Dewhel Universal Adjustable Billet Aluminum Turbo SQV SSQV blow Off Valves BOV (Black);

The Blow-Off valve (BOV) is a pressure relief device on the intake tract to prevent the turbo's compressor from going into surge. When the throttle is closed rapidly, the airflow is quickly reduced, causing flow instability and pressure fluctuations. Surge can eventually lead to thrust bearing failure due to the high loads associated with it. Blow-Off valves use a combination of manifold pressure signal and spring force to detect when the throttle is closed. When the throttle is closed rapidly, the BOV vents boost in the intake tract to atmosphere to relieve the pressure, helping to eliminate surge.