i know most people here run 2 inch hot side and 2.5 cold side. same as me right now, and i have just shy of 2inch inlets on my endtanks (starion intercooler).

but the real question is when do you need to run bigger pipeing and why?

i just did a t3/t4 and plan on running upwards of 15psi (its on 7psi right now) is there really a point were any of us need to be running a full 2.5 inch charge setup from the turbo all the way to the mani? does the extra 1/2inch make any difference at all?

 

no. not that much at the psi you are going to be running.
my friend with a VW GTI is running about 2 inch hot side and 2.5 cold side with 23psi and no flow problem. if you want to invest extra money go ahead but i don't see a need.

 

There was a thread about this not long ago and Braineack posted up something showing an equation that 2" pipe can hold like 350hp IIRC.

 

FLOW - cubic foot per minute and balancing pressures - turbo output, intercooler inlet capabilities, intercooler flow volume, intercooler outlet, etc - seems the better balanced the total flow, the better the performance. Pipes too small, intercooler too big, yadda-yadda makes for poorer performance than having a balance across all of your stuff. A long time ago someone figured out the Starion IC's with 2" in/out and made a statement about them being more balanced against the turbo capabilities, that had to do with why they were more popular at the time. I ran the Starion setup that way and was just fine with the total performance of the system. I did a dyno years ago, can't remember what my RWHP was exactally but it was right at 200-something with my setup. I guess I'll have to find the paperwork.

Recently I decided that my pipes (mild steel) were looking a little shotty, so I am now re-doing my system with 2" out to IC, new IC that will handle about 600 cfm instead of the Starion's flow at somewhere around 525 cfm (which is perfectly good up to 5/6 lbs of boost with the stock Greddy) and 2-1/2" out the IC to the TB. Good, bad or indifferent, who knows, but I thought as long as I was re-doing things I'd make those changes.

I could have easily kept the Starion but I figured since new pipes I'd go to new intercooler as well.

 

some good info so far. but its nice that 2inch pipe will support 350hp, but with the rest of the system taying the same, will upgrading to 2.5inch yeild a gain?