FMIC piping size?
 

Quick question. I have a stock 13bt s5 turbo and have a front mount intercooler with a 2 1/4" inlet/outlet. I was wondering if 3 inch intercooler piping would be too much for my setup. The intercooler core dimensions are 18"x6 1/4" x 3.5". What would the recommended piping be so as to no produce too much boost lag? thanks for the input guys!!

This is a misunderstood area of a setup. It's also difficult to know the correct answer. There have been some tests that showed an increase in power with smaller piping, due to either a larger pressure drop or the reduced peak flow allowed better heat dissipation through the intercooler. These were a couple of the theories anyways. Since you're not running a large turbo and you're boost levels will probably be on the lower side, I think 2.5" tubing would be just fine, and give you the best performance for your setup. Try to keep the bends as few and as smooth as possible. If you were running higher boost levels or have a lot of turns in your setup then running 2.75" or 3" might be beneficial due to turbulence in the piping effecting good flow. But in this case your intercooler and turbo outlet will still be the choke points of the system so it's hard to say if larger piping would be of any benefit.

Hmm ill think about these points that you brought up. Thanks for your input! if anyone else would like to give any input I would really appreciate it. Thanks guys!

I concur. 3inch is pointless at this point. if you go bigger than your intercooler inlet/outlet it is pointless. Your intercooler inlet will become the orifice(restriction) think of a garden hose with a nozzle on it. your pressure will increase and your flow decrease.

I have dynoed several cars at over 600rwhp with 2.5 inch intercooler piping.

Going big intercooler piping is just going to make your setup less responsive.

Here are some good facts regarding piping size, and remember

http://www.honda-tech.com/showthread.php?t=1202591

Don't judge just because it's a honda forum. 2.5" piping is enough to support around 930 CFM, (nearly 600whp) before the air charge starts to run into resistance. This is according to Corky Bell, so take it FWIW.

I remember seeing that thread before i just couldn't remember where. It has good information. Just keep in mind that that the measurements before the air becomes turbulent is with straight piping, so the more turns the air has to make in the system the sooner in cfm the air will become turbulent. Same thing for lots of coupler connections that create lips for the air to pass over, its also best to keep bovs on either straight sections or on the inside of a corner because as the air comes around a turn its going to be forced toward that outside edge and if there is a bov flange it's going to be forced right into that area and create a lot of turbulence.

some good info here thanks a lot guys!