Originally Posted by Darth One
I more or less agree with the points on why the S65 is a better engine than the 3.4l Porsche f6, but it bears mentioning that Porsche provides more or less equal performance with less displacement, two less cylinders, and a heck of a lot better fuel economy.
if you step up to even the worst GT3 engine, the 3.6, it is better than the S65 in pretty much every category already mentioned, IMO. maybe we can quibble on reliability because of the RMS/IMS issue. and price, since the engine only comes in a car whose msrp is 2x that of the M3
the GT3 motor does achieve more power with less displacement, but that's not what has been debated. the Carrera motors are what we're talking about here since they're at least in the same stratosphere in terms of price, and in fact they don't provide any more hp/liter than the S65. even the FI motors that premiered in 2009 (two years after the S65 did) provide just slightly less hp/liter than the S65, and they do so even with the benefit of direct injection.
345 hp / 3.6L = 95.8 hp/liter
385 hp / 3.8L = 101.3 hp/liter
414 hp / 4.0L = 103.5 hp/liter
clearly the GT3RS 4.0's 125 hp per liter (500 total) is in an entirely different league and quite an achievement, but again, considering the price tag on that, it's not worth debating.
as I said in my first post, the Carrera motors do win in terms of fuel efficiency. however, that trade-off is both unsurprising and well worth it when you consider the improved throttle response and flatter torque curve of the S65 (which is due in part to the individual TB's).