Scheme 1603
Brief description of components
The following components are involved in the vacuum supply system
- Mechanical vacuum pump A mechanic vacuum pump is fitted to diesel engines and spark-ignition engines with Valvetronic. The vacuum pump is mechanically driven by the engine, e.g. via the exhaust camshaft.
- Suction-jet pump As a rule, the suction-jet pump boosts the vacuum in the inlet pipe.
- Electric vacuum pump On some engines, an electric vacuum pump is fitted for additional vacuum supply. In certain temporary operating situations, the vacuum in the inlet pipe may be too low. In such cases, the inlet pipe vacuum cannot be adequately boosted by the suction-jet pump. In these situations, the electric vacuum pump ensures that sufficient vacuum is available. Reason: After a cold start, an operating situation occurs in which there is very little inlet pipe vacuum due to the higher load. The electric vacuum pump is actuated for a certain time. This ensures that the brake is sufficiently boosted when maneuvering. After a cold start, the DME will actuate the electric vacuum pump once only for max. 60 seconds. The electric vacuum pump is actuated in the following situations: Engine-running signal from DME Coolant temperature below 60 °C The electric vacuum pump is a vane-cell pump.
- Throttle valve The throttle valve changes the cross-sectional area of the inlet pipe. This creates an inlet pipe vacuum behind the throttle valve, especially in overrun mode.
- DME or DDE: Digital engine electronics or digital diesel electronics The DME or DDE actuates the components needed for system functions (e.g. solenoid valves, electric switching valves, electropneumatic pressure converters).