I'm sorry but it's not really a new theory its established physics...

An ideal exhaust design would have a constant mach number around .2 and the amount of air you would flow at 650 crank hp equates to almost exactly that assuming a 16ga tube with a 4" OD... what that means is anywhere you have over ~585whp you SHOULD be using a 4" exhaust. Without redoing all my calcs I would guess that anything over 425 would benefit from a 3.5" exhaust. Of course there might be something to gain from having a smaller exhaust before the turbo spools when your in the 300-350 range so maybe some spool could be gained. In the end though if your making 550+ a 4" exhaust is going to net you a better powerband.

Theory's that contradict textbooks are almost always wrong

 

well im past the 700 mark using 3 inch, i think your physics may need some adjusting

 

you can make over 1000 on 3"... doesn't mean it's ideal

That's along the lines of saying don't buy slicks I run 10's on street tires

Of course it's possible I should just throw my old textbooks away they are probably wrong, I can't believe no engineer in the past decade has noticed and corrected that problem

 

Turbulence is a better word for what your describing I do believe. 2" on a 400hp car would be better described as a back pressure scenario, your right.

The act of too big of exhaust does what your explanation in tales, but that

 

[QUOTE=s2000Junky,Sep 22 2009, 01:00 PM] Turbulence is a better word for what your describing I do believe. 2" on a 400hp car would be better described as a back pressure scenario, your right.

The act of too big of exhaust does what your explanation in tales, but that

 

[QUOTE]Someone can do the math I

 

yea no kidding, at that point is a large "mass" that wants out as fast as possible. Think water flowing out a pipe. I am almost 100% certain that a 4" would help but how much I dont know.

 

[QUOTE=btstone84,Sep 22 2009, 09:47 AM] well im past the 700 mark using 3 inch,

 

Andy, bstone is another one of those who has to argue with everyone and always thinks hes rights.

 

Oh I know, its odd that he can say something but then not back it up with any evidence. Like Momentum who we all know, knows his stuff. He says something and then Bstone says " well you better check your physics cause they wrong " or something.

Its actually funny to read his posts because like in the case of him calling out physics...thats hilarious. Physics dont lie...when making a certain amount of power which momentum stated a 4" exhaust would actually increase power. But since Bstone doesnt work on his own car and has a well known shop do it for him we know that what he has to say holds about as much water a a tin can shot with a shotgun.