nzae86's TRD ae86 N2 Race Car Project 2,

[4000GT]

Jimmi The Kid Wrote:I have good results with 2½ inch to the middel of the car and then step down too 2inch the rest of the way. I gain 8-10hp on my 174hp 20v with that solution, insted of 2½inch all the way. Its an old rallytrick.
Actually its because the gas gets colder at the end of the exhaust and then a smaler pipe will give a better flow.

But since you have such a short exhaust, I don't think it matters. I belive this engine will pull out 215hp+ even with a banana in the exhaust :wink:

Cant wait to see some videos

A smaller pipe does not get better flow, it increases the velocity of the gas because the pipe is smaller, following that logic you would use the smallest pipe possible. The issue is that the gasses cool, and get more dense, and slow down, and you want zero backpressure (while allowing scavenging). Because the gas is more dense and slower, you need a bigger pipe to account for the reduced capacity, the boundary layer thickness in a small pipe again reduces flow. You want a megaphone type approach, increasing in size...