I've got the Greddy 15G turbo kit and the down-pipe is only 2" internal diameter... I am doing the rest of the exaust, including the cat, in 2.5" diameter piping. How much negative effect is the 2" down-pipe going to have? I am welding in the slash-cut tube for the crankcase ventilation today and finally had it out to measure... I had assumed it was at least 2.25" or so, but that is not the case.

As an FYI this car will be running at most 8 PSI. If I decide to go higher than that the DP will be upgraded to match the 2.5" piping behind it.

 

i had a greddy 15g kit logn time ago and was running 10psi.. i switched to a kteller 2.5" downpipe and it made a HUGE difference!

http://www.kteller.biz/prodtyp...y=cat

 

Oh, wow! I didn't notice that for sale over there Thanks alot.

 

I'll be okay as long as it bolts up to the Greddy kit. Now that I know where to get it, I'll have it first and have the rest made to fit with it all at once.

 

mine was fine..

 

Good tip on the J-Bend... I'll have to look into that