2.7T_M6

I agree with you too. Well said.

Tanner

... but they start to suck at higher boost levels. In the end, not really ideal for modders.

MTM will probably come out with something but cost $$$$ as usual

S4sposeur

in the process of extracting energy from the exhaust. Also, the turbo efficiency drops off markedly when the wastegate opens.

Modern superchargers are pretty darned efficient at low boost pressures. Some have special coatings on the compressor lobes to reduce friction.

The big efficiency gains were obtained by improving the non boost airflow and cutting out the compressor entirely when no boost is required.

The most efficient set up appears to be a small supercharger for low end boost and a turbo for high end, in series. BMW uses a small turbo in series with a large turbo for their excellent 3.0 twin turbo gas engine.

2.7T_M6

Just in case you didn't know, BMW is not the first to do this. I think it was also done in either the Nissan 300ZX or maybe it was the Toyota Supra. It must have been the inline 6 of the supra...I think

DeMOROlized

And latest rumor is S5 will also get the supercharged 3.0 V6 in MY10.

S4sposeur

with the K03 turbos on the B5 S4 I suspect that lowering the back pressure would simply move the turbine into an inefficent flow zone.

With my MTM chip and standard K03 turbos I would not go to the bother reducing back pressure. Practically speaking I cannot remain at full boost for long enough to realize any benefit.

The current set up, only the MTM and no other mods, seems to exploit the K03s pretty much to their practical limit. My guess is my car would reach 60 mph in around 5 seconds were I brave enough to drop the clutch. As it is, with non wheel spinning launches the car reaches redline in the lower two gears very, very quickly. At highway speeds the acceleration from 120 km/hr to 200 km/hr is electrifying. There's nowhere I know of around here to exploit any more acceleration without seriously jeopardizing my license.

2.7T_M6

My car is still a stock A6 2.7T and I find the first 2 gears very short. With the smaller S4 and a chip, it sounds like lots of fun. I guess you will have to take it to a track in order to really push the car.