KATYB wrote: In reply to mblommel: what im saying it is is less than 1 percent. on the intake side of things and headers yes it makes a difference but on the overall exhaust system not so much. reason being, exhaust is not a constant flow its pulsed thus doesnt make that much of a difference if any.
I have to completely disagree on the point of exhaust flow not being pulsed. It is in fact a series of standing waves that can absolutely be tuned to produce a scavenging effect and a therefore a power increase. Half of my senior design project for my BSME was based on this fact. I suggest you pick up a copy of "scientific design of exhaust and intake systems" by Smith and Morrison if you want a basic understanding of the concepts.
EDIT- I misread your post, you were in fact saying it's pulsed not the other way around. Sorry I'm a douche. Either way Smith Morrison is a great read for exhaust system design and on smaller engines every little bit helps. Heck, even on big engines every little bit helps. I'm sure there are NASCAR teams out there who would kill for 10HP just by changing their exhaust system bends.
