|
Another difference is that if the N51 is coupled with an automatic transmission, the transmission has a N51-specific mode of operation. That is, during the engine warm-up phase, the transmission will automaticlly shift to neutral when the vehicle comes to a stop. When you release the brake pedal, the transmission shifts back into gear. This behavior reduces load on the engine when it's cold, further reducing emissions. Once the engine has sufficiently warmed up, the transmission behaves like any other automatic typically does.
Regarding the power difference, there was a N51 dyno posted on this site (or maybe it was E90post) recently and it showed that peak horsepower and torque numbers are the same, though the N51 has slightly more area under the curve in the low- to mid-range. This is undoubtedly due to the DISA 3-stage intake manifold that the N52 lacks. The trade-off is that you can feel the changeover points for the intake manifold on the N51 (though they are slight) as engine speed climbs, whereas the N52 is very linear from idle to redline.
Also, it's been noted on this site not too far in the past that some of the N52s have the underbody catalysts, also. This is because there are actually two versions of the N52, LEV and ULEV, with the ULEV having the underbody cats.
|