Originally Posted by grimlock
"So the N55 was an excellent match, there was no need to use the N54. Especially seeing as the N55 sets standards in the segment in terms of fuel consumption and CO2 emissions."
Admission the change from N54 to N55 was economy related, that the N54 with two separate turbos is better?
Obviously. In fact, this was well known before. When BMW M opted for the N54 for the 1 series M coupe development and not for the N55 both engineers and executives made clear statements about N54 being more suitable for extra power and torque and for further tuning possibilites, there were also rumours that the N54 wouldn't be able to meet forthcoming tighter emissions standarts in various markets. Plus, the two turbo set up of N54 gives less turbo lag. N55 is really an emissions and consumption oriented unit despite similar or identical output.