Brake Booster on Cayenne S Hybrid

Brake Booster On Cayenne S Hybrid

The Cayenne S Hybrid uses Power assistance malfunction an additional electric vacuum pump, which can supply the required brake pressure even when the engine is switched off. This is the case when the Cayenne S Hybrid drives on electric power only, coasts or is in Auto Start Stop mode.

Design







Schematic diagram







Function

When the combustion engine is in operation, the vacuum for the brake booster is supplied by the mechanical vacuum pump (1). When the combustion engine is switched off, the electric vacuum pump is switched on as required depending on the vacuum conditions.

The pressure sensors installed in the vacuum line and DME control unit record the current pressure in the brake booster as well as atmospheric pressure. If the vacuum detected in the brake booster is too low, the DME control unit switches on the vacuum pump via a relay. The vacuum range is between 550 mbar and >750 mbar.

Diagnostics







Within the framework of diagnosis, the vacuum supply is continuously checked and appropriate measures are initiated if necessary.

If, for example, the vacuum level does not increase by at least 200 mbar within 10 seconds despite activation of the vacuum pump, the combustion engine is not switched off again. If the vehicle is driving in electric mode, the combustion engine is switched on again immediately. In this situation, the yellow Hybrid warning lamp is switched on.

If the required vacuum is not reached again (e.g. as a result of leakage), the red brake warning light is switched on.