hi, i'm putting together a ls/vtec turbo for a friend, hes goal is 350-380 hp
for DD. It's capable a 2.5 downpipe with a full 3" exhaust and in fully build ls/vtec with a precision 3431E to made that power. I know 3" is the better
but the guy is short of cash and the car already have 2.5

thanks in advance

 

A 2.5" downpipe is not going to stop the setup from making that power; it'll work....Will a 3" DP work better/more efficiently...yes.

 

Autoworks thanks for the reply knowing you are a FAB Specialist. Now
i feel more secure to what tell to the guy.

thanks
carlos

 

Turbos work on a pressure differential. The lower the pressure on the exducer side of the turbo, the better. We'd all run 3 inch, 4 inch, open down pipe, heck, even blow it out the hood...
I went with 2.5" because it's quiet. It's a sacrifice for making power as easily, but the car has to stay quiet...