P07.05-2052-12
1 Boost pressure regulator valve (Wastegate)
2 Control rod
3 Vacuum cell
Y77 Wastegate valve
Location
The wastegate valve is located at the top of the coolant thermostat housing.
Task
The wastegate valve controls the boost pressure of the turbocharger.
Function
The vacuum cell actuates the boost pressure control valve via a control rod. If the boost pressure is too low, the vacuum cell closes the boost pressure control valve via spring force, the bypass is closed and the entire exhaust gas volume drives the turbine wheel. As the exhaust gas quantity increases, the turbine wheel speed increases and thus the boost pressure. The rising boost pressure affects the diaphragm of the vacuum cell via the wastegate valve.
The motor electronics control unit N3/10) calculates the boost pressure and actuates the wastegate valve accordingly. This opens the boost pressure control valve via the vacuum cell. If the bypass is opened, part of the exhaust gas volume can bypass the turbine wheel. Thus the speed of the turbine wheel is reduced and therefore the boost pressure.
In the event of failure of the wastegate valve, the vacuum cell opens the boost pressure control valve at a boost pressure of 0.6 bar.