Blow Off Valves

Blow off valves are used to prevent compressor surge, which occurs when you lift off the throttle of an un-vented, turbocharged engine. When the throttle plate closes, the high pressure air in the charge pipes is trapped, therefore it backs up into the compressor. The compressor wheel slows and may even stall, which in turn creates a fluttering air sound, known as compressor surge. Blow off valves relieve the damaging effects of compressor surge by allowing the compressed air to vent to atmosphere, making a distinct hissing/whooshing sound, or to be recirculated into the intake upstream of the compressor inlet. Whether you're building your STi for show, auto-x, road race, time attack or drag racing; you won't find a better source for your performance parts. Check out our blog for write-ups, how-to tips, installations, and dyno tuning results!