A couple of months ago everyone wanted 3" exhaust systems. Pretty much all the turbo mags say that 3" is a good size for a turbo car and then Greg Dupree says that 2.5" downpipes are better for flow than 3" and everyone has run with it. Now every joe blow on the forum is saying that 3" is overkill. Maybe 2.5" downpipes are "marginally" better than 3" downpipes, but does this now apply to the entire exhaust system? I've heard that the 3' downpipes create more turbulence at the turbo. Have you seen the turbine wheel that all the exhaust has to flow through for an entire side of the engine? Tell me that this doesn't cause some turbulence of its own. At the turbo the 3" dp's are not that much larger than the 2.5" and then they expand out alot more. I said all that to say this. Until someone hops on a dyno and proves that you lose power with a 3" system then I think everyone needs to quit saying it's overkill just because it is their opinion.
