I just have a quick question, how big is too big for a cat back? I will be running 5 PSI, and my friends say that a 3" cat is too big. Is this true? And if so, when I run 12 PSI, sould I upgrade to a 3"? Thanks.

 

depends on what route you go.... to be honest if you go turbo, there is the possibility of needing a bigger exhast but not till after like 15-20 psi, if you go supercharger, it's a differen t setup and won't need as much backpressure

 

rrm says 2.5 is the perfect size. don't quote me on that.

 

I think 2.5" should do fine under any daily driven situation. Last I checked, TTPR was still using 2.5" exhaust and putting out about 600hp.

 

my buddy with his old 240 had a 3 inch straight pipe. it's not too big...in japan the sylvia's came stock with a 3 inch straight pipe

 

turbo = bigger the better the turbo itsself creates the nessary back pressure to not pull fuel out on exhaust - intake stroke

 

ask turbotech_P.R. ^_^

 

Thanks for the input. I think I have decided to go with the 3" catback so that when I go higher HP, the flow will be better for my turbo.