Blow off Valves

Everything You Need to Know About Blow Off Valves

Introduction: Blow Off Valves, also known as Pop Off Valves or Drain Valves, are essential components in the world of automotive tuning. Not only are they recognized by various names, but they are also celebrated for their distinctive hissing sound, a hallmark for any car enthusiast. In this article, we will delve into the intricacies of these systems, understanding what a Blow Off Valve is, its role in preventing turbo lag, and much more.

What Is a Blow Off Valve?

Apart from its nicknames, the Blow Off Valve is commonly referred to as the "hissing thing," aptly describing the noise it generates when releasing excess charge air into the engine compartment. Its primary purpose is to alleviate excessive pressure in the intake tract by venting the compressed air produced by the turbocharger. This action ensures that the turbo remains operational without any abrupt pressure transition when you accelerate again.

It's important to note that the distinctive hissing noise is specific to open Blow Off Valves. Closed systems redirect the air back into the intake tract before the turbocharger, omitting the characteristic sound. In racing scenarios, turbocharged engines may not always feature a Pop Off Valve.

The Function of a Blow Off Valve

In essence, a Blow Off Valve, or Pop Off Valve, is designed to safeguard the turbocharger from potential damage caused by excessive pressure. These valves are exclusively installed in turbocharged engines to release excess pressure from the intake tract.

To better understand their function, let's take a look at how a turbocharger operates. When you accelerate, the turbocharger is driven by the exhaust gases from your engine, compressing these gases with the help of the compressor wheel. Even when you release the throttle, the turbocharger continues to supply compressed air. However, the closed throttle prevents this compressed air from escaping, leading to a buildup of pressure.

Enthusiasts who enjoy increased boost pressure levels would subject their engines to significant wear and potential damage without a Blow Off Valve. This is because the trapped air, unable to exit through the closed throttle, returns to the turbocharger, decelerating the compressor impeller and causing the turbo to lose momentum.

Here's where the Blow Off Valve comes into play. It opens when you release the throttle, allowing the excess air to divert away from the turbocharger before it can slow down the compressor impeller. This release of pressure also generates the distinctive hissing sound, ensuring the turbocharger can spin freely while protecting it from excessive wear.

Choosing Between Open and Closed Systems

The decision to install an open or closed system largely depends on personal preference. Closed systems, which redirect air back before the turbocharger, produce less noticeable "whoosh" noise compared to open systems. Closed systems maintain stable idling and offer responsive engine performance. For those who favor the open system primarily for the sound, it provides audible feedback with every gear change and coasting. An ideal solution for flexibility is to use a Blow-Off Splitter, allowing adjustment from fully closed to partially open.

Upgrading Your Blow Off Valve

To prevent power loss and potential damage due to increased charge pressure, it is advisable to upgrade your Pop Off Valve. Stock valves may not withstand the elevated pressure levels, leading to turbo and engine component damage. Popular choices for upgrading Blow Off Valves include engines and models that are typically favored by tuning enthusiasts:

1. 8T
2. Golf 5 GTI
3. Audi S3
4. Golf 6 GTI
5. Ford Focus
6. Opel Astra
7. Audi TT

Benefits of Upgrading

Upgrading your Pop Off Valve immediately rectifies power loss caused by backflowing air and excess pressure. It maintains consistent charge pressure, eliminating turbo lag and enhancing torque and power delivery. Upgraded valves are typically constructed from higher-quality materials, offering optimal turbo protection, improved performance, and a sporty sound.

Retrofitted Pop Off Valves:

Retrofit thrust diverter valves are engineered to maintain charge pressure consistently, in contrast to stock parts. In these upgrades, the valve piston is sealed by charge pressure, not a spring. This means that pressure enters the valve, compresses the piston, and is sealed by a rubber ring. This design ensures airtight sealing, with air escaping only when load conditions change, raising the piston and releasing pressure from the system.

Considerations and Installation

Open Blow Off Valve systems can result in rough idling, so it is advisable to use a splitter for added flexibility. Spring stiffness within the Blow Off Valve can be adjusted to match charge pressure levels, with harder springs suitable for higher pressure settings. Some valves are designed for "pull mode," working slower for extremely high charge pressures.

Installation is straightforward for those with some mechanical skill. However, if you lack confidence, professional installation is recommended. The process involves placing the valve between the throttle valve and the turbocharger, ensuring proper lubrication and connection to the vacuum system.

Approval and Road Use

Closed Blow Off Valve systems that redirect excess charge pressure back into the system are generally road-legal. In contrast, open systems that release air into the atmosphere, creating the distinctive sound, are not permitted for road use and are primarily reserved for motorsports.

Conclusion

The Blow Off Valve serves a crucial role beyond its iconic turbo-like sound. If you're passionate about tuning and operate at high boost pressures, upgrading your Pop Off Valve is a wise choice. Before installation, consider whether you prefer an open or closed system. Should you require assistance or advice, our customer support is available, and frequently asked questions can be found in our FAQ section.