The wastegate valve controls boost. It is operated by the vacuum actuator. Opening the valve stops boost and closing the valve generates boost. Boost levels are continuously monitored by the PCM.
In the operation, an increase in accelerator pedal sensor angle to boost detent, causes the pedal sensor to signal the PCM that engine load is increasing. At this point, the PCM closes the wastegate valve with the actuator and increases fuel flow to the injectors.
Closing the wastegate valve allows full exhaust gas flow into the turbine housing. As the gas enters the housing, it acts against the blades on the turbine impeller causing it to rotate.
Since the turbine and compressor impellers are fixed to the same shaft, the turbine impeller causes the compressor impeller to rotate as well.
Once the compressor impeller begins rotating, it draws fresh air into the compressor housing. The air is then compressed and pumped into the intake manifold. Fresh air source for the compressor section is through the air cleaner and related ducting.
A decrease in pedal sensor angle signals the PCM that boost can be reduced or stopped entirely. The PCM then opens the wastegate valve by reducing vacuum to the actuator. Once open, the wastegate causes exhaust gas to bypass the turbine housing and impeller.
