If you are a car enthusiast, especially a turbo fan, you have surely asked yourself this question at some point. A complicated question calls for a complicated answer. Let’s take it in order. What exactly are blow-off valves and why are they used?
Blow-off valves (BOVs) are an essential component in turbocharged systems. Their main job is to prevent damage to the turbocharger. In this article we look at how blow-off valves work, why they matter and how the right upgrade can improve the way your car runs.
How blow-off valves work
Every time you lift off the throttle in a turbocharged car, pressure builds up between the turbo and the throttle body. With the throttle closed, the only way out for that air is back through the centre of the turbo. Blow-off valves sit between the turbocharger and the throttle body, and their job is to release the excess air that builds up when the driver suddenly lifts off.
If the excess air is not released it can slow the turbo down and potentially damage it through sudden pressure changes, a phenomenon known as turbo flutter.
There are two types of blow-off valve: those that recirculate the air back into the system and those that vent the excess air to the atmosphere.
Car manufacturers usually opt for using blow-off valves that recirculate the air back into the system. One reason is that this arrangement is quiet, which is what most manufacturers want. They are also suitable for use on cars with a MAF sensor.
Valves that vent excess air to the atmosphere, on the other hand, are far louder. They are suitable for use on cars that need to vent a lot of air. Enthusiasts love them precisely because of the noise they make. Such valves are usually not suitable for cars set up for operation on the MAF sensor readings.
You also need to be careful because with an incorrectly fitted oil cooler the oil cannot reach its optimal operating temperature. We prevent this by fitting an oil thermostat.
Why do blow-off valves matter?
Turbo protection: They prevent damage to the turbocharger.
Sound: They make the distinctive whooshing sound enthusiasts love.
How to choose the right blow-off valve?
It is important to know that not every turbocharged car benefits from a blow-off valve. You will have to look this up yourself, either in the manual or online.
On cars with a MAF sensor you must choose a recirculating blow-off valve, because the MAF sensor measures the air entering the intake system. If the blow-off valve is fitted incorrectly, the MAF sensor will read the wrong values, which will cause running problems.
Blow-off valves come in various sizes, usually from 38 to 60 mm. In most cases you will not need to go above 50 mm, unless you have a wild car making serious horsepower.
Conclusion
Blow-off valves are essential for keeping turbochargers healthy and performing. If you need help choosing the right blow-off valve, you can contact us. We will gladly help you based on your needs.
P. S.
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