Secondary Air System

Secondary Air System





For use in the (E85)Z4) Z4, the M54 secondary air pump has a high output supply rate (45 kg/hour).
The electrically driven secondary air pump is mounted to the body in the engine compartment (in the area of the right-hand strut tower). To draw in secondary air, the SLP has an integrated air filter element. The air filter element is maintenance-free during the service life of the vehicle.
After the engine is started, the ECM activates the secondary air pump relay to provide power to the secondary air pump. It remains on until the engine has taken in a certain amount of air. The ON period may be a maximum of 90 seconds and depends on the following engine operating conditions:
^ Coolant temperature (from -10°C to approximately 60°C)
^ Air mass
^ Engine speed
The secondary air valve is mounted to the side of the cylinder head. The SLV is opened by the pressure generated by the secondary air pump. The secondary air is led through a pipe to the secondary air ducts. The SLV closes as soon as the secondary air pump switches off, preventing emission "back flow" to the secondary air pump.