Ok, I want a FMIC for my car - a 2000 A4 1.8TQM, currently a chipped K03 turbo - and I have some goals for it beyond pure performance. I want to keep my stock A4 front bumper cover; I hate the looks of a FMIC on a car; and lastly, I don't care whether I keep the stock cross-pipe intact or not.

Right now, I'm most interested in the Race Tec Z-flow FMIC that SPP is selling. It seems to meet my cosmetic concerns as much as any other intercooler on the market, and has gotten some great reviews here on AW. Folks seem to rave about the quality of the piping, the Z-flow design, and that the bulk of it is exposed to airflow (not blocked by body work.)

My concern is that the core on this FMIC is on the small side. According to the DUH engineering website, it's 18x6x2 inches (216 cubic inches,) which is only about 24% bigger than the stock SMIC (9.5x6.8x2.7 = 174.42 cubic inches.) So, presuming that the Race Tec is better than other aftermarket options -- which certainly hasn't been proven, but work with me -- what makes it able to function as well as other larger aftermarket intercoolers? Or will it simply not able to function as well as bigger cores, intercooling being 99% dependent on the size of the core? Am I crazy for considering the Z-flow when the other SPP FMIC (20x10.5x1.8) is 116% larger than stock, and also fits behind my stock bumper cover?

So here's what I can come up with as possible explanations of why such a smallish FMIC could work really well. I'm sure all of these things are factors in an intercooler's performance, but I just don't have the experience and knowledge to know if they are significant enough to make up for size in any meaningful manner.

1. Exposure to the wind. If the smaller core is 100% exposed to the incoming wind, and a bigger one is 30% blocked by body work, then this would favor the smaller core.

2. Greater internal surface area for a given core volume.

3. Better turbulant properties inside the core.

4. Many short pathways through the core, rather than fewer but longer paths. I read somewhere that this leads to lower pressure drop across the intercooler.

5. Dimensionally, wouldn't a thinner core with greater frontal area be more effective than a thicker core of the exact same volume? My logic is that the cooling air heats up as it passes through the core, so by the time it gets to the back of a thick core the efficiency might be reduced. I'm flat out guessing here, if you can't tell..

6. Superior piping design. Shorter, wider, smoother, straighter, more rigid pipes?? I'm really not sure what "superior" means here, but I'm positive there must be good and bad ways of doing it!

I guess that's about all I can think of. Can anybody offer some more insight, or point me to some good information to understand why it might be reasonable to choose the intercooler that's only 24% bigger than stock, rather than the one that's 116% bigger? Thanks..

 

Hey,

I don't think this comment add much value to your questions but... I seem to have a thermal management issue with my car. I've been looking around for an aftermarket IC myself. Two different shops (Boston area) have told me that aftermarket side-mount is actually more effective since the front-mount has the radiator right behind it to block the air from flowing through the IC. One shop claims it actually ran numbers to come to that conclusion. Take it for what its worth since I haven't actually seen the numbers.

 

a little trimming involved to make it fit, but stealthy and it works. THe RS4 and racetek (as well as stock) flow vertically. So they can get away with a smaller core. Basically isnce there ar ea lot of short rows, the core will work well.

 

Which shops? Presumably one of them is Shine - I know you work with them occasionally.

 

I hadn't even considered that they might be effective; it seems counterintuitive that the FMIC wouldn't have a big airflow advantage, but I shouldn't discount Audi engineering if I don't understand it. The RS4 intercooler is smaller than the A4 one though too.

Hopefully GJaime will chime in...and off I go to do some more S'ing of TFA :-)

 

With all the million$ in R&D, what did Audi choose?

 

One that's sufficient for the meagre flow and power output of the car in stock form?

 

Clears throat... S4, RS4, RS6, 225 TT, LeMans, ect. Please try again.

 

Most of the Audi IC's use a GRP end tank, which is CRIMPED and CLIPPED on to the aluminum core, sealed by a rubber "o-ring". They cannot handle higher levels of boos. Most pop by 19psi or so. The old Dual Pass setups are even worse, they go at pretty much anything above 10-12psi.

Also, they provide a factory acceptable efficiency for the given packaging restraints, which are generally very tight.

Just by chaning an old dual pass IC to a single pass, you get a colder charge air temperature, and less lag.

Switching a 225 TTq over from two seperate IC's to a single FMIC of the same total volume would do the same (the 225hp TTq I feel has too much lag, the dual IC's package very well, but result in poor transient response IMO).

 

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