Originally Posted by footie
I understood that the MTM supercharged RS4 had it's CR reduced, was this not the case?
I think a good indicator of what is achievable as far as compression ratios and FI you should look at the Audi S6 and RS6 engine. In the S6 it's CR is 12.5:1 but with the RS6 it drops to 10.5:1, I would reckon much over this would cause problems long term and in any case you will have to lose that almighty rev range into the bargain.
Quote from here
The centerpiece of the MTM RS4 Clubsport package is the liquid-to-air intercooled, Lysolm-type, belt driven supercharger that resides directly underneath the carbon fiber bulge on the hood and feeds the car with 0.45 bar (6.5 psi) of fresh air. This cleverly designed package sits smack dab between the cylinder heads within the “V” of Audi’s 4.2 liter V8 and boosts power levels to a very impressive 535 horsepower and 428 ft-lbs of torque. The engine internals and compression ratio remains 100% stock.
Similar corroboration is available elsewhere on line.