Turbocharger Blow-Off & Diverter Valves

Blow-off and diverter valves have always been popular upgrades for a turbo engine. However, not all car enthusiasts know why they are so important, and what the difference between a blow-off and diverter (also called bypass or recirculating) valve is. So let’s make things clear. Your turbocharger compresses air and forces it to the engine. This allows more air to enter the cylinders, which results in stronger combustion and increased horsepower. The high-pressure compressed air enters the engine when the throttle plate is open. However, when the throttle plate closes, this air has to be released; otherwise, the pressure in turbo piping will increase dramatically causing the air to move in the opposite direction. This can compromise vehicle performance and damage your turbocharger, engine and other vital vehicle parts.

Blow-off and diverter valves prevent this from happening by letting the air escape from the tubing. Once the throttle closes, the manifold pressure instantly drops below the atmospheric pressure. The valves sense this change and open to release the air. Blow-off and diverter valves do the same job but differ in the way they do it. Diverter valves recirculate the air back into the intake while blow-off valves vent it to the atmosphere. Since diverter (bypass) valves are better at keeping the pressure consistent, they come standard on most modern turbocharged vehicles. Blow-off valves create an attention-grabbing chuffing sound and are typically an aftermarket modification. On our website, you’ll find an extensive variety of both blow-off and bypass valves that are made using high-strength materials to offer uncompromising performance and reliability.

When choosing between a blow-off or a diverter valve, don’t forget to consider several important factors. First of all, remember that it’s not recommended to install a blow-off valve if you have a factory ECU and (MAF) sensor. The sensor calculates the amount of air that enters the engine and sends these data to the ECU so the ECU can determine the amount of fuel needed for a balanced air-fuel mixture. The blow-off valve vents the air after it has been calculated by the MAF sensor. But the control unit injects excess fuel taking into account the readings from the MAF sensor. This will eventually result in a rich mixture. To get a louder sound without compromising performance, choose a dual port blow-off valve that releases half of the air to the atmosphere while recirculating the other half back to the air intake. However, if you use an aftermarket ECU, you can upgrade to whatever valve you want.

Factory diverter (bypass) valves cope with the pressure pretty well, so there’s no obvious reason to upgrade them when you have a factory or low-tuned setup. However, they tend to leak under boost levels that are much higher than factory ones (usually 25 psi or more). In this case, you can opt for a high-flow bypass valve that can flow a larger amount of air without any airflow issues. But if you start making mods that are beyond the capabilities of the diverter valve, for instance running an 800-horsepower engine, blow-off valves are the only solution. So as you can see, your choice will depend on your performance goals and the type of setup you’re running.