Using aluminum hats on the steel brake discs, four - piston brake calipers that require less structural bracing, and smaller wheelhubs and suspension knuckles, BMW reduced unsprung weight by 15
percent over the outgoing car.
BMW also claims the mill provides a 25
percent improvement in fuel economy
over the
outgoing V10 thanks to the inclusion of features such as brake - energy recuperation, an alternator that disengages under acceleration and an automatic stop / start function — all part of the German
car maker's EfficientDynamics initiative.