Intercooler piping diameter - volume vs. boost??

[King Salami]

I'd like a bit of practical advice from the resident gurus on this one...

I picked up a Supra SMIC with most of the piping included, and I'm trying to decide if I want to try to use the big, honkin' stock Supra piping & tubing (3" I think), or go with smaller diameter piping (flow vs pressure).
I'm assuming the bigger piping will give better flow at the top end, but slower spool (all other things being equal). The smaller diameter should give a faster-hitting spool, but less top end, correct?
I'm on the stock 14b (which I plan to keep). I'm shooting for 300 - 320 HP once I get a fuel pump and an RNR 2.5" turbo back this summer.
I'm also planning on a Brode 2.25" UICP since I've got ABS on my 92 TSI AWD.
I'm assuming that, since I have to neck down to 2.25" going out of the intercooler, anything over 2.5" into it would be a waste.
Any suggestions?

 

[KRAZYKOREAN]

I wouldn't go bigger then 2.5..thats all thats needed IMO...

 

[Defiant]

Originally posted by King Salami
I picked up a Supra SMIC with most of the piping included, and I'm trying to decide if I want to try to use the big, honkin' stock Supra piping & tubing (3" I think), or go with smaller diameter piping (flow vs pressure).

This is one of the things I wonder about. When an FMIC is put on, a nice big blingity-blinger one with pipes running around the front of it and up over the back and through the hatch and.... what effect does that have on pressurizing the intakes? Back in the Stone Age, we thought what mattered was having a short intake run- take a look at the Revell model of the turbo Pinto engine, it runs the exhaust all the way under the motor to get the blower next to the carburetor.
I like this setup with the liquid intercooler, but apparently it doesn't solve much because of having to cool the liquid. Sure is a nice, short intake run, though.

 

[pneumo]

Low volume piping is better for throttle response. Low volume can be acheived through short routed pipes, smaller diameter, or both. Basically there is some delay between when the throttle is opened and when the MAF starts flowing more air. That's one reason the ECU has an "Accel Enrich" function (a.k.a. accelerator pump in carburetor speak). It gives an extra squirt of fuel during rapid throttle opening. Changing the volume of the intake tract too much will mess up the throttle response.

I'm not sure how much is too much, but I wouldn't want to have 3" pipes routed to a FMIC going through the stock location first.