The TurboXS Blow Off Valve - Type S is designed to release compressor pressure surge caused by changing gears or backing off the throttle quickly. This valve is an extremely important part of any turbo system allowing quick boost response and greatly increasing the life of a turbocharger. The BOV Type S is designed for small to medium sized turbo charged engines running from 5-15 psi boost, however, when properly installed and adjusted, there is no limit to the maximum boost pressure this unit can hold.