tboned

Does anyone here know if the "regular" 4.2 is technically close enough to the 4.2 FSI so that superchargers would be nearly interchangeable? With the APR supercharger for the "regular" 4.2 coming out soon (or not), I wonder if it would compatible if the S5 4.2 FSI in fairly short order....

Just wunderin'

tozoM8

It's going to be difficult to tweak it without $$$$.
I like your sig

ColoQuattro

I have supercharged a number of cars and the one thing that I have learned is that if you can put enough fuel in, keep the motor cool enough and make sure that your timing is in control dead on, you can supercharge anything and make it live reliably.
Whether you go with a positive displacement type of compressor or a centrifugal blower each will have its problems. For the Audi motor I am suprised that no one has tried a centrifugal blower. Its advantages would be no machining for the manifold and bottom end is good on the 4.2 cars so you can live with some lag, but plumbing and a tight fit would be a nightmare. The advantages to a positive displacement would be instant boost but you would have to fab a manifold.
Your other hurdle is your engine controls. How hard is it going to be to hack into the Audi CPU or do you go with a stand alone engine management system or even a piggyback management system.
With the already high compression and assuming that you only have one engine to work on one little mistake could be disterously expensive.
My suggestion is to pick up some literature on S/Cing, find a tuner that is willing and capabile of working with our car and pick a system. He/she will have to be a computer geek and a motor head and will need a 4 wheel chassis dyno at the same time.
My sincere belief is that the bolt on system available right now for the 4.2 is junk for the dollar.
JMHO Regards Coloquattro

Toxicity

heres some food for thought...
the MTM article that just popped up on the audi world main page a little while ago stated that they had specifically modified an S4 supercharger to fit on the RS4 although it did need some hoodmodification and other odds and ends it did work and was reliable enough to let the press have some fun in, which means some where in europe there is a roots style supercharger worth putting into your car.

As far as compression ratio goes i dont think a S4 has much to worry about as its cr isnt that much more than an A4's(10.5:1 vs 11:1) all u really need to do is figure out a way to get a good intercooler into it and keep boost levels relatively conservative, that said the 4.2 FSI outa the RS4 is an even higher compression ratio(12.5?) so its a little more tricky.

im with coloquattro though there should be more thought and effort put towards centrafugial blowers for the 4.2 engines especially as thier respective compression ratios would reduce the impact of lag in the blower and with the new B8 chassis having the motor pused further back there could be more room for the plmbing.

... personally i dream of one day doing an RS6 conversion to an S4...
Twin Turbo V8 WOO!