• Beginner’s Guide to Blow-Off Valves

    A blow-off valve is what gives a turbo car the popular “whoosh noise.” It is a device that releases high-pressure air into the atmosphere when you cease throttling, effectively safeguarding the turbocharger and engine from “surge loading” damage.

    How It Works

    When a car is running at high RPMs, a huge amount of air continuously enters the engine through the throttle and the turbo then attempts to compress it. As long as the throttle is open, the air moves along. When the system is pressurized, air tries to go back though the turbo and this is where the blow-off valve starts functioning. It lets off this compressed air into the atmosphere, thus preventing damage to the turbo. This action produces a variety of sounds that car enthusiasts generally love. Interestingly, some valves are made in a way that they enhance the sound. For example, some are fitted with trumpets-shaped outlets to give a better sound.

    HKS Super Sequential Blowoff Valve (SSQV)

    HKS designed the first Sequential Blow-Off Valve in 1994. This pull-type valve was engineered in such a way that it was stable no matter how much boost or pressure is present. Its unique pull-type sequential valve structure was an auto lover’s delight. Now, the latest Super SQV 3 has a nickel-plated, die-cast metal secondary valve, and a stainless steel C-Clip and spring. To prevent duplication, the blow off valve has a holographic HKS logo on its back; in addition to logos on it body. This valve is stable, and it doesn’t leak with high pressure, nor is it ever under vacuum. This is how the SSQV works. It has two valves: primary and secondary. The primary valve opens initially for light pressure, followed by the secondary valve under high pressure conditions. The HKS SSQV can be used for custom applications as well. Along with its functions, this valve has a powerful blow-off sound and appealing appearance.

    Subaru Impreza WRX/STI

    If you have a Subaru Impreza WRX/STI, it is necessary to know that it has unique blow off valve requirements. APS designed ones specifically for this model. With this twin-vent valve, the turbo response is better and improved. Moreover, it increases the durability of the turbocharger. This APS valve has a 30-micron hard anodized, T6 billet aluminum body, low friction bronze piston and all stainless steel hardware.

    Now that you know the basics, let’s explore how to install this incredibly useful gadget on your car.


    A blow off valve install can be a fairly easy process depending on your car but by doing so you can maximize your engines performance while also extending its life.

    Always disconnect and remove the battery prior to installing a blow off valve. While you may be able to complete the installation without doing so, it is always an extremely good idea to disconnect the battery to any work inside the engine compartment for your safety.

    An auto repair manual is extremely helpful, especially in locating your existing recirculating valve, which is replaced by your new blow off valve.

    Any vehicle with a mass airflow sensor may require additional work to your engine control unit. Most of these aftermarket ECU units can be quickly installed to assist in ensuring your engine runs properly after the modification.

    Of course, installing any aftermarket device, including blow-off valves, may void warranties on your vehicle; something you should be aware of ahead of time.

    Installing this on an unmodified, stock turbo car will be minimal at best. Also, engine bog is common between gears; it means the valve is working properly.

    Blow-off valves really enhance the performance of your vehicle. Make sure you have the best one for your car, based on design and output. A dual drive blow-off valve is ideal for fast cars, as they respond to all kinds of pressure situations. One thing to keep in mind is to get a valve that has a urethane gasket as it ensures a tight seal.