Variable valve timing in itself is not new, but there is much more to what BMW has accomplished with its Shift Cam system than combining two different engine characters in one. On high load, throttles are nearly open and rpm is rising. At higher revs, intake velocity is also high, carrying lots of kinetic energy into the cylinders to produce the strong turbulence that accelerates flame speed, producing quick, efficient combustion. But at middle and lower revs, intake velocity falls because the engine’s pistons move more slowly. This causes flame speed to slow, increasing heat loss and reducing torque. To prevent this, BMW’s Shift Cam system gives its part-load cam profiles less lift, recovering much of the intake velocity that would otherwise be lost at lower loads.