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test pipes... h pipes... x pipe... the decision approaches

14K views 47 replies 9 participants last post by  shorttrack 
#1 ·
I'm going to throw the free and low buck mods on my car from Titan's list. As part of that, I want to install the test pipes. My brain says "get H pipes", but I've also seen posts here that say the H pipes are not the way to go. What is the current skinny on this?

Also, is anyone making an X pipe? I know Magnaflow has that as part of their system. But what about a direct bolt-in for the stock exhaust? Or are the pipes too far apart for a practical X?
 
#2 ·
X pipe,Summit racing.Not the stamp steel ones.Make more power and noise .
 
#5 ·
Wanted to keep my exhaust all stainless steel because I use water/meth while using nitrous .Instead of using test pipes (drone and too damn loud) I used vibrant resonators that I welded flanges in the same length as secondary cats and flange face bolt pattern also the same as cats (direct bolt in place) .Free flow design without the loudness .
 
#7 ·
Had pic's posted and 3rd party host took them down .I only send by phone direct with members that PM me with their tele number.It is easier that way .
 
#8 ·
X pipe point was placed in the only location available behind the Vibrant resonators /in front of the diff.
 
#10 ·
I wonder what happens when you have both, h pipe and x pipe.
I do, only because h pipe in place of secondary cats deals better with rasp. Folowed by magnaflow exhaust that had x pipe

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#35 ·
X pipe scavenges and make a little more than a H pipe .I do mean a little,like 1 to 2 hp more than a H pipe .
 
#12 ·
Didn't read all of the responses, but I'll just chime in with my experience.

1) Test pipes and H-pipe are both great options for replacing the stock cats and will get you great results!
2) Sound difference between test pipes and H pipe is NOT noticeable when using the Ark GRiP V2 CBE
3) The Ark H-Pipe and the Ark GRiP CBE do not fit well together at all!

Here is a photo I took of my trying to get the h pipe installed. Sure, you can install it as is, but it's tight to get the bolts in AND the openings don't line up, so you have a big overlap which DOES impede flow and will mostly negate any gains you would have gotten otherwise. I ratchet strapped the CBE to get them inline with the h pipe, then installed the bolts and torqued them down.



4) I have an exhaust leak with the h pipe. Because of poor fitment (whatever the reason may be) the OEM gaskets do not fill the gap on one end of each pipe so on cold start up you can hear the leak. Once warm, it goes away mostly. This could be remedied by using thicker aftermarket gaskets, but after having a set get blown out after only 3 months, I am not in a rush to redo the h pipe.

5) After switching to the h pipe, I do notice a bit more pull down low and mid-range. Butt dyno only, and I'll be going back to a real dyno again soon, but the tires now spin super easy on a low roll where as before they would grip unless I really ripped on it. So that's good.

Test pipes can be had for $100 used and $140 shipped from depot racing. The H pipe is a bit more expensive, comes with more hassle and is advertised by Ark to NOT work with other cat-back systems. If I were to do it again, I'd get a set of test pipes, get them installed and then have someone weld in a cross over.

Either way you'll be happy with the final result, but the journey is what differs.

Edit: I forgot the drone. With the test pipes, I had a massive drone on cold start while in my garage. So much that it would hurt my head. Just loud af! The H-pipe fixed that, but now, when hot and sitting idle, like at a stop light, I have a pulsing drone which isn't as annoying as the test pipes, but makes me look around like, "wtf is that"? It sounds like someone is bumping their stereo, but it's not, it's the H pipe. Driving is fine. I never had any drone while driving with either setup.
 
#21 ·
The H-pipe fixed that, but now, when hot and sitting idle, like at a stop light, I have a pulsing drone which isn't as annoying as the test pipes, but makes me look around like, "wtf is that"? It sounds like someone is bumping their stereo, but it's not, it's the H pipe. Driving is fine. I never had any drone while driving with either setup.
Let me guess: you can feel it more than you hear it?

If so, its my best guess that you have two conflicting wave fronts present in your system (from the air filter to the muffler tips). The difference between the two produces a frequency following response which your body perceives as a bass frequency - an infrasonic wave.

Generally, modern cars have extensive work done by the exhaust contractor (OEMs rarely do their own work, aside from matching the exhaust to the desired power band), as well as in-house stuff on the intake side, to ensure that this doesn't happen in showroom vehicles. You, OTOH, have changed more than a couple of things..:grin:

What would be really cool is if you could tune it in some way to produce between 17 and 18 Hz, which is the anxiety range. Then you could work up some wave guides, project it to the cars around you in traffic... >:D
 
#13 ·
My first question would be what kind of exhaust is this going with?? Custom exhaust?
 
#16 ·
No, this is going on the stock exhaust.


I appreciate the responses, guys, but I think some are overthinking this. I doubt I'll ever do a catback on this machine, because personally I like the the stock exhaust tone. When I eliminate the cabin sound connector I may rethink that, but for now its fine.

I'd like to eliminate as much of the back pressure as I can, so I'm looking at doing an H pipe on the factory exhaust. I see they're under $200 if you can find them, but I recall reading a thread here - and of course I can't find it - where someone mentioned in passing that the H pipe was not the way to go for best results. Meaning, the power gains weren't there compared to straight test pipes. I personally can't see that, because an H always gives a bank to bank pulse benefit and should improve low end torque on a good OEM street motor, which we have in the BK2.

As I mentioned in my first post, I'm going to work my way through Titan's list and knock out all the free/low buck mods. The exhaust is part of that. At the end, I'll have it tuned, if one of our two illustrious tuners make their way to my state.
 
#15 ·
For H pipe to fit, it needs to be installed on exhaust, transission cut and welded in flex bellow.


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#17 ·
What????????????????? The OEM muffler is a flow robber .If keeping in place you are wasting $$$$$$$$$ installing test pipes and or H/X pipe.Your cash and common sense , blow it away anyway you can, I mean want .
 
#18 ·
Your OEM exhaust system already joins the 2 banks into 1 ,why would you need a X or H pipe anyway when it will be joined back into 1 pipe before the main OEM junk muffler.You need to get a basic understanding of exhaust systems range of function.
 
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#19 ·
1). I didn't know that it was joined. I have yet to crawl under the car for any reason since I got it. Its been parked in my garage since I bought it and I put about 70 miles a month on it. The only undercar pic I saw so far was Strange's shot from when he mocked up his Spintech experiment, and that had dual pipes. I didn't even notice it had twin straight-throughs on it until now, because I was looking at the pipes themselves:



2). Go read my destruction of the backpressure myth . I know more than the average potato about exhaust.

My question stems from that thread I mention, where someone said the H pipes didn't work as well as the separates. That flies in the face of everything I know, but these cars don't seem to react well to the rules, evidenced by the people who have reported losses when they went to long tube headers. As long as you balance the intake side and retune, you should see gains. People have reported losses here.

As far as the back box - I always start at the front of the car and work back when it comes to exhaust. Headers and cat delete (or cat reduction, either by dropping one pair of cats out of two, or going to low cpi cats) is where the significant gains are to be found in the exhaust system. The last thing I think about is the muffler. On performance cars, they generally flow pretty well from the factory, and all those cats and manifold deficiencies up front rob a major piece of the tonal info that the stock mufflers could use to make better sound, and if you do change out the muffler, having the headpipe work done already means your new box has more to work with as well.
Perhaps I'm biased from all the years of watching people swap out mufflers on new cars and thinking they're gathering major power, but just ending up spending money on noise.
 
#20 ·
Shorttrack is 100% correct. If keeping all exhaust stock, why are you bothering to add x,h and/or test pipes?

If money is an issue, you dont need to get ARK but go with a quality aftermarket exhaust (including muffler), whether it be cat back or total removing cats.

Upgrading and improving (opening up) the intake and exhaust are the initial two best mods to make.
 
#22 ·
Shorttrack is 100% correct. If keeping all exhaust stock, why are you bothering to add x,h and/or test pipes?
Because, I'm working off Titan's list of free/low buck mods. This is all stuff that gives a little bump for minimal investment, and its all easily reversible for the most part. As I said in my last post, cats need to go. I'm not going to change out the entire exhaust to replace the cats with test pipes.

If money is an issue, you dont need to get ARK but go with a quality aftermarket exhaust (including muffler), whether it be cat back or total removing cats.
Money isn't the issue. Smart money is the issue. A muffler isn't going to change much except help others who paid money for the same thing feel better. That stings, but its largely true. A decent exhaust for this thing is over $1000.
Before I'd blow $1000 or more on some kit exhaust, I'd go do the Ferrari muffler mod, or something like that. I'd have a complete setup, custom, and still have a few hundred left. If I really felt like it, I'd cut open the box and de-baffle it, and save a ton of money. I have no interest in going crazy with this car on mods. I was going to pick up some coilovers, but the two decent options out there are around $1500. I have three other vehicles here I could throw money at rather than blow that much money on a car thats still under warranty. One of those rides is over 500rwhp, and way more deserving of the cash and attention.

I dig my Genesis, but its a once a month ride that I just want to add a little character to, not throw away money on a muffler.

Upgrading and improving (opening up) the intake and exhaust are the initial two best mods to make.
Weird... isn't that just what I said in my last post?
 
#23 · (Edited)
Hmmm...if you know so much than why are you posting? If you know so much than why go off someone else's list?

When upgrading the exhaust, junking the stock muffler is more than wasting money. The stock muffler is junk. Keeping the stock exhaust and adding just a x, h and/or test pipe is a waste of money.

Are you trying to change/improve performance or noise?

From your comments, not really sure what you are trying to accomplish...
 
#27 ·
Hmmm...if you know so much than why are you posting? If you know so much than why go off someone else's list?
I can't believe I'm even answering this, but I figure, what the hell why not?

Titan put in the long hours figuring out the first twenty mods or so on the BK2 3.8. After reading hundreds of his posts I'm a little bit past satisfied that he's done the due diligence. Every question that popped up in my mind as he went through his list, he answered before I could ask it.

Should I reinvent the wheel? Or just go take a look at what wheels other guys choose?

Now as to why I'm asking the question, please refer to my original post. I'll summarize here, and add some detail: I want to take out the cats. I want to put pipes where the cats were. I would put in an H pipe, yet somewhere in my studies here on the forum, I found at least one person who said that straight pipes were better than H pipes. That violates the rules for a bank-to-bank exhaust, but sometimes things don't play by the rules. So I wanted to know if anyone had any more information.

At this point, I'm kind of sorry I asked in an open thread. I should have just PM'd Titan, but I bet he's about tired of getting questions by now.

When upgrading the exhaust, junking the stock muffler is more than wasting money. The stock muffler is junk. Keeping the stock exhaust and adding just a x, h and/or test pipe is a waste of money.
I keep forgetting this exhaust necks down to a single entrance muffler. Honestly. I will be replacing the muffler, but I'm not going to waste $1000+ on it. I've already picked out what I'm going to use and I'll probably come in at $750 or less, installed.

As far as replacing the cats with test pipes being a waste of money - no its not. It never is. As long as your ECM/ECU whatever can compensate without needing a tune, its not a waste of money. You will always pick up power doing it. Even changing from the high cpi factory cats to low cpi aftermarket cats can bring up power. As long as your ECM can meter the fuel, and your intake side has the air to balance it, it works.

Are you trying to change/improve performance or noise?
I'll put my priorities in a list form, for future reference:

1). Performance

2). Sound


From your comments, not really sure what you are trying to accomplish...
I gathered that.
 
#25 ·
Archive you purchase a car and never look at ''YOUR'' car's exhaust system you want to mod is something a person of less than the average potato would do concerning exhaust performance up grades of any sort .Do as you wish but find out what is truly needed to meet your goals of any up grades concerning your car .Most of all ,if dialog is put across a somewhat gear head forum in the form of a question ,at least understand what you are asking .
 
#30 ·
I'm pretty clear on what I'm asking. Its everyone else I need to worry about. :grin:


Seriously though - I just wanted to find out what the last word has been about straight vs H pipes, and maybe see if anyone has done an X outside of the Magnaflow kit. Somehow it gets turned into an inquest into my motives, and people pull out their version of exhaust 101.
 
#26 ·
Total waste of money if you keep the stock exhaust
 
#32 ·
unfortunately no one has done a test pipe vs h-pipe dyno run (i will be pretty soon actually), so not much detail there. If you look around, most people believe that the benefits of the cross overs are lost on our engines because of the even firing order. In the american V8's with the unequal firing order, the cross over helps to equalize the pulses (read: scavenging) and it also helps makes it sound better because of the equalizing of the pulses. Since our engines have the even firing order (bank 1, bank 2, bank 1, bank 2, bank 1, bank 2), supposedly the cross over isn't as helpful.

However, I'm not so sure I'm buying that, I'm no fluid dynamics expert, but it still seems that the pulse from each bank could still be improved by the cross over regardless of firing order and a slight scavenging advantage can still be had. Will be it as significant as it would be on a V8? Maybe not.

Either way, no matter what you go with, removing the cats will provide some benefit. But obviously adding a CBE (be it dual pipes or a larger single exit) would maximize that benefit.

Edit: And actually, if you think about it, the H pipe will be ineffective at higher RPMs, so effectively it becomes just test pipes as the exhaust is traveling too fast to take advantage of the cross over.
 
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#34 ·
unfortunately no one has done a test pipe vs h-pipe dyno run (i will be pretty soon actually), so not much detail there. If you look around, most people believe that the benefits of the cross overs are lost on our engines because of the even firing order.
Thats one of those "on paper" rebuttals. People who say that don't understand that every motor develops exhaust harmonics of various orders that can take advantage of crossovers. Its the crossover design and placement thats up for debate.

In the american V8's with the unequal firing order, the cross over helps to equalize the pulses (read: scavenging) and it also helps makes it sound better because of the equalizing of the pulses. Since our engines have the even firing order (bank 1, bank 2, bank 1, bank 2, bank 1, bank 2), supposedly the cross over isn't as helpful.
That seems logical on its surface, but it doesn't explain why inline six motors with two sequential "banks" of cylinders can still benefit from a crossover - if its properly located.

Ultimately, a crossover is no different than a primary merge for two cylinders. The precise location of the merge should be where the heat value of the exhaust charge drops enough to affect velocity. Thats where the "long tube" concept has its roots (that, and the need to exploit the harmonic that travels back up the pipe after each ignition event to boost scavenging, and - believe it or not - tune the intake charge). The header collector is located precisely where additional chamber volume is needed to help boost velocity. When you crossover two collected banks, the balance has to be located where the velocity drops below a certain threshold.


However, I'm not so sure I'm buying that, I'm no fluid dynamics expert, but it still seems that the pulse from each bank could still be improved by the cross over regardless of firing order and a slight scavenging advantage can still be had. Will be it as significant as it would be on a V8? Maybe not. Either way, no matter what you go with, removing the cats will provide some benefit. But obviously adding a CBE (be it dual pipes or a larger single exit) would maximize that benefit.
You're correct on both statements.

Most factory performance models have free flowing mufflers, and simply need a cat delete and perhaps headers to get the most out of them. In the case of the 3.8, the proper way to do it would have been to have two separate bank chambers inside that back box and use a dual inlet. I can't imagine what the inside of that thing looks like - that huge muffler, but a single inlet? If Hyundai wanted to use a single inlet they could have had something half that size on there and gone with a single exit, but of course it wouldn't have sold well in the American market, where people expect dual/quad tips. Not that these cars sold well here to begin with...

Edit: And actually, if you think about it, the H pipe will be ineffective at higher RPMs, so effectively it becomes just test pipes as the exhaust is traveling too fast to take advantage of the cross over.
Thats a good observation, and one of the reasons the rule of thumb has been "H pipe for torque down low, X pipe for hp up high". The H balances pulses at low RPM when volume (air mass) is lower, the X picks up velocity when volume increases. But, while fluid dynamics certainly applies here - and its really the dominant discipline - acoustics also plays a large role. For all the talk of the air mass and how the exhaust can help the flow, you have to be concerned about standing waves and phase changes as well. (Its one of the reasons why I am suspicious of the stamped style X merges, which cross the banks at nearly a 90 degree angle. I like the siamesed X merge a lot better.) If there are harmonics in the exhaust that can take advantage of an H pipe, it will still work even if you aren't getting significant flow across the H.

The irony is that the X/H crossover isn't necessary if you design an exhaust strictly according to fluid dynamics. You always merge:
1). when velocity drops enough
2). when pipe diameter needs to increase to manage increased air mass. This holds true whether you're talking about a primary merge or a bank merge.

I think the biggest tradeoff in the exhaust is after that bank merge (primary collection plays its own game, and its one of the most fascinating areas of exhaust design). On paper, the best thing to do would be to merge banks to a single pipe - again, at the exact location where velocity requires it - and then on to the muffler. That presents a whole bunch of other issues, most notably, what do you do when the air mass involved requires a pipe cross section that is too large to work with? You can either flatten the pipe, like a Dr. Gas boom tube, or you split after the merge into smaller pipes. Also, since these are street vehicles that spend most of their time on the lower half of the tach (unless its mine, and then expect to get criticized here for driving at 4k rpm - note the gauge in my avatar), that single large pipe isn't going to give the best benefit at low rpm, where a street car spends most of its time, so, you split after the merge.

And then we end up having these threads..:grin:
 
#33 ·
Yes H pipe is only effective at low rpms, while X pipe high rpms.

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#37 ·
@shorttrack I meant with the genesis. I've seen all the videos out there, but they are all for V8s. On our cars it comes down to sound only.

Adding in my custom H pipe made a massive difference in the sound with headers and test pipes. (please ignore the ark H pipe, that was only there temporarily as a jig).



Again, I've heard so many different setups and almost every combination results in a nasty rasp and is overly loud. My H pipe (2" diameter about ~20" long) removes 99% of the rasp and helps keep volume from getting out of control. I hear a slight rasp, but I believe it's just my heat shield vibrating or a leaking exhaust gasket. Will confirm later.

So, H vs X on this car isn't going to do anything except change the sound and an X pipe won't help rasp much (if at all). Both are a better option than straight pipe though. I've seen a few straight pipe setups and they come in lower than they should on the dyno. The biggest problem on this car is placement of a cross over. The Ark H pipe is too small and in the wrong place to make much difference. Most CBE come with an X, but it's pretty far down the line to be effective.

Your best bet is to figure out how to use the down pipes to fit a cross over.
 
#38 · (Edited)
I gained just over 1 hp from mid to red line (NA motor) but dropped 1/2 ft-lbs TQ below 4,375 . From 4,375 rpm's to red line my TQ went up by 2 ft-lbs with my X pipe vs my old H pipe ,not much .H pipe loses equalizing exhaust function at higher RPM's/HP .
Below 350 whp a H pipe is just as good a X pipe , the X pipe scavenge very well , I use nitrous so I need to make sure all of exhaust is expelled out during Nitrous runs and the X pipe does it's part by scavenging very well .
 
#39 ·
Been a while since anyone posted on this thread but maybe yall can be of assistance. Im looking to replace my mid resonator with an h pipe on my CNT V3 on my 3.8. I want to maintain a deep tone and not too loud (just need to get rid of the resonator for clearance issues). Is there a big sound difference between the h , x and cnt mid resonator?
 
#40 ·
OBX exhaust sells resonators ,look them up or you can make your own .Plenty of threaded info about the VIBRANT resonators I have made and others .
 
#42 ·
Get proper exhaust, muffler and resonator delete has no additional gain compared to aftermarket exhaust, but will sound horrible.

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#47 · (Edited)
The only true gains that come from an exhaust are under two possible circumstances.

If the oem system is very restrictive due to emissions or sound dampening, even with the oem tune if you open it up you will acheive gains, albeit very modest. Maybe 15-20 whp.

If on the other hand you make the engine flow better, larger volume of uptake (fuel/air/meth) and combustion (major tuning changes) with an equilibrium increase in exhaust flow, then the sky is the limit. So the actuality is its not "the exhaust", but its own link in the chain of the overall equation.

The exhaust flow is so great/efficient on my TGEN now that it wants to bypass my external wastegate even with a boost T.
 
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