A blowoff valve (BOV), bypass valve or dump valve is a pressure release system present in most turbocharged engines. Its purpose is to prevent compressor surge, and reduce wear on the turbocharger and engine. Blowoff valves relieve the damaging effects of compressor "surge loading" by allowing the compressed air to vent to the atmosphere, making a distinct hissing sound, or recirculate into the intake upstream of the compressor inlet.
The Active Autowerke Blow Off Valve is a pull-type blow off valve suited for high horsepower applications. It is used extensively throughout the Active Autowerke product line both for turbocharging and supercharging. Constructed from an all aluminum cast body, with a large single stage, steel pull-type valve to handle the extreme pressure and airflow discharge volume that is associated with high boost / horsepower applications. The BOV is engineered for up to 43psi of boost and can function precisely on BMWs producing more than the 500 horsepower range.