Blow Off Valves: History, Function, and Why You Need One

If you’ve ever heard a sharp “psshh” when a turbocharged car changes gears, you’ve experienced a blow off valve (BOV) in action. This small but crucial component plays a big role in turbocharged performance, both in protecting your engine and enhancing your driving experience.

A Brief History of the Blow Off Valve

Blow off valves became more common in the 1980s and 1990s as turbocharging spread from race cars to production vehicles. Originally, they were designed primarily for performance applications, where turbo lag and compressor surge could limit power and reliability. As automakers refined forced induction systems, the BOV became a standard tool to manage turbo pressure between shifts.

How It Works

When you lift your foot off the throttle in a turbocharged car, the throttle plate closes, but the turbo is still spinning and compressing air. Without a way to release that built-up pressure, it can bounce back into the turbo, causing compressor surge — a damaging condition over time. The BOV opens to vent excess pressure, keeping your turbo safe and your shifts smooth.

Why You Need One

Whether you’re building a performance car or maintaining a factory turbo system, a blow off valve offers key benefits:

  • Protects your turbocharger from damage caused by pressure spikes.

  • Improves throttle response by keeping turbo speed up between shifts.

  • Reduces wear on your engine’s intake system.

  • Adds a signature sound that enthusiasts love.

The Bottom Line

From its roots in motorsport to its everyday role in modern turbocharged vehicles, the blow off valve is a small investment with big payoffs. It keeps your turbo healthy, your power delivery consistent, and your driving experience that much more exciting — all while giving you that unmistakable “psshh” soundtrack.