Originally Posted by Uli_HH
It is almost impossible, that an I6 based on the N55 can attain an redline of 8.000rpm ... the only BMW turbo engine which would be able to do this, is an S63Tü based V6 - because of his square cylinder design.
This engine, an 3.2ltr.V6 BiTurbo has run into an endurance test on the engine test bench with this 8.000rpm ... which has probably led to the rumors of a redline of 8.000rpm for the new M3/M4 engine
But the probably next M3/M4 engine, an 3.0ltr.I6 TriTurbo will almost certainly have a redline of ~ 7.000rpm.
Considering that the S54 was undersquare and spun to 8000RPM there is no reason that the "S55" couldn't...... The reason it won't spin that high is because it won't have to since the turbos will allow peak power at a lower RPM than traditional NA M engines.