Belt Drive
One of the most outstanding characteristics of the E72 is driving in pure electric mode. Functions like hydraulic steering and air conditioning are also to be available in this case. Since the combustion engine does not run during this operating condition, it cannot drive the power steering pump and the air conditioning compressor.
Consequently, both of these systems are operated electrically and omitted from the belt drive. Since the E72 also has no conventional alternator on the engine, this is also omitted from the belt drive.
Thus the belt drive is designed with the highest possible simplicity. Only the coolant pump required for the electric machines is driven. A tensioning pulley is not required since an elastomer belt is used, which is installed using the "turret clamping system" known since the N63. The elastomer belt is, as usual, a poly-V belt with 4 ribs.