Hi guys,

I have long tube headers into 2.5" mandrel bent exhaust with x-pipe and flowmaster race mufflers. Header collectors are 3". Motor on the dyno made significantly more power with open headers. I have a custom exhaust setup and it is extremely tight around the rear axle and suspension. I only have room to increase to 3" pipe from the headers back about 4 feet. I want to keep my full exhaust.

I know that exhaust gases take up less volume as they cool. I also know that the exhaust cools as it travels down the pipes towards the back of the car. I was wondering about the theory that I could increase the pipe diameter from 2.5" to 3" for the first half of the exhaust and then hook up with the existing 2.5". Would this gain me anything?

thanks for your comments

 

I think it would show a benefit. As you said, the gas cools as it travels through the system and cools a great deal while it is doing this. As a gas cools, it looses volume.

 

Thanks for your comments.

Anyone actually have an exhaust setup like this?

 

I have 3" long tubes into a 3.5" single that necks down to a 3" catback. I know I'm leaving a bit on the table but I can still have a conversation comfortably.

A dual 2.5" setup isn't really too bad unless you are running big CI or boost. What was the power difference between open headers and full exhaust. If it's even remotely quiet I'd guess about 20rwhp.

 

Good guess, it was about 20rwhp

 

Have you thought about tryint to keep the heat in the pipes to keep velocity up? I have been doing something odd on my cars for years and it works well for me. On my GTO, I have 3 inch collector headers with 3inch midpipes into a 2.5inch duals. I have the headers and midpipes JetHot coated and wrapped, the exhaust is wrapped almost to the rear diff. Cuts down on the tinny sound of the headers and has always made better than average power. I haven't tried back to back tests, so it's all theory. Last 2 mid engined turbo cars I worked on, everything was wrapped from the heads all the way up to the exhaust tips. Keeps the temps down under the bonnet also. Only downside is, a lot of people hate exhaust wrap...

 

Saw this on another forum...
Where do yours fit in?
Gibson SuperFlow 788200............................................ ..311
TTS Bullet Cat Converter......................................... ........324
Flowmaster 40 series 42540..........................................352
Flowmaster 50 Series............................................ .........362
Flowmaster 40 series 43040..........................................392
Dynomax Super Turbo............................................. .......410
Flowmaster 62631............................................. .............435
Carsound Cat Converter......................................... ........436
FLP Cat Converter......................................... ..................440
Edelbrock Victor 5535.............................................. ........562
Flowmaster 40 series 435409..........................................57 6
Edelbrock RPM series 5511.............................................. 579
Flowmaster Delta Force Racing 54040-10........................634
Edelbrock 304 series 5560.............................................. .640
Edelbrock Gen App 5505.............................................. ....708
Dynomax Race Magnum Welded 17216...........................711
Borla XR-1 40600............................................. ................836
Borla XR-1 40615............................................. ................854
Dynomax UltraFlow SS 17263..........................................100 0
Dynomax Race Magnum Welded 17218...........................1000
Borla XR-1 40575............................................. ................1100
Dynomax UltraFlow......................................... .................1133
Edelbrock Victor 5537.............................................. ........1400
Borla XR-1 40450............................................. ................1400
Borla XR-1 40741............................................. ................1450
Dynomax UltraFlow SS 17296, 17268..............................2200
Dynomax Race Magnum Welded 17220, 17224...............2200
Dynomax Race Magnum Welded 17225...........................2600

Read more: http://www.corvetteforum.com/forums/...#ixzz3qztUSDzy

 

It's not unheard of to do this. Select mufflers that can flow the CFM your motor needs paired with pipe diameters that can handle that flow and place a cross over at the right location you should be good to go.