Thoughts on E63 TT
"Specifically, for a given displacement you have to make power with RPM on a naturally aspirated engine. If you have a turbocharger, you make power with boost, and everything being equal, at lower RPM, with less friction and with better fuel economy."
Engine theory is great, but in practice you aren't going to improve fuel economy going to an FI setup. If you're in boost you're dumping fuel, especially on a high compression motor that was designed NA (re: 6.2L AMG motor in the 63) - you'll tune it rich to keep it from melting parts, which will reduce fuel economy whenever the engine sees boost, even at part throttle.
Its not too difficult to fix though - get slightly shorter & lighter conrods slap them in, then you are free to turn up the wick on the blowers ... which ever you choose. Ok so you lose some go low down - but top end will be outrageous.




I know what you are saying but it's not theory. 99% of the people 99% of the time will drive the car at it's peak or very close to it's peak torque but there are times the engine will be driven very hard. Yes, those times the car will see reduced fuel mileage and increased engine wear.
Tuning an engine overly rich is a band-aid for a problem caused by an inefficient intercooler system. The E55 is a perfect example of a car with an inefficient or lacking intercooler design. You will see the overly rich tuning by most companies in an effort to cool the intake charge on the E55 when boost levels are increased past stock.



