General exhaust tuning guidelines/tips

drewski86 · 12-11-2008, 10:14 AM

With a turbo you really just want to get the exhaust out as efficiently as possible. You don't want to go any smaller than the turbo exit diameter. Pre-turbo most use 2" OD pipes and keep runners equal length. The thing with turbos are you can always raise boost to overcome poor exhaust.

It is also optimal to have the header run out a few inches from the motor before the first bends and to keep the bends smooth. There is a lot of theory that floats around about exhaust design. Some speak highly of expansion chambers while others say it won't work since it is a 2-stroke design. Some say run the primarys back to the rear diff. (>90") before merging for a road race setup, while all of the ITS (stockport) and EP (streetport) cars I've seen run ~24" primarys.

Ender · 02-25-2009, 09:40 AM

Quote:

Originally Posted by drewski86

The thing with turbos are you can always raise boost to overcome poor exhaust.

You can try. When I had a bad exhaust set up on my TII I could crank it up to 12psi, but it would fall to 6psi within 2 seconds of reaching peak boost, so the extra boost was essentially rendered useless just because of restrictive exhaust.

drewski86 · 02-25-2009, 10:05 AM

Quote:

Originally Posted by Ender

You can try. When I had a bad exhaust set up on my TII I could crank it up to 12psi, but it would fall to 6psi within 2 seconds of reaching peak boost, so the extra boost was essentially rendered useless just because of restrictive exhaust.

What do you mean by "bad exhaust"? I would say you had other issues than just bad exhaust.

Ender · 02-25-2009, 08:51 PM

Quote:

Originally Posted by drewski86

What do you mean by "bad exhaust"? I would say you had other issues than just bad exhaust.

It was restrictive. As soon as I replaced the muffler that was in the middle of the system with a piece of flex pipe it boosted fine.

drewski86 · 02-27-2009, 10:35 AM

Quote:

Originally Posted by Ender

It was restrictive. As soon as I replaced the muffler that was in the middle of the system with a piece of flex pipe it boosted fine.

I guess everything has limits.

12-11-2008, 10:14 AM	#1
drewski86 Slow Join Date: Jun 2008 Posts: 38 Rep Power: 0	With a turbo you really just want to get the exhaust out as efficiently as possible. You don't want to go any smaller than the turbo exit diameter. Pre-turbo most use 2" OD pipes and keep runners equal length. The thing with turbos are you can always raise boost to overcome poor exhaust. It is also optimal to have the header run out a few inches from the motor before the first bends and to keep the bends smooth. There is a lot of theory that floats around about exhaust design. Some speak highly of expansion chambers while others say it won't work since it is a 2-stroke design. Some say run the primarys back to the rear diff. (>90") before merging for a road race setup, while all of the ITS (stockport) and EP (streetport) cars I've seen run ~24" primarys. Last edited by drewski86; 12-11-2008 at 10:17 AM.