Intelligent energy management in the new BMW 3-Series is further enhanced by the ancillary units, which consume significantly less energy compared with conventional systems. Examples include the on-demand coolant pump, the electronically controlled oil pump and the electromechanical steering system, which only consumes electric power when steering assistance is actually required. The special air conditioning compressor featured on many of the sports sedan models works on the same principle. As soon as the driver switches the air conditioning off, the belt drive to the compressor is disconnected by a magnetic clutch, to minimise power drain.