Do you know what blow off valve is? If you have no idea what this car mod is, then this blog post is for you!
You often see this mod in petrol engines where you hear that whappish sound coming from the turbo. But the question is, will this mod be as effective in diesel engines as well? Or better yet, is blow off valve necessary for diesel engines?
I will discuss these questions below and see if your car really needs this aftermarket modification.
What is a Blow Off Valve?
A blow-off valve (BOV) or also known as dump valve or compressor bypass valve, is a pressure release system that is often found in turbocharged engines. Its main function is to “dump” the excess load off the turbocharger when the throttle is shut closed.
To easily understand what BOV is, you first need to know how air intake system works.
Engine needs both fuel and air mixture to get successful compression of ignition, which helps the car run. Blow off valve is situated between the turbocharger and the throttle body, so its function is within the air intake system.
Air enters the air filter housing, then the amount of air that will enter the turbo is calculated by the mass airflow sensor. The air will enter the turbocharger then to the intercooler, then to the throttle body, and lastly into the inlets of intake manifold to the cylinders.
Now in gasoline engines, drive-by-wire throttle body is designed to keep the throttle or valve closed when the accelerator pedal is not depressed. This is to avoid too much air entering the combustion chamber.
But in this case, the turbocharger continuously draws air to the throttle body, which puts too much pressure to the charging hoses of the intercooler, sending shockwaves back through the turbo compressor which can potentially cause damage.
This is where blow-off valve comes in.
Blow-off valve helps release that trapped air into the atmosphere instead of recirculating it within the charging hose pipes. This blow-off action produces a “hissing” sound, which many car enthusiasts love.
Some aftermarket BOV’s are even fitted with sound amplifier to increase its auditory effect.
You can check out some of the best blow off valve in the market at Amazon.com.
Is Blow Off Valve Ideal for Diesel Engines?
Now you are probably wondering why diesel engine cars don’t have blow-off valves? Well, you can install an aftermarket BOV but it will completely do nothing for your engine. Why?
Because diesel engines don’t have a throttle plate! And even if they do, it is always 100% open all the time. This means that there’s no need for any pressure to be dumped to the atmosphere.
In short, diesel engines don’t need blow off valves. Unless if you have a high performance turbocharged diesel engine where a BOV can be beneficial.
So why people install blow off valves in ordinary trucks and SUV diesel vehicles? Well, it for aesthetic purposes only. Yes it can produce that hissing whapish sound, but it could even give more disadvantage that good for vehicle.
Conclusion
That’s how a blow off valve works and now you know that it can only be functional in petrol-based engines, not in diesel cars.
So the next time that an auto shop entices you to buy and install a blow off valve into your diesel engine, you already know that blow off valve is useless for your car.
Here is an in-depth explanation video regarding this topic. Take note that the video is in Tagalog but has English subtitle. Enjoy the video!
