hey, im doing a im putting a turbo in my gslse and i dont know for sure how big of intercooling pipe ill will go. im using a stock S4 turbo, S4 tII manifold, and a NPR intercooler. the turbo and the TB plate is 2" but the NPR intercooler is 2.5".what to have boost drop either. what should i use 2", 2.25" or 2.5"? thanks

 

Are you sure your NPR is 2.5? I could have sworn mine is 2.75.

Anyway, try to run as much as possible using the same size as the intercooler outlet. You're going to need a reducer anyway, place it on the elbow before the Throttlebody.

 

mine is a small NPR one and i check it now and is 2.5". probably youre are using the big one.

 

yeah im using the smaller NPR IC and the inlet\outlet are 2.5 I used 2.5 IC piping on mine. I just finished the install using the NA elbow.

 

use all 2.5" i/c piping

 

On my single I use 2.5" to the IC & 3" from the IC to the TB inlet as this was the way I designed the IC inlet & outlet.

 

You may find as I did/do when playing with the std or hybrid turbos that use the stg WG that as you go up in IC piping size or as you make the IC more efficient that you will have masive mid range boost, that will taper off alot as you go higher up in the rev range near 7k.

See how you go.