I have found 2.5 and 2.75 thick intercoolers. (2.75" has nominally 10% more air volume and similarly more heat exchanger area).

All are 20" wide and 6 high (don't need more for my mild turbo upgrade <20 psi).

I don't mind some trimming of the bumper plastic, but do not want to cut into the bumper reinforcement.

Will both fit with no problems?

Also: I don't know what the factory pipe diameter (running across the front) is, but it looks very small.

Since it is quite a bit of length, I plan to use only 2.0 diameter for the tubing (more compressible air volume = more turbo lag).
2.25"=+26% air, 2.5"=+56%, 2.75"=+89%, 3.0"=+125%)

 

2.75" tick is going to be a tight fit so you might want to stick with the 2.0".

What you can always do is do a mock up of the FMIC in those sizes to see if it will fit behind the stock bumper. The fitment spots will be down low and where the end tanks will be since the stock bumper cuts in and back making the space much smaller then in the center.

Even if you have to cut the bumper bar you only have to cut the bottom lip to allow the fmic to tuck up behind it.

 

You mean 2.5 thick (instead of 2.75); those are the only choices I have (you mentioned 2.0 above).

 

Yeah sorry about that, 2.5". Most of the kits out there for the stock bumper use a 2" thick fmic.

 

I'm planning on buying a rs4 body kit (including front bumper) so how thick do you think I can go with a FMIC? reccomended dimensions?

 

if i remember correctly, i believe the rs4 bumper has even less room than the a4 or s4 bumper... but im sure someone else will chime in.

 

RS for has more room then the stock B5 A4 bumper but less room then the B5 S4 bumper. The sections between the center opening and the outer opens need to be cut to allow the pipes to get by. Out of all the bumpers for the B5 the S4 bumper has the largest area behind it.

 

so how big of an FMIC can I fit with the rs4 bumper, cutting it as much as possible? is there a big difference in room between the s4 and rs4 bumper or is it a small difference?

 

There is a good difference. Best way to see this is to search for B5 S4's that have a FMIC kit on them with the S4 bumper and the RS4 bumper. It is a tighter fit for the FMIC on a RS4 bumper then a S4 bumper and this is because the S4 bumper is more smoother on the front and at the openings and the RS4 has lips that go back into the openings.

 

thanks man, do you think this core would fit behind an S4 bumper? Garrett Intercooler Core: 24" x 12" x 3.5"