Intercooler Piping Diameter

[GTS25-t]

Hey guys, Ive been looking at several intercooler kits for my gtst. The cheaper ones come with 2.5 inch piping but the more expensive ones come with 3. Is it really worth spending the extra few hundred and get the 3" piping? I mean i know that the larger diameter will flow better, but is it going to make a difference that will justify spending more money?

Come to think about it, anyone know the throttle body diameter for an RB25det off the top of their heads?

[lebostyles]

from what i have heard, the 3 inch piping will be very laggy, but depends on your modifications

[QRI05E]

2.5" piping is more then enough... it will keep turbo lag to a minimum as well as give you an even flow with your stock intake pipe...

The FMIC core flow is what will cool the air and give you best perfoemance... Have a look at the Gktech FMIC kit in the group buy section...

http://www.skylinesaustralia.com/forums/in...howtopic=120149

Best value for money!

Cheers

[Sydneykid]

Come to think about it, anyone know the throttle body diameter for an RB25det off the top of their heads?

70 mm

cheers

[justin911]

while were on the subject of throttle bodies...

would going slightly larger be an advantage for rb25det ??? and wat size would u recommend ?

[Sydneykid]

while were on the subject of throttle bodies...

1. would going slightly larger be an advantage for rb25det ???

2. and wat size would u recommend ?

1. No, not until you are well and truly past the limit of the standard internals

2. See #1

cheers

[mad082]

the standard piping is only about 2.5" so there is no point going bigger unless you are changing the whole piping. also 3" means a bit more lag.

[WazR32GTSt]

hte entire intake piping is only as big as its smallest component

thus, if the standard throttle body is 70mm then that is the max you should bother going.

Waz

[rice_me_up]

that is interesting..... does any one (more like Sydney kid= any one) know what the throttle bodie diameter for the RB20 is??

cheers.

[HRthirtyone]

i got 3inch piping on my rb20, and will gladly swap with anyone back to 2.5inch.

[The Dan]

T/body diameter should be the same for both.

There is no point going to 3 inch pipe work unless you are doing a major upgrade and seeking more than 400hp at the wheels. There is also no point upgrading the pipework if you are running standard cams as your hp limit will be around 230-240rwkw anyway and the 2 1/2 inch piping is more than capable of handling up to 300rwkw and over. The outlet on the turbo should only be around 2 - 2 1/4 inch as well so adjusting for some expansion would take you to the optimum diameter of 2.5

[GTS25-t]

Ok thanks guys, 2.5 inch it is. My exhaust is getting made up tomorrow so the intercooler is next on my list.

[LiQuid IcE]

Similar type questions...

1. Does the 'fatness' of the cooler make a lot of difference...?? Ive seen them from say 65mm thick to 100mm?

2. Is the cooler only as effective as the the surface area exposed to the rush of air... (ie is the area of intercooler blocked by the front bar useless?)

Because I was thinking of just getting a cooler that wasn't as 'tall' as the usual 300mm and going for something half as tall.

[BiRDY]

the thickness of the cooler only really adds to lag unless u got mega horsepower, id say nething more than 75mm thickness is a waste for up to 20psi..

and yes a coola behind a bumper will not be as affective as a cooler with direct air flow... ie, is the reason u mite see ppl cutting up there stock bumper to expose more of the coola..

one thing i always thort but, wouldnt with beta flow ud achieve more horsepower?... like thru 3" at 15psi wouldnt the flow produce slightly more hp than the flow from 2.5" ??.. or does the 2.5" act in no way restrictive?

Edited May 31, 2006 by BiRDY

[BezerkR32]

You loose airspeed with the larger pipe. it bottle necks when it reduces back down at the throttle body, and the larger area means more area to fill so can slightly increase lag. Your pipework should be the same size as your turbo outlet & throttle body. No step ups or reductions, just nice and smooth flow. in saying that the lag problem is easily sorted out if the pipework is shorter. If it is one of those cheap kits where the pipework runs up behind the radiator and then around into the throttle body, then no matter what pipe diameter, you have a large area to fill due to the pipe length, therfore increase in lag, and also heatsoke in the cooler pipe.

SMIC is more efficient but doesnt have the rice factor. There are kits where the cooler inlet and outlet are on the same side, this keeps the pipework shorter and cooler, therefore giving you a cooler charge even when you push a larger volume of air through at higher boost pressures. Do yourself a favour and spend the extra money on a kit that has been designed correctly.

the thickness of the cooler only really adds to lag unless u got mega horsepower, id say nething more than 75mm thickness is a waste for up to 20psi..

and yes a coola behind a bumper will not be as affective as a cooler with direct air flow... ie, is the reason u mite see ppl cutting up there stock bumper to expose more of the coola..

one thing i always thort but, wouldnt with beta flow ud achieve more horsepower?... like thru 3" at 15psi wouldnt the flow produce slightly more hp than the flow from 2.5" ??.. or does the 2.5" act in no way restrictive?

[LiQuid IcE]

hmm okay... so i guess if GTR coolers come with a thickness of 65mm thats the minimum i'd go