I'm going to get a 3" Downpipe for a Turbo I am putting together. I asume it won't just bolt on to my 2.5" Cat, so where do you find a good 3" Cat, or will the 3" Down Pipe plug into the 2.5" Cat?

 

it will be able to bolt on if you get the right collectors or whatever their called. but just get a 3" cat by kamikaze or skunk2 theres a lot

 

dont cat a turbo motor.... there goes all your power. If you absolutely have to then yes get a 3". Best thing to do it find a test pipe.

 

hasnt there been studies out saying that there is not difference really between a high flow cat and a test pipe? im not sure tho

 

on stock motors it's very minimal i think less than 3hp if that. But on boosted cars it is pretty significant. Just google it and look for dyno charts you'll find plenty.

 

oh okay thanks

 

good luck.

 

I havedone a personal study, had a cat and dyno'd at 298whp on 10psi. got my testpipe put on and re-dyno'd at 308whp same 10psi.

 

you are right. The difference between a high flow catalytic converter and an open pipe is insanely less then comparing a straight pip to a stock catalytic converter.

I have a high flow catalytic converter, and it runs just as good as my friends car (same motor and upgrade parts) except he has a open test pipe.

Also, 3" isn't as cracked up as everyone thinks. Sure, it will help the turbo spool faster, but then ask yourself, why are you buying such a big turbo in the first place? You can get a tiny evo turbo and have it produce just as much power as a bigger turbo. I would go for a small turbo, which will already without a 3" exhaust, spool around 1500-2500rpm and you can keep a smaller exhaust.

When you do things right without cutting corners or buying things that are ridiculous, you can get a nice car going. For example, same motor, 2 different turbo's. Guy bought a GT60 garret turbo, other guy got a garret GT35 and was able to get exactly the same hp turnout as the other guy. Its pointless to go crazy with parts just to "look cool".

Get a little evo turbo or a t3/t4 hybrid with a 2.5 exhuast. You will make as much power as anyone else as long as you have the same upgrades (internals, build, port and polish, or other such parts)

Good luck with your car.