Adjustable relief pressure and flow control makes fine-tuning on the fly simple and quick.

With large 1.225" inlets and outlets, the PERRIN Blow Off Valve is sized perfectly to relieve any amount of boost pressure without fear of compressor surge. Don’t be fooled by giant oversized blow off valves, these inlet and outlet sizes were chosen to ensure the perfect balance of flow and to maintain boost in your system, without ruining response by dumping too much boost.

The PERRIN Blow Off Valve cap features adjustable spring tension, which allows for an adjustment when the blow off valve vents. A looser setting will make it act smooth and more like stock. Setting it harder will cause it to vent later and with significantly increased boost levels. This adjustment is important in maintaining air within the boost system without reducing turbo response.

The unique design allows you to control the volume of air released when the blow off valve vents. Adjusting the volume of air helps maintain the perfect amount of boost in your system during shifts without causing compressor surge. Venting too little can damage the turbo, venting too much air can make the throttle less responsive. This adjustment is independent of the relief pressure allowing for a totally customizable blow off valve.

It is vital that a blow off valve for your WRX/STI recirculates the air back to the intake track to maintain proper air-fuel ratio and driveability between shifts. While this can be set up as a vent-to-atmosphere style blow off valve, we only recommend that on cars running aftermarket Speed Density type tuning (cars without mass airflow sensor).

The PERRIN Blow Off Valve requires very little maintenance but when needed, it's very easy and quick to disassemble. Two O-rings are used to seal vital components from the elements making for extended time between service intervals. There are no special tools required and maintenance can be performed without removing the blow off valve from the vehicle.

Included with every PERRIN Blow Off Valve are the necessary components to make this a direct bolt-on for your WRX/STI. Each blow off valve is pre-set out of the box to work perfectly with every application, so no adjustment required.

The PERRIN Blow Off Valve cap, piston & flange are all CNC machined from 6061 Billet Aluminum. The PERRIN Blow Off Valve body is CNC machined from a single block of aluminum. This makes for a clean look that reduces potential failure points and leaks without additional parts.

The PERRIN Blow Off Valve comes in either a black or red anodized finish. The anodizing keeps the blow off valve looking great during its lifespan. The blow off valve body and cap are pad printed in vibrant lettering to make it easier to read.