Originally Posted by claykin
I've been told my BMW mechanics to think of the N55 as a cost reduced version of the N54. BMW simplified the design, cut out some of the high end components (i.e. piezo fuel injectors, dual independent turbos) and traded off raw performance for ability to better control fuel consumption.
N55 still uses HPFP, but design has been improved. N54's with latest HPFP should no longer experience high failure rates. My E90 MSport is still on its original fuel pump. The 2010 DME reprogram is said to address this issue.
Yes, the N55 is a cheap, fuel efficient replacement for the N54, which should be coming out of the factory for 350-390HP applications. The N55 is well suited for the 300-350HP range. BMW is so cheap.
Which is why I avoid the 35i- engines in the F30 and F10.. they are just trying to wring out as much profit as they can from unknowledgeable consumers.
The N54 when it came out on the e90 was a good buy, severely underrated and lots of potential. The current N55s barely squeak by in my book.
The gap with the f30 M3 should be much larger, hence waiting for the M3 a better idea especially since the current f30 N55 should be updated quickly.