Im posting this for a friend. He has a 99 LS with a vortech supercharger kit. Jun lightened flywheel, exedy clutch, DC ceramic 4-1 headers. He was running stock exhaust. He went and got 2.5 in piping 2 days ago and he swears he lost a ton of power. He wants to know what would be the best size piping to run with his setup. Im not sure How much boost hes running i think it may be 7psi.

 

wouldnt bigger only help more? The vortec kit is almost like a turbo. WOuldnt bigger be better?

 

well thats kinda what i was thinkin to. Its just a shaft driven turbo pretty much so i didnt think exhaust diameter would help it spool

 

It doesn't have the turbo in the exhaust path so it doesn't follow the same rules. It would be like NA, if you throw a 3" exhaust on then you will lose low end and gain high end... Depends on how he wants to modify the powerband. Higher exhaust velocity = more torque

 

he said he noticed some more high end but lost ALOT of low end. I dunno if hes just exaggerating about it. I was thinkin 2.25 in would be about right.