, cylinders, coolant and oil and cause problems.

Also note that this port design may have been intended to purposely cause turbulence on BK1 to help mix the air and fuel. I believe this to be the case and I think that the design just carried over to BK2 for convenience so it may hurt BK1 more than it helps. I have no data to suggest either, so just wanted to make you aware.**

Valve train
One of the things that Hyundai did with the BK2 was to lighten the valve train components. BK1 has a lot of room here so install springs and retainers which are much lighter. This will show nice gains across the entire range. This route is a little more expensive (~$800), but if you're looking for all the power you can get, then it's an option. You can do this for BK2 as well, but the gains will be much much less and should only be done if you're already doing a full head build.*

At this point in time, I only know of 1 guy who has done cams for BK1 and he made 325 (so gains of 20-25whp). No one has yet done BK2. Cams are a very expensive option ($1200 plus cost of cams and any labor). Once you have the cams, you have to have someone who can tune them and it has to be a custom tune.

Bisimoto can do the cam re-grind. It's about $300-$500 per cam depending on the company you go with and it's 4 cams which is why it's expensive. There are a few other companies who will do work on DOHC shafts, but they are more expensive, ranging up to $2,000.

The problem with the cams is how it shifts the power band up so you have to rev out the engine more to get that power and that's just not safe for these engines. There are other ways to get more power, cheaper and safer.

Meth Injection
There are no gains to be had here for BK2. It's been tested. You'd need 100% M5 to see any gains (they'll be small) and running 100% meth is dangerous not only for your engine but also your safety. When running 100% it tends to destroy your oil far faster than normal due to blow-by, so you have to change it very often. If you happen to have a leak and the meth catches fire, it burns hot and it's invisible so you can't see the flames.

a 50/50 mix is much safer and BK1's have seen some gains, but they're not much to talk about (not worth the cost IMO). If you apply the heat mods I mentioned above, there is nothing gained by cooling the IATs either. There are gains going from 140* to 100*, but nothing to gain from from 100* down to 50*.*

If you're going with a nitrous or boosted setup, meth is a good safety measure, but NA it's just about pointless unless you have a non power related reason to use it.

3point8 Performance
2,628 Posts
Discussion Starter #6 (Edited)

3.91 Final Drive
For you BK1 and BK2 3.8 MT guys, and BK1 3.8 AT guys, doing the 3.91 ring and pinion swap is one of the best bang for the buck mods you can do. It dramatically improves acceleration and how the car feels. It pulls harder in every gear across the entire RPM range regardless of tune. Read more about the swap here: [Review] 3.55 -> 3.91 Gear Swap.

You should be able to get every thing purchased and installed for $650 or less and will be the best mod you've ever done. Some guys have tried the 4.18 ring and pinion, but for me that's too aggressive because I like to drive on the highway for long distances. If you're a hard core street racer or like the 1/8 mile, then it might be a good option for you. I've spoken to a few BK1 owners who did the 4.18 and they love it and DD their setups. They do say that 1st is almost useless which would be something to consider but again.

Going with a lower gear ratio (numerically higher) increases the torque multiplication. For the 3.55 to 3.91 it's a 10% reduction which means it's the same as adding +25wtq across the entire RPM range.

Expect higher oil temps and worse fuel mileage. 3.55 -> 3.91 = 3300 RPM @ 80mph 3.55 -> 4.18 = 3500 RPM @ 80mph. If you go with a 4.18 I recommend getting an oil cooler.

Sprint booster
Yes, you can get a 1:1 tune and yes it improves the throttle response. No, it is not the same as a sprint booster. The sprint booster is adjustable and can make the throttle far more sensitive which can make for some fun driving. It doesn't necessarily change your power curve but it makes the car feel so much faster. It has handy features as well, like Eco or Valet mode which significantly reduces throttle input if you let someone move your car, or you want to drive up some ramps.

Yes, it works with tunes and yes it does make a difference. Anyone who says it doesn't make a difference with a tune didn't set it up right. A cheaper option is the Tross Potent Booster (which is what I have). It's about $120 vs $300 and it works the same and the install is like 10 minutes.*

Engine Leash
The stock engine mounts are very soft. My guess is Hyundai made them so soft for the comfort of the driver since their target market wasn't hard core drivers. These soft mounts can make response to throttle seem sluggish as it take a noticeable amount of time before the power is delivered to the wheels after you press the throttle. You can solve this with solid engine mounts, but there are problems with this approach. They can be expensive (if they exist), hard for the average person to install and they add a lot of NVH which most people won't care for. You can poly fill, but it's the same idea and results.

The engine leash fixes this by preventing the engine from twisting which vastly improves the response to throttle (not throttle response) as the power gets to the wheels* quicker and there is absolutely no NVH with the engine leash. Over 200 of them have been sold and they are a favorite first mod because it makes such a big difference in how the car drives. It can fix missed shifts during hard acceleration.

Megan Trans Mount
An easy to install mod that replaces the wonky OEM mount. This stiffens up the drive-train and can help eliminate missed shifts and prevent wheel hop. This too is a common popular favorite mod.

Shifter Bushings
The stock bushings can get replaced with some stiffer ones which can improve the feel of the shifts.*

Short Throw Shifter
Honestly, I don't think this is worth the money or related problems. It doesn't actually help you shift faster; any time you save is negligible at best and it doesn't address slowness in other areas. A lot of people go back to stock shifter and are much happier.*

I do like the "clunk" feel when putting it into a gear, but the shift knob is either freezing or scolding hot, it heat soaks while driving and it rattles.*

Brake Pads
No point in going fast if you can't stop. OEM pads are the absolute worst! EBC Reds are nice replacements for street driving and EBC yellows are absolute awesome pads. They're a bit pricey, but well worth it when you're needing to stop on a dime. OEM pads fade with normal stop and go traffic, but performance pads can deliver results. Of course, there are other pads out there as well, do your research.

Brake Lines
These are more for the track oriented/canyon run driver. The OEM rubber lines are plenty strong, but they can get soft with enough heat which can cause brake pressure drops and that means you won't be stopping like you want. Stainless braided lines will keep the rubber lines from expanding under high heat braking scenarios. I've encountered this issue and it's scary.*

Brake Fluid
Again, for the track oriented/canyon run drivers. The normal brake fluid will over heat (even before the lines) and let me tell you having that happen is much scarier than the lines expanding!! I've run Castrol SRF and it's amazing. It's super high temperature that won't let you down lap after lap. It's a bit expensive ($70 per bottle), but worth it when you need the best.

Whiteline Front Sway Bar
Thicker than even the OEM R-Spec front sway bar, it aids in stabilizing the front end on un-even surfaces at high speeds and can help reduce understeer in high speed turns or sudden high speed lane changes. I have not been back to the track since adding this, but doing freeway pulls at high speed can be super scary when it suddenly becomes uneven. The r-spec sway bar was better than the base model sway bar, but the whiteline improves on it even more giving you a sense of security in those scenarios.

Wheels and Tires
The factory bridgestone tires are not that great at grip and they are heavy. I highly recommend getting new tires. Most of the tires I looked at were lighter in weight. Shaving a few lbs per tire will have noticeable improvements with regard to acceleration. If you're running the factory 19" wheels, you should also get a wider tire. My setup is 235/35/19 in the front and 255/35/19 in the rear. The extra width will help with grip as long as you don't get cheap'o tires.

Lightweight driveshaft
This is an option that can help the engine rev quicker and will cut some weight. It's an expensive option though and personally I don't believe the benefits are worth the cost. Some people have had issues with theirs and others have not had any issues at all. Just do your research and make an educated decision if you're considering this option.

Lightweight flywheel
This is a mod I'd recommend for the race driver who wants everything from the car. Lightweight flywheels can improve engine response by allowing it to rev faster and it reduces rotational mass. The down sides can be noisy clutch chatter and harsh drivability along with bad manners in stop/go traffic. Hyundai used a DMF (dual mass flywheel) for comfort.*

Weight Reduction
These cars respond very well to weight reduction! I've seen stripped down gens keep up with and even beat higher power cars out at late night races. Weight reduction can be a tricky (and expensive) area to tackle but it's worth the effort. I won't list everything or what the actual reduction will be but instead just the items that you should consider.

1. Tires
2. Wheels
3. Hood
4. Trunk
5. Spare Tire (Can be removed when racing)
6. Washer fluid reservoir (already removed because you got a true CAI, right??)
7. Rear seats (this adds a LOT of additional noise)
8. Trunk rubber mat. This thing has to weigh 20lbs I swear.*

3point8 Performance
2,628 Posts
Discussion Starter #7
Power Adders

If you haven't seen any of @shorttracks threads on his nitrous build, then go do it. I'll sum it all up by saying that for $600 - $1200 (depending on what you get) you can add 50-75whp safely. The best part is that it's not always on, but it's ready to go when you want that extra boost.

The 3.8s can handle a 50 shot no problem (assuming a healthy motor) and based on @shorttracks testing a 75 shot is fine. These have to be wet shots, of course, not dry.

This is the route I'll be going eventually. I have the N2O kit already but I'm waiting to get a NANO system before I do any installation. For me I love my car as is, but for those times when I think I'm going to lose a pull, I want that extra power on tap.

Turbo Kits
The most effective way to increase your power output will be a turbo kit, hands down. a 3.8T is a force to be reckoned with for sure and you can get between 380 and 480 whp with a kit depending on the route you take. If you want serious power then you will certainly need to build the bottom end. Thankfully we have an awesome engine builder who loves this platform @GenCoupe13. You can see his NA build thread (kind of old) here: Before and After Dyno's from Stock 13' 3.8. He has built some amazing motors from a 4.2TT to the engine in BTR's SEMA car and just did @Vacmurse 4.2T motor.

There are more and more 3.8T builds every month and a lot more guys learning how to push the limits. I'm sure you've seen the red genesis that made over 600whp. It takes a lot of work, time and money, but it's doable. You can't take any short cuts though.

Stroker Kits
If you want more power, but want to stay NA, then a stroker kit might be for you. The kit takes the engine from 3.8L to 4.2L and again, @GenCoupe13 can help get it all done. This kit adds around 50whp (advertised) and I can't recall what the torque gains are, but increasing displacement always increases torque.*

The 3.8 is such an awesome car. It looks great, it feels great and it's fun to drive. There are a lot of gains to be hand from simple clean up work that Hyundai felt was unimportant or just tried to cut costs. There are others like me who want to move this platform forward and spend their time working on new ways to get power, testing and tweaking. Please give respect to them and show your appreciation for their hard work and efforts.

I didn't include absolutely everything and I may not have gone into extreme details, but this is enough to get you to the point of a good build that makes you happy. Enjoy!

'13 3.8 Track
858 Posts
Good write's been awhile since I've posted here, but last July I had a BTR custom tune and the AT Tune. I have done many of the mods you call out here, but have stopped short of porting/polishing. No nitrous or FI. But, my 8 speed A/T made 302 WHP in the California heat. I watched several other 13+ GC's make quite a bit less. One guy looked super bummed when his 2014 manual only made 282 WHP.

Anyway, just a data point to say that these mods to work. :)
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3point8 Performance
2,628 Posts
Discussion Starter #9
Good write's been awhile since I've posted here, but last July I had a BTR custom tune and the AT Tune. I have done many of the mods you call out here, but have stopped short of porting/polishing. No nitrous or FI. But, my 8 speed A/T made 302 WHP in the California heat. I watched several other 13+ GC's make quite a bit less. One guy looked super bummed when his 2014 manual only made 282 WHP.

Anyway, just a data point to say that these mods to work. :)
Yeah, there are a couple of "evo" dynos here in SoCal that are setup really low so some guys are seeing like 250-285 and they get bummed out because they don't know that the dyno is setup wrong. I learned a lot from the guys who own/run Import Auto Pros about not only their dyno, but some of the other places in SoCal as well.

Where in Cali are you? I'm in the San Bernardino area.

'13 3.8 Track
858 Posts
I used to live in Thousand Oaks, but I moved to Boise, ID about 10 years ago. I went to Sacramento (area) for the BTR tune last July...drove 8 hours just for that! Was worth it, though...I had a "problem" with my canned tune that could've been fatal to my engine.

9 Posts
Aaaaand SUBBED!

Damn good write up, sir. I still have yet to tackle a few of these things, but I'm well on my way.

For the intake mod, what did you end up doing with all this nonsense up here? ^^

3point8 Performance
2,628 Posts
Discussion Starter #12
Aaaaand SUBBED!

Damn good write up, sir. I still have yet to tackle a few of these things, but I'm well on my way.

For the intake mod, what did you end up doing with all this nonsense up here? ^^

For the sound tube I just removed it so it's out of the way. Some people cap it off, but I just left it exposed.
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22 Posts
Subbed again. For what it's worth, if you want to control temps in specific structures, ceramic coatings REALLY work.

1,209 Posts
See this is what the community needs alot more of. More people like Titan with a methodical approach to everything they do. He just put basically 4 years of trial and error (plus the years of work of others before him) and thousands of dollars of time and work in a single forum thread for all of us to reference and learn from at the click of a button. And his work is proven without a doubt. I was stoked to be there the other day to see all that hard work come to life on the dyno and pick his brain a little bit too ?

Best thing in this post is the comment about building the car for what works for you. Dont focus on the BIG numbers just focus on what you want. Then use these guides he and others have put together to polish it all off.

In Charge of Snacks
2,109 Posts
Well done, Dusty! Throw in a few more curse words and a sprinkling of racial epithets and even Ol' Jimbo would be proud.

3point8 Performance
2,628 Posts
Discussion Starter #16
See this is what the community needs alot more of. More people like Titan with a methodical approach to everything they do. He just put basically 4 years of trial and error (plus the years of work of others before him) and thousands of dollars of time and work in a single forum thread for all of us to reference and learn from at the click of a button. And his work is proven without a doubt. I was stoked to be there the other day to see all that hard work come to life on the dyno and pick his brain a little bit too ?

Best thing in this post is the comment about building the car for what works for you. Dont focus on the BIG numbers just focus on what you want. Then use these guides he and others have put together to polish it all off.
I'm hoping someone can take this and run with it and come back with even better output. I just want to show that with some effort, it's possible. And you made me realize I didn't give credit appropriately. I did learn from a lot of people in this community as well as other communities/platforms, and I also used a few ideas from others as a launch pad. While building your car is a personal effort, building the platform is a community effort.

Well done, Dusty! Throw in a few more curse words and a sprinkling of racial epithets and even Ol' Jimbo would be proud.
lol, I keep all those in the garage and directed toward the car. I believe cussing and belittling the car is an important part of the build :grin:

3point8 Performance
2,628 Posts
Discussion Starter #20
Titan what's the most important things to do when a just wants to cruise?.

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Some cool shades and a tasty beverage. IMO just doing the 3.91 swap and an engine leash with no other mods would completely change a stock 3.8 into a very fun cruiser/canyon runner.

I'm sorry titan 2782 sir

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