[sperry]

How does pipe diameter effect this sound wave assitance?

I'm specifically interested in the exhaust side of things, because I'd like to replace my exhaust from the headers back with 2.25" pipes, two high-flow cats, a 2 into 1 resinator, split back out to two mufflers, and out through the stock tips. If I change my exhaust diameter, and/or the location/flow of the cats, how do I need to move the resinator to keep the flow assistance designed into the stock exhaust?

And back to the intake side of things, how does forced induction change the IRIS's effectiveness? I'm assuming that the change in the length of the intake pipe resulting from tossing a turbo in there will effect at least the resonance side of the IRIS.

'Course, with forced induction, you would think that the IRIS system becomes useless, and that intake manifold is less important, but I read a quote from the guy that designed the intake manifold on the WRX/STI and he said that's what he assumed when he started working on the manifold, but it turned out the opposite was true, and that it was very important to design the mainifold to match the turbo application.

I wonder if going to forced induction and short ram intakes, etc, is really just hobbling the motor and undoing a lot of creative engineering on Subaru's part.