Since we are all buzzing about exhausts today: X-Pipe vs H-Pipe vs Straight Pipe

[Flying Tomatoes]

Has any one done any research on this? I know there are many different systems out there running many different configurations. For example I have the MTM which uses and H-Pipe but many after market companies go with the X-Pipe. I know the sound differences are noticeable but is there any information that shows one is better then the other performance wise? Maybe its better in some situations to have one or other situations to have another?

While this vid isn't RS4 related it is an interesting study on the differences in configurations. The results were shocking to me but I'm anxious to see what you guys think.

[Jake@JHM]

The X-pipe is used more often because of the scavenging affect.

[NY07RS4]

The x pipe is advantageous to us 4.2 guys due to our cross plane v8. Like Jake said the x pipe will maximize the scavenging effect and will be the most efficient at getting the exhaust moving and keeping the pulses happy.


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[Flying Tomatoes]

While I understand that the x-pipe makes more sense in theory, I was looking to see if any one actually tested this. If you watch the video above the straight piped exhaust with no cross over yielded the largest peak gains. Our OEM system also has no cross over. I can't imagine they designed it that way because it was the least efficient option?

[NY07RS4]

I'll let another person(s) respond, there is one company that I know of that tested the different options and they chose the option that best suited our type of engine and now sell the product. There is more R&D behind the testing of this particular exhaust than most would even believe if shared here. There are also threads (that I'm admittedly too lazy to search for and link to) that went into some of the particulars of this R&D and the results. From flow testing through track testing. At a large well known respected facility (OEM) and private track rentals. I'll shut up now and let the more informed chime in.

[beemercer]

While I understand that the x-pipe makes more sense in theory, I was looking to see if any one actually tested this. If you watch the video above the straight piped exhaust with no cross over yielded the largest peak gains. Our OEM system also has no cross over. I can't imagine they designed it that way because it was the least efficient option?

if the california has a flat plane crank V8 like lots of other ferraris their results (as far as exhaust crossovers) are not applicable to the cross plane crank V8 in the RS4 and most other V8s.

flat plane V8 functions like two I4s joined at the crank vs a cross plane being more akin to two V4s joined front to back. the cross plane V8 has an uneven firing order whereas the flat plane is even. the uneven firing order causes unbalanced exhaust pressure bank to bank, and makes the crossover advantageous.

one way to make the exhaust of a cross plane V8 work like a flat plane V8 below (Bundle of Snakes). this is better than an x-pipe in the secondary of the exhaust since it will eliminate exhaust pulse crowding in the collector (collector sees an exhaust pulse every 180* of crank rotation vs 90*, 180* and 270* for a cross plane)



the X is normally preffered for performance on a cross plane V8 because it does a better job of forcing the two streams to interact. only tests I've seen involved an old pushrod V8 and 1/4 times, searching for it now.

here's one article
http://www.carcraft.com/techarticles..._installation/

and a recap from another article that I can't find the link for

[Auditude2.0T]

Someone should dyno an h-pipe v. x-pipe to see the difference.

DYNOS FTW

[wahpao]

"Why an X-pipe? Naturally Aspirated V8s always make more power with an X-pipe. The location and size of the X-Pipe in the JHM B7-RS4 Cat-Back Exhaust System has been meticulously researched and developed to produce the best scavenging of the exhaust pulses coming from either side of the motor. The location of our X-Pipe also gives the 32-valve V8 motor a cleaner, more refined tone." - JHM

Not sure if that means they did the research or a know fact in the V8 world. V8s have been around for a long time and the same theories and principles apply to all exhaust systems across the board be it mustang, corvettes or RS4s. The theory is H has more low end tq and the X has more top end hp. Somebody correct me if I am wrong.

[Mistro]

Pretty sure the california is flat-plane. (even firing between banks)

With a cross-plane you're going to get two sets of two subsequent firings on the same bank.

For example the firing order on the RS4 is 1,5,4,8,6,3,7,2. (ie: 8,6 and 1,2 are together)

edit: Doh, beaten by beemercar :)

[Flying Tomatoes]

The California is a flat plane 8 cylinder, yes.

Lots of good chatter here.

I've heard rumor that there was a study done by one of the big european exhaust manufactures on these exhausts but I can't seem to find anything. While I know the x-pipe is commonly accepted as the better option for the V8 it makes me wonder when there are still new high performances V8 cars coming out with different configurations. This to me says that its not quite so cut and dried. For example the new Z28 has an H-Pipe.



Beemercer, that chart is quite interesting. This is the sort of results I would expect to see. Some sort of trade off in down low response vs up top. Based on that chart only (didn't dig into the link yet, but I will at lunch) you could probably say that the JHM exhaust uses an X-Pipe because they favor the drag strip and down low day to day power vs a company like MTM (only using this example because they are both 2.75 and have different crossovers) which might have favored top end Autobahn like driving. Not that either is better, just different end goals.

I've also read that if you have catalytic converters of any kid that a cross over essentially becomes irrelevant as the air is already so disturbed. I will see if I can dig up that article again as it was quite interesting.

[beemercer]

Sound goals are important too. The Z28 may have an H to retain the classic american V8 burble (caused by uneven flow). Truduals will have the most burble, Ginkof had truduals on his S4 and it sounded very American/choppy/burbally.

And yes, having cats before the crossover tends to disrupt things. Ideally you have collector, secondary, cross over, then any restrictions (cats, resonators, mufflers)

[JimmyBones]

Beemercer, that chart is quite interesting. This is the sort of results I would expect to see. Some sort of trade off in down low response vs up top. Based on that chart only (didn't dig into the link yet, but I will at lunch) you could probably say that the JHM exhaust uses an H-Pipe because they favor the drag strip and down low day to day power vs a company like MTM (only using this example because they are both 2.75 and have different crossovers) which might have favored top end Autobahn like driving. Not that either is better, just different end goals.

This is how I know that you are a troll. Please put your signature from the end of February back so everyone else knows right away when you post too. If you don't remember what that was then I will remind you:

I'm just a fat nerd with a bad beard and a stancetarded RS4. I don't have any idea what I'm ever talking about. #trollmato

"Why an X-pipe? Naturally Aspirated V8s always make more power with an X-pipe. The location and size of the X-Pipe in the JHM B7-RS4 Cat-Back Exhaust System has been meticulously researched and developed to produce the best scavenging of the exhaust pulses coming from either side of the motor. The location of our X-Pipe also gives the 32-valve V8 motor a cleaner, more refined tone." - JHM

I mean how could you seriously miss this response where wahpao quoted JHM's website about the X-pipe that they use. IT WAS TWO POSTS UP!

You must have been getting your ass kicked so badly in the other exhaust thread that you had to start a new thread to intentionally post lies.

[EUROSWAGR]

#ownedbyJimmybones

/end thread

[Flying Tomatoes]

Talk about a touchy group...

I think its perfectly logical to say that one company designs their products for a different purpose then the other just as people would buy different products for different purposes? Especially when you look at some of the data that's been presented in this thread, such as this:



The point of this thread isn't to compare products, its to compare data and see what's really and truly the best option (speaking on performance only) as there seems to be many variations such as:

Straight pipe:

OEM
Eisenmann
Tubi
Capristo

X-Pipe:

AWE
EBWerks
Magnaflow
GMG
JHM
Supersprint

H-Pipe

MTM
Milltek

I-Pipe (Y-Pipe?)

Scorpion

If there was one variation that was best for all situations I don't think we would see so many different set ups? Now obviously its been proven that some of these don't create any power what so ever but its still worth exploring IMO.

To be honest, if we could prove an x-pipe was more effective I would cut my h-pipe out and replace it with an x-pipe. It would be a simple and cost effective mod if there were gains to be had.

[S4Per]

When I did my exhaust, AMD tested - via dyno - output of my 3" (front to back) system , no cats, in the following configurations to see which one was best for the car:

• H-pipe
• X-pipe
• Straight back on both sides

Verdict: sound was richest with X-pipe. Power output was highest with X-pipe (by somewhere around 9-10 whp IIRC. No I don't have dyno sheets). Straight back sounded awful apparently (I wasn't there).

Near finished system:

[beemercer]

I was like, wtf is an I-Pipe, then I saw this:



it may be better classified as a Y-pipe (from a function standpoint). Y-pipes are pretty common on GM F-Bodys if you want to reference Y-pipe vs a crossover

[Flying Tomatoes]

Per, if you had dyno graphs your post would have been perfect, haha. I wonder if it affected the midrange curve at all or just a flat improvement all through the rev range? Do you recall?

I was like, wtf is an I-Pipe, then I saw this:



it may be better classified as a Y-pipe (from a function standpoint). Y-pipes are pretty common on GM F-Bodys if you want to reference Y-pipe vs a crossover

I have a 4th Gen f-body and it does run into a y-pipe but then straight into the muffler, then splits from the muffler. I guess its a similar idea but I have never seen an exhaust y in and then y out again like this, haha.

[zmon]

Someone should dyno an h-pipe v. x-pipe to see the difference.

DYNOS FTW

HAHAHAHA

[jdmnomore]

Seriously JHM posts and this guys response is yea but.. lets find out from people who have researched this subject smfh. Who do you think has the most cumulative research and info on this subject? Way to try to take away from the fact that clearly JHMs X-PIPE design is the most effective currently on the market.

[meistah]

There is so much research and info already posted and discussed for the 4.2 in the past. Along with a number of people who switched from H pipe to X.

[Jake@JHM]

The X-pipe costs more, which is probably why some companies don't use it. Some companies also don't design their exhaust for optimal performance, as they are going for a specific sound.

[meistah]

#capristo

[Flying Tomatoes]

There is so much research and info already posted and discussed for the 4.2 in the past. Along with a number of people who switched from H pipe to X.

Could you please post it? I've been around here for 3 years or so and have never seen any research like that.

Some companies also don't design their exhaust for optimal performance, as they are going for a specific sound.

Absolutely, and to some people that's more important!

[meistah]

Could you please post it? I've been around here for 3 years or so and have never seen any research like that.

Makes sense, they must not have had the search button for the last 3 years. I found so many links it's not worth posting all of them since you clearly didn't look.

I even tried searching by misspelling the word exhaust, and was able to find information on the x-pipe.




For information sake here is a good read. This came up on the first page of results when I searched, I didn't even have to scroll down to find it.

http://www.audizine.com/forum/showth...ing-RS4-H-Pipe

[washyourrhands]

Makes sense, they must not have had the search button for the last 3 years. I found so many links it's not worth posting all of them since you clearly didn't look.

I even tried searching by misspelling the word exhaust, and was able to find information on the x-pipe.




For information sake here is a good read. This came up on the first page of results when I searched, I didn't even have to scroll down to find it.

http://www.audizine.com/forum/showth...ing-RS4-H-Pipe

maybe you should scroll up and read the thread more carefully. This is not about the difference between the ECS H Pipe and an X pipe. It is about testing between these 3 types of "Crossovers" for the lack of a better word. Yes there is a ton of info on the ECS H-pipe. He wants to know if there is testing for why a company chose a X pipe over an H pipe or straight pipes on their exhaust. His MTM has a H pipe.

this is appropriate... lol

[meistah]

Did you read the thread or the title lol. Lots of info about x pipe testing in general.

[Mistro]

maybe you should scroll up and read the thread more carefully. This is not about the difference between the ECS H Pipe and an X pipe. It is about testing between these 3 types of "Crossovers" for the lack of a better word. Yes there is a ton of info on the ECS H-pipe. He wants to know if there is testing for why a company chose a X pipe over an H pipe or straight pipes on their exhaust. His MTM has a H pipe.

read the thread

[washyourrhands]

read the thread

people saying X pipe is the way to go is not testing

[Flying Tomatoes]

Did you read the thread or the title lol. Lots of info about x pipe testing in general.

read the thread

This is the only real data provided in the thread.

All V8 engines, with 9O degree cranks, have an out of sync imbalance in their firing order between the right
and left cylinder banks. Yes, they do go "tsoing-Boing", The firing order imbalance is a necessary sacrifice for
dynamic balance of the rotating and reciprocating crank, rods and pistons. Each time the firing order is completed
(two full revolutions), two cylinders within each bank will fire and exhaust within 9O degrees of each other. These
two cylinders will be exhausting into the header collector or exhaust manifold almost simultaneously. This
overlapping condition creates a lot of back pressure and a pop sound. Meanwhile the opposite exhaust manifold
has no activity (or pressure in it at all, This is where the characteristic, low harsh popping V8 sound comes from,
The most common way of reducing this out-of-sync imbalance is with rebalancing crossovers such as H pipes and
over-and-under X style crossovers. These provide both noise reductions and efficiency (power) improvements. H
pipes are effective only at low and mid range. The over-and-under X crossover works a little better but still does
not completely rebalance the exhaust at high RPM.

This just goes over what we have already talked about and it doesn't explain which is truly a better option. It says X-pipes are "a little better" but its really not quantified.

Am I missing something?

[jfunkey]

Yes you are missing the last 15 years of proven x pipe designs and testing in every other platform and market both domestic and import...the x design has been tested so many times I'm not surprised with how little you research anything you didn't know that.


Here are some real world results. The guy just chenged his cat back and got great performance improvements

http://audirevolution.net/forum/index.php?topic=2456.0

[Flying Tomatoes]

Here are some real world results. The guy just chenged his cat back and got great performance improvements

http://audirevolution.net/forum/index.php?topic=2456.0

This is exactly what I was looking for in this thread. Great point of reference and good data gathering! Now hopefully we can see similar data from other set ups

[ShockwaveVT]

This is how I know that you are a troll. Please put your signature from the end of February back so everyone else knows right away when you post too. If you don't remember what that was then I will remind you:

I mean how could you seriously miss this response where wahpao quoted JHM's website about the X-pipe that they use. IT WAS TWO POSTS UP!

You must have been getting your ass kicked so badly in the other exhaust thread that you had to start a new thread to intentionally post lies.

All this over a whats obviously a typo or mixup? You can correct his error in a polite manner and avoid having that Joker meme seem so appropriate.



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[jfunkey]

This is exactly what I was looking for in this thread. Great point of reference and good data gathering! Now hopefully we can see similar data from other set ups

You can so far the smart people and a few even tested and shared that x was better.

The rest of us will be in 2014 where we have alread researched data and read first hand results from rs4 owners acknowledgeing the x pipe is better results and you can keep on with this thread...

[Flying Tomatoes]

You can so far the smart people and...

Try again...

acknowledgeing the x pipe is better results

one more time...

And for the record, you are again saying there is data out there some where (at least I think that's what this broken English is implying) and you are not presenting it. Thanks for the contribution.

[beemercer]

finally found the writeup I mentioned
http://www.pontiacstreetperformance....p/exhaust.html
page 2 & 3 have info on crossovers


http://books.google.com/books?id=O--...0level&f=false
more info, X pipe has less backpressure at all engine speeds but especially higher engine speeds
they also measured the sound intensity level to be substantially lower with an X pipe at medium RPM with most varieties of mufflers


http://www.superchevy.com/technical/...t/0505phr_exh/
moar, article had input from someone close to the 4.2 world




videos explaining some differences

[ShockwaveVT]

finally found the writeup I mentioned

http://www.pontiacstreetperformance....p/exhaust.html

page 2 & 3 have info on crossovers

Wagon content: found. :D
Thanks for the link.

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[Flying Tomatoes]

finally found the writeup I mentioned

http://www.pontiacstreetperformance....p/exhaust.html

page 2 & 3 have info on crossovers



http://books.google.com/books?id=O--...0level&f=false

more info, X pipe has less backpressure at all engine speeds but especially higher engine speeds
they also measured the sound intensity level to be substantially lower with an X pipe at medium RPM with most varieties of mufflers

great read! my faith in this website is restored

[Flying Tomatoes]

http://www.superchevy.com/technical/...t/0505phr_exh/
moar, article had input from someone close to the 4.2 world

I'm going to copy paste one portion of this article here just because I feel its extra relevant and something a bit different from some of these other articles.

Virtually all V-8 exhaust systems can be refined by the addition of a balance or X-pipe. These have two potential attributes: increased power and reduced noise. Extensive dyno testing on both of these factors has indicated balance and X-pipes are 100 percent successful at reducing noise. The reductions amount to a minimum of 1 dB to a maximum of 3 dB with 2 dB being common. As far as power is concerned, things are a little less certain. With engines between about 325 to 550 hp, experience indicates that in about 60 percent of the cases (mostly with balance pipes), the engine can deliver as much as 12 additional hp, with 5-8 being the most common. The other remaining 40 percent tested showed virtually no change in output either up or down. Based on such results, we can conclude that a balance or X-pipe is always a positive asset and never a negative.

Fascinating

[NY07RS4]

If you realized who/what was involved with what you stated as fascinating, in all seriousness you would probably apologize to the "other team" for a lot of stuff that has been said since you joined the B7 RS4 forum.

[NY07RS4]

Great info as usual Beem.