If the throttle is closed while the engine is overrunning, back pressure will develop in the compressor housing due to the constant pressurization. This back pressure significantly reduces the speed of the compressor impeller, with the ultimate result of reduced boost pressure and increased turbine lag. To avoid this, the turbocharger shunt air valve is opened by an electric actuator. The valve opens a bypass pipe that allows compressed air to rotate through the compressor blades back to the intake side of the compressor loop. In this way, the required turbine speed is maintained. When the throttle opens, the turbocharger shunt air valve closes and the booster pressure is immediately available. This Part Fits the Following Vehicles Make Model Submodel Engine Year Chasis MINI All Cooper S All All R58 MINI All Cooper S All All R59 MINI All John Cooper Work All All R56 MINI All John Cooper Work All All R57 MINI All John Cooper Work Clubman All All R55 MINI All John Cooper Works All All R56 MINI All John Cooper Works All All R57 MINI All John Cooper Works All All R58 MINI All John Cooper Works All All R59 MINI All John Cooper Works All All R60 MINI All John Cooper Works All All R61 MINI All John Cooper Works Clubman All All R55 MINI All John Cooper Works WC50 All All R56 MINI All S All All R56 MINI All S All All R57 MINI All S All All R60 MINI All S All All R61 MINI All S ALL4 All All R60 MINI All S ALL4 All All R61 MINI All S Clubman All All R55