Designed for high performance, the BOV17 - Type H relieves 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 H provides greater venting flow than the Type S and is designed for turbo charged engines running 10 psi or higher boost. There is no limit to the maximum boost pressure this unit can hold.