I am probably going to go with the two RS4 intercoolers, because it will be cheaper and stealthy. I also won't have to mess up my bumper. I am just wondering if there will be a greater pressure drop with 2 intercoolers VS1 and any other considerations that I need to know. From my initial measurements, I should get about the same total cooling surface area as a FMIC, but the air must flow through an intercooler twice. I guess that given a turbo upgrade I can just increase the boost to counter the increased pressure loss. However, I will still have a slower boost onset.

The RS4 intercoolers are bigger than stock and the endtanks are aluminum vs rubber on the A4/S4.

All advice welcome.

Stock A4/S4 IC inlet/outlets are ~2 1/8" OD.

RS4 IC inlet/outlet comes in at ~2 5/8" +/- OD.

The RS4 will not fit right up. I don't know for sure. I think you may have to notch the frame rail or something like that. I'm not positive, but they have some sorta fitment issue IIRC.

stuff on that side. I had enough problems with just getting the IC tube in that spot when we put the evo fmic in the car.

I do think some notching of the bumper or frame was necessary though. I'm speaking of the S4 of course.

Not only is there virtually no room, but the pressure drop will make the whole project a waste of time. How about a rational approach?

Test the pressure drop and temperature delta for a RS4 in the car. Then compare that to a more efficient single core. Then look at the water injection and intercooler face spray systems...

If the IC(s) are working, there will always be pressure drop as cooler air is more dense than hot air. The pressure drop means that the IC(s) are working. You need to find both the pressure drop and the final intake temperature to make a valid comparison between the 2 styles.

pressure drop and temp. But your staement comes across absolutist.

The pressure drop is a differential in pressure that the turbo has to work against. You make less boost at the cylinder and the compressed air is even hotter because the turbo is working harder: making the final air tempreature at the head higher and the real boost at the turbo much higher. A lose/lose spiral.

Nobody said there should be NO pressure drop, just aim for the lowest possible drop (and pressure drop is NOT related to temperature exchange efficiency except at ludicrous extremes).

I will be building a FMIC. Time to locate a good core.