Originally Posted by Pangloss
Originally Posted by samchoi604
Clearly superior in what aspect? I wonder why BMW didn't put this superior engine in the 1M, 335is, Z4 35is.
Because people assume that having two turbos is better than having one.
I don't know that I would agree with Remonster that the N55 is superior to the N54, though. It might be, if for no other reason than the fact that engines generally improve over time and with proper attention, as is generally the case with BMW. But it's clearly no worse
, and it does include technologies that were not present in the N54.
I don't even think Remonster was wrong in saying that it was "not much of an upgrade". From a consumer perspective it's a total shrug. The only people who seem to have really noticed are enthusiasts and engineering awards committees like Ward's Auto.
I think the reason for the N55 is emissions quality and fuel economy. The N55 is cleaner burning and also more fuel efficient. They needed those two things because of EPA and CAFE standards that kick in in 2012. The cars that use the N54T engine are low enough volume enthusiast cars that they they can afford to put the less efficient engine in it and not hurt CAFE averages.
As evidence of how much more efficient the N55 is, especially in bigger cars, my girlfriend got her new F25 X3 with the N52 engine. The N55 powered model of the X3 actually got 3 MPG better than the N52!