H pipe vs. X pipe exhaust
Thread Starter
Instructor
Joined: Oct 2006
Posts: 241
Likes: 8
From: COLUMBIA STATION OHIO
H pipe vs. X pipe exhaust
I recently bought a '01 Z06 that has long tube headers, but for some reason, the H pipe was kept, rather than going to an X pipe system. The car is fairly stock except for the headers, a cam upgrade to the "02 LS6, and modifications to the 243 heads. Does anyone know how significant the switch to an X pipe would make in rwhp? I am planning on modding to approx. 550 rwhp, probably a nice cam, possibly a supercharger. I would just switch to an X pipe, but the shop that did the work on this car, a very well known Corvette shop, welded everything. I mean, everything.....no bolt up to the H pipe at the header junction. While I always do my own modifications, welding exhaust systems is not one of my strengths. I really hate to rely on other people to work on my car, so my inclination is to keep the exhaust as is. Any input on this will be apprectiated. By the way, the car dyno'd as is at 382 rwhp. I felt that it should have been around 400 - 410. Could the H pipe be restricing it to that extent?
Pro
Joined: Aug 2007
Posts: 619
Likes: 1
From: ATLANTA GA
Im gonna wait for others to chime in about the X pipe.. Im not sure Im wondering my self..
I got a friends 01 z06 with the LG headers and x pipe, My only complaint is is sounds kinda raspy at low- mid rpm..
I know in my mustang days there wansnt really any reall gain to X or H they made about the same.. But they had different sounds, Im more fond of the H sound.
385 HP to the wheels is very good. you wont get 400-410 hp never on just a header swap. Since u upgraded the "02"ls6 only made 405 at the flywheel, The 01 made 385.
if i remember right most of them are dynoing in at arround 340-350HP. So if thats correct you gained about 30-35 HP which is not shabby.
I got a friends 01 z06 with the LG headers and x pipe, My only complaint is is sounds kinda raspy at low- mid rpm..
I know in my mustang days there wansnt really any reall gain to X or H they made about the same.. But they had different sounds, Im more fond of the H sound.
385 HP to the wheels is very good. you wont get 400-410 hp never on just a header swap. Since u upgraded the "02"ls6 only made 405 at the flywheel, The 01 made 385.
if i remember right most of them are dynoing in at arround 340-350HP. So if thats correct you gained about 30-35 HP which is not shabby.
Melting Slicks
Joined: Feb 2001
Posts: 2,804
Likes: 358
From: Northville, MI
The X pipe will add more HP with a proper tune, however where you place the X pipe determines how much it will help. Extensive testing has shown the best results are right after the collector. The further down stream the less the results. If you are running cats, place it before the cats. On a head and cam car it should be worth 25-30 flywheel hp.
Thread Starter
Instructor
Joined: Oct 2006
Posts: 241
Likes: 8
From: COLUMBIA STATION OHIO
Well...I guess this is the reason I asked. There are a few different opinions on this. On my '99 Corvette, I installed an X pipe along with catbacks, when I installed the lg headers. I stopped at the Corsa plant here in Ohio...it's 5 min. from my shop. When I asked the question "why should I go to an X pipe?" the guy brought out a cut off section from a stock Z06. I was amazed that when the exhaust gets to that H area, the size of the hole shrinks down to maybe about the size of a nickel...maybe slightly larger. Being that far down the line, I am not sure if it really is that big of a factor, though.
Melting Slicks
Joined: Feb 2001
Posts: 2,804
Likes: 358
From: Northville, MI
The H pipe is a 5/8" hole located past the cats and is used for sound purposes to balance exhaust pressures. An X-Pipe is a 2.5 or 3" crossover allowing the exhaust to flow faster. The closer the X is to the heads the easier it is for it to draw the exhaust out of the heads leaving better makeup of air/fuel burn.
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Melting Slicks
Joined: Nov 2005
Posts: 2,297
Likes: 156
From: Clayton New Jersey
I had the X Pipe and Z06 cat back. I went to the full Z06 exhaust including H-pipe. Seat of the pants, I would say the H Pipe feels better. I do get some popping on decel but I think it feels and sounds great. 
Good Luck
Good Luck
Le Mans Master
Joined: Mar 2002
Posts: 8,466
Likes: 51
St. Jude Donor '17
The H pipe is a 5/8" hole located past the cats and is used for sound purposes to balance exhaust pressures. An X-Pipe is a 2.5 or 3" crossover allowing the exhaust to flow faster. The closer the X is to the heads the easier it is for it to draw the exhaust out of the heads leaving better makeup of air/fuel burn.
x-pipes that replace cats are a different breed compared to the x-pipe corsa sells to replace your h-pipe.
Last edited by Got uid0; Feb 17, 2008 at 11:36 AM.
Former Vendor
Joined: Nov 2005
Posts: 8,995
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From: Spring Texas
St. Jude Donor '08
you loose the "burble" and the popping sound with backflow. You will get a power gain, but it's minimal at best.
Original Founding Member!
Joined: Jul 1999
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From: Granby, MA
Cruise-In 1, 3, 9. 10 & 11 Veteran
more hp......I dont' believe it.....
I would love to just see a dyno graph on this, cause for the 3-5 hp that some people are saying you gain....I think its all smoke and mirrors.....sorry guys....gotta call 
Lets see a dyno graph of 2 identical systems with the only difference being X or H pipe.
Only thing I have seen proven is you get a different sound from the x pipe.
Lets see a dyno graph of 2 identical systems with the only difference being X or H pipe.
Only thing I have seen proven is you get a different sound from the x pipe.
Le Mans Master
Joined: Mar 2002
Posts: 8,466
Likes: 51
St. Jude Donor '17
I would love to just see a dyno graph on this, cause for the 3-5 hp that some people are saying you gain....I think its all smoke and mirrors.....sorry guys....gotta call
Lets see a dyno graph of 2 identical systems with the only difference being X or H pipe.
Only thing I have seen proven is you get a different sound from the x pipe.
Lets see a dyno graph of 2 identical systems with the only difference being X or H pipe.
Only thing I have seen proven is you get a different sound from the x pipe.
Otherwise stock a4 fresh f1 super car 295 tires, cold air, and x pipe and corsa indy
12.9
Dropped 3-4 tenths off my average run. Not sure if it was purely the tires alone or the combination.
Le Mans Master
Joined: Sep 2004
Posts: 5,707
Likes: 4
From: Los Angeles
I would love to just see a dyno graph on this, cause for the 3-5 hp that some people are saying you gain....I think its all smoke and mirrors.....sorry guys....gotta call
Lets see a dyno graph of 2 identical systems with the only difference being X or H pipe.
Only thing I have seen proven is you get a different sound from the x pipe.
Lets see a dyno graph of 2 identical systems with the only difference being X or H pipe.
Only thing I have seen proven is you get a different sound from the x pipe.
If it was that easy to gain 5 hp, GM would be all over it. It costs nothing for the factory to install an X pipe instead of an H. It is for the sound only as equipped from the factory. The X pipe MAY add 1hp if you are using equal length headers and a tune.
Melting Slicks
Joined: Oct 2007
Posts: 2,724
Likes: 2
From: Holland Landing Ontario
Here's a web site that shows some real #'s.
http://www.vetteweb.com/tech/0307vet...nfo/index.html
Dave
http://www.vetteweb.com/tech/0307vet...nfo/index.html
Dave
Safety Car
Joined: Sep 2007
Posts: 4,011
Likes: 492
From: South Florida
I think of of the sponsoring shops should man up and dyno a setup w/an h-pipe 3-5 times to get an average baseline, and then in the same day swap the H w/an X and re-dyno 3-5 times and average 
Le Mans Master
Joined: Sep 2004
Posts: 5,707
Likes: 4
From: Los Angeles
Here's a web site that shows some real #'s.
http://www.vetteweb.com/tech/0307vet...nfo/index.html
Dave
http://www.vetteweb.com/tech/0307vet...nfo/index.html
Dave
Le Mans Master
Joined: Mar 2002
Posts: 8,466
Likes: 51
St. Jude Donor '17
The reason an X-Pipe crossover works better than an H-pipe crossover isn't more flow because of volume, but more effective use of exhaust gas velocity. Exhaust gas (or air) has surface tension, and flows much like liquid would through the same pipe system.
Last edited by Got uid0; Feb 17, 2008 at 11:01 PM.
Le Mans Master
Joined: Sep 2004
Posts: 5,707
Likes: 4
From: Los Angeles
Gee, if GM only knew that in 2001 they didn't have to change the injectors and intake manifold to bump from 345hp to 350hp! All they had to do is add an Xpipe and they could have got 354hp!
Boy are they ever a bunch of idiots there.
Last edited by robvuk; Feb 17, 2008 at 11:37 PM.