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I've just fitted a new lambda sensor and I have a meter showing me the fuel mixture as i can adjust it with my Apexi. I attached a couple of pictures showing the 2 brackets I had made to mount the charger. It was the inlet and outlet manifolds to the charger that were more complex.
I have last night been fiddling with the charger. I think after all that the charger is okay, both ends have oil in the gear chambers and it does turn quite smoothly when turned by hand, more so now its been run for a long while on the car. I think its definately the air you can hear being pumped out that's causing the noise and not a mechanical noise. I have reseached on the web and many people complain of supercharger noise even on brand new cars. Maybe I'm expecting too much, after having a whisper quiet Merc I'll have to accept the blower will make it noisy. I may add an additional mechanical by-pass valve to open on closed and slightly open throttle. The Bosch bypass valve I have has 22mm bore but when open under vacuum conditions it only fully opens 5mm. This equates into an opening area of 345mmsq against the cross section area of the pipe of 380mmsq. I believe the 2.7 S4 Audi's have 2 of these valves so maybe 1 just isn't enough to by-pass the air on idle on my 2.8. This may reduce noise at idle and the popping noise I'm getting as I close the throttle. I'll also try moving the MAF sensor back to before the blower which is where I had it originally but the engine wouldn't idle. I'm going to bolt the whole thing back on and try connecting the original air box just with the bonnet open to see if the noise reduces. If so I might make a new air box with a panel filter and ditch the K&N; I have read these are the worst filters for transmitting noise.
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