Pipe diameter and max HP

[Wez]

Hey All,

Does anyone know what affect smaller pipes have on HP output.

Most single turbos have a 4"/100mm inlet, I was wondering what would be the effect of reducing this down to 3"/70mm with an inline filter fed directly from outside.

:cool:

[michel lane]

i changed down from 4 inch to 3 inch , i lost 200-300 rpm in spool and the car is not as responsive, but much quiter,i have changed back up now and put a bigger amp in the car...but saying this iam running a 74mm turbo.