Quote Originally Posted by 10KRPM View Post
Id be very surprised if you gained all throughout the rev range with a 3 inch system from the header back. Even though the 2.4 k series is a biggish 4 cylinder engine i dont think it would generate enough back pressure that a 3 inch system would then alliviate.

Back before i had the dc2r, i was getting around in an S15. 200kw at the wheels and the system was just 3 inch. The k24 is lucky to push 110 at the wheels....so 3inch is overkill.
I don't Disagree with that at all if you were to just get an exhaust there would be no need for a 3" however if you were to do more with the engine. I am planning to be pulling 160 or so kw atw soon and will be also putting cams and could look at a supercharger. My point is that if you are looking to upgrade the engine alot I would go with the 3" but if not it doesnt make much difference or any difference if you get a 2.5" or a 3" exhaust.