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Charging pressure control

The charging pressure of the exhaust turbocharger is controlled by the DME by means of a bypass valve (wastegate valve). The bypass valves are activated via the electropneumatic pressure transducer by the DME (map-controlled).

In addition to the bypass valves, 2 blow off valves are fitted. Without the compressor bypass valves the turbochargers would have to work against the backpressure induced by the closed throttle valve. When the throttle valve closes the increase in manifold pressure causes the compressor bypass valves to open. When opened, the blow off valves connect the inlet side of the compressor with the exhaust side of the compressor. This prevents excessive ram pressure.

Fig 1: Variable Camshaft Control System Diagram
G09871677Courtesy of BMW OF NORTH AMERICA, INC.
Item Explanation
1 Electropneumatic pressure converter (for adjusting the bypass valve on the exhaust turbocharger for cylinders 4 to 6), activated by the DME
2 Electropneumatic pressure converter (for adjusting the bypass valve on the exhaust turbocharger for cylinders 1 to 3), activated by the DME
3 Engine ventilation heating
4 Intake-manifold pressure sensor
5 Intake air temperature sensor
6 Electromotive throttle actuator
7 Blow-off valves, controlled via the intake pipe vacuum
8 Intake silencer
9 Charging pressure sensor
10 Engine
11 Bypass valves (wastegate valves)
12 Charge air cooler
13 Exhaust turbocharger
14 Non-return valve with pressure limitation (for engine ventilation in the inlet ports)
15 Non-return valve to the fresh air pipe (for engine ventilation)