The Subaru Impreza WRX/STI has unique blow off valve requirements particularly when fitted with a large turbocharger. A blow off valve is a device that releases pressure from the turbocharger when the throttle is released.

APS designed the APS high volume twin vent blow off valve specifically for the Subaru Impreza WRX/STI. It is an ideal enhancement for applications using the standard turbocharger up to large 600 hp units.


With its huge capacity the APS blow off valve gives you the ultimate in turbocharger durability and improved turbo response particularly during gear changes. A mammoth 1.375" (34 mm) internal bore size delivers huge capacity and at full piston travel, all ports are fully exposed for maximum blow off volume.

The APS twin vent BOV features 30 micron hard anodized, T6 billet aluminium body, low friction bronze piston, all stainless steel hardware including spring and Viton 'O' rings.

The large primary vent is designed to plumb back to the standard entry point which ensures the best driveability during cruise conditions and cures the problems seen with after market external single venting blow off valves.

And for large turbochargers running high boost pressure levels, the APS twin vent blow off valve continues to vent through to the second stage port.

Fine adjustment to blow off valve operation can be performed through the actuation adjustment screw for optimum configuration.

APS BOV development:

We are often asked why we developed our own blow off valve when there are so many on the market. Quite frankly APS had not found a blow off valve for the WRX/STI that offered the level of performance required.

With a large turbocharger, releasing pressure from the turbine compressor wheel when the throttle is snapped shut is critical not only for turbocharger response, but for turbocharger longevity. A huge volume of air must be passed through the blow off valve as soon as the throttle is closed.

Most blow off valves have limitations in their design that inhibit the level of performance we demand. Piston/bore diameter and venting ports are often too small and surprisingly, most will not fully expose the exhaust ports when fully opened.

Ultimately, the need for a truly high performance blow off valve specifically designed for the WRX/STI needed to be satisfied.

*Please Call for Best Pricing - 1-480-966-3040*