The valvetrain on the N52 introduced in 2006, used 5 mm valve stems on both
the intake and exhaust. To
increase durability, the exhaust valve stems were increased to 6 mm from 6/06
production.
All of the new NG6 engine have adopted the 6 mm valve stem for the exhaust, the
intake stem remains at
As far as the physical appearance and dimensions, the crankcase on the N54 is
the same as the N52. The main
change is in the materials, the N54 uses an all aluminum alloy crankcase. There
is also cast iron cylinder liners
similar to the previous M54 engine.
The reason for using the all aluminum c