Air Pressure Management APM 

MAN Air Pressure Management (APM) helps to save fuel by reducing the engine's output to auxiliary equipment.
With APM, the continually running standard compressor with rigid drive is replaced by a new compressor system that can be switched off. The multiple disc clutch automatically cuts the power flow when the air tanks reach the shut-off pressure, and the compressor comes to a standstill. When compressed air is taken from the tanks, the clutch closes -- the compressor then resumes work until the shut-off pressure is reached once more, then stops once again. The on-time of the compressor is therefore reduced by 90 % in the long haul segment. Stopping the compressor from running under no load achieves fuel savings of 0.5 l over 100 km. In addition to reduced component wear due to this switching off, the system also lowers noise emissions, as the loud blowing out by the compressor while it runs under no load is eliminated.