Boost pressure control

The engine management controls the boost pressure with the wastegate valve at the turbocharger. An electropneumatic pressure converter (vacuum solenoid) receives the signals from the engine management and supplies vacuum to open the wastegate valve when the specified maximum boost pressure is reached.

A diverter valve is installed on the compressor housing of the turbocharger. It connects the pressure side to the inlet side of the induction system and is controlled directly by the engine management. The diverter valve eliminates undesirable peaks in the boost pressure that can occur when the throttle valve is quickly closed. Therefore it has a decisive influence on the engine acoustics while protecting the turbocharger and its related components.

A pressure wave is built up from the throttle valve to the turbocharger compressor wheel when the throttle valve is closed. This pressure wave acts against the throttle plate and the compressor blades pressing them against the bearings. The diverter valve reduces this pressure wave and thus the load on these components by "diverting" air pressure from the pressure side to the suction side of the compressor housing. This also maintains the turbocharger spooled (up to speed) for the next acceleration and reduces turbo lag.