Blow Off Valves On Non-turbos & Automatic: Does It Work?

You may put a blow off valve on a non-turbo or automatic but it would not make the same sound as when you put it on a turbo.

For me, it’s the “Woosh” or “Bwaaaah sutututu” sound that comes from a turbocharged car that really gets me. It’s exhilarating. This is produced by a blow-off valve.

Let’s find out how a blow off valve works on non-turbos and automatic.

What is a Blow-Off Valve

Blow-off valves are an important component of a forced induction system because they relieve pressure spikes between the throttle body and the turbo.

A blow-off valve is connected to the intake tract. Inside the valve’s main housing is a vacuum chamber with a spring, a diaphragm and a valve. The diaphragm reacts to pressure changes. At a predetermined vacuum, it’s pulled toward the vacuum source, compressing the spring inside the housing. The spring is connected to a valve that pulls away from its seat and releases the unwanted boost pressure.

The pressure side of the valve is usually connected to the pipe between the turbo and the throttle, and a vacuum hose on the top of the valve is connected to the inlet manifold following the throttle body. The valve is held shut by a spring

Blow off valves are of 2 types;  recirculated or vented. The bypass valve recirculates the boost pressure back into the intake. While the vented Blow-off valve discharges the boost pressure into the atmosphere instead of back into the intake.

Some higher-quality blow-off valves allow you to select how much air is vented to the atmosphere and how much is reinjected into the turbo.

When it comes to BOV design, I prefer a diaphragm-style BOV because you can be sure the BOV chamber will seal, although the cheaper range of BOVs would still work, but you’re relying on a seal that’s dependent on the tolerance between the body of the BOV and the piston, which is fine when the unit is brand new, but tolerance levels will increase over time.

The primary goal of a blow-off valve (BOV) is to protect the turbo from damage while guaranteeing smooth and dependable operation.

How does  blow off valve work

Blow-off valves are used to avoid compressor surges, which can occur when the throttle on a turbocharged engine is suddenly closed.

When accelerating, your engine’s exhaust gasses, or more particularly, your turbocharger’s exhaust turbine, drive the turbocharger. The exhaust gasses are compressed by the compressor wheel on the other side. When you let go of the throttle, the throttle valve closes. Still, the turbocharger continues running and continues to produce compressed air. However, because the throttle is closed, this air has nowhere to go, and pressure develops.

When the throttle is closed, a vacuum forms in the manifold.

When the system is pressured, air returns to the turbo when the blow-off valve kicks in. It expels the compressed air into the atmosphere, saving the turbo from being damaged. This operation generates a range of noises that car lovers like. Surprisingly, some valves are designed to improve the sound. Some, for example, have trumpet-shaped outputs to improve the sound.

It expels turbocharged air that has come down the incorrect side of the intake manifold into the environment. Longer turbocharger life, faster spool, and improved transient responsiveness are all benefits of installing a blow-off valve.

Most aftermarket blow-off valves are tightly sprung and/or adjustable, so they do not leak when idle. If the valve is overly stiff, this can result in a compressor surge.

However, when it comes to performance, the BOV falls short. It’s only for show. Moreover, depending on the valve, tightening it so that it does not leak air at idle (which might cause rough idling or stalling) may trigger “compressor surge,” which is a fluttering noise produced when the turbo blade stalls out against high-pressure intake air.

How to Install a Blow off Valve

Depending on your vehicle, installing a blow-off valve might be a very simple process. Still, by doing so, you can improve your engine’s efficiency while also extending its life. Before installing a blow-off valve, always disconnect and remove the battery.

Blow-off valves are frequently referred to by their diameter, with 40mm being a popular size. The optimal valve depends on how much boost you’ll be running and the amount of physical space available for installation

Blow-off Valves on non-turbos & Automatic

You can install BOV on non-turbos or automatic just for the beauty of it but it won’t work the way it works on turbos. So, if you want that wonderful sound that turbocharged vehicles make when shifting gears, you’ll need a turbocharged vehicle.

 Some BOVs have a trumpet-shaped exit vent to allow the high-pressure air to create a louder sound as it exits the engine. It can make a gratifying whoosh or hissing sound while driving, which can turn heads.

A blow-off valve cannot be installed in a naturally aspirated vehicle because induction (the sucking of air into the engine) is accomplished through a vacuum. 

It’s possible to mount it, but there’s no pressure to blow off. The effect of installing this on a standard turbo will be minor at best.

Check out this adjustable turbo blow off valve from Amazon, it does its job and does not set off any check engine lights. It has an adjustable top on it for different types of boost pressures. It’s minor, but you can still tell the difference.

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Blow off valve without a turbo

Blow-Off Valves and turbochargers are commonly used together, so a blow off valve without a turbo is just paperweight.

Installing a Blow-Off Valve is typically the next step after installing a turbocharger. It helps the entire turbo system function more efficiently and makes the drive much smoother.

A turbocharger is a device fitted to a vehicle’s engine designed to improve the overall efficiency and increase performance.

A turbo consists of two sections connected by a shaft. On one side, hot exhaust gasses spin a turbine linked to another turbine, which sucks in and compresses air into the engine. With this , more air can enter the combustion chamber, more fuel can be added for more power, which gives the engine greater power and efficiency.

Turbochargers are sometimes referred to as “free power” devices because, unlike superchargers, they do not require the engine’s power to operate. A turbocharger is powered by the hot and expanding gasses that exit the engine; therefore, there is no drain on the engine’s net power.

Most new turbocharged cars come standard with a blow-off valve. However, it recirculates the vented air, so it lacks the characteristic sound of a vent-to-atmosphere blow-off valve. Recirculating BOVs are also known as bypass valves (BPVs).

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Can you use a blow-off valve without a turbo?

A blow off valve cannot be installed on a naturally aspirated vehicle since induction is accomplished by vacuum. Instead of the turbine pushing compressed air in, the engine sucks air in. When the throttle is closed, no air is drawn in, and no boost is bouncing back into a non-existent turbocharger turbine.

This then provides an answer to the question. NO! A turbo is required to install a blow-off valve! Else, you’ll have an expensive showpiece.

A blowout valve is normally only required in turbocharged systems since its role is to relieve pressure in a turbocharged vehicle’s intake system when the throttle is raised or closed. This style of valve would be useless if your automobile did not have a turbocharger.

Can you put a blow off valve on an automatic?

A blow out valve can be used on an automatic. Still, it isn’t necessary because the way an automatic shift works is nothing like that of a stick.

The transition to the next gear in an automatic is quite subtle, and you don’t have to let off the gas to shift. Although a BOV could be used on an auto motor, it is rarely necessary, and there is no need for a blow off valve on a N/A motor under any circumstances.

Can you put a blow off valve on an automatic turbo?

Yes, you can put a blow off valve on an automatic turbo, but it decreases performance as the stock By-Pass Valve is one of the most efficient designs.

You have to understand that not all turbocharged vehicles will benefit from a blow off valve; for vehicles that use mass airflow sensors (MAF), you must choose a blow off valve that allows for recirculation as the MAF counts airflow after it enters the intake.

A typical BOV installation will result in inaccurate MAF measurements, generating additional issues.

A recirculating blow off valve is a necessary part of cars with a turbocharger. The blow-off valve relieves the pressure created in the air intake system when the driver lets off the gas, and the throttle closes. 

The excess pressure builds up and is forced back into the turbo, causing the compressor wheel to slow and even stop the blades from turning. This results in a compression surge causing a turbo lag and thus a drop in performance. 

A recirculating blow off valve releases the pressure from the turbo, diverting the excess back into the engine, preventing the turbo lag caused by the excess pressure, and maintaining the turbo’s proper and efficient spool up.

Can you hear the blow off valve on the automatic?

A BOV is not as audible in automatic cars compared to when on turbos, so you may not hear it. In an automatic, the only time you’ll hear a BOV is if you give the car gas (pedal to the floor) and then quickly release the gas pedal. Then you could hear something

The first thing that comes to mind when you think of a BOV is a loud whooshing sound that will set any automobile enthusiast’s heart pounding. They do sound rather spectacular.

The entire purpose of the BOV device is to eliminate excessive pressure when you abruptly release and close the throttle. You don’t hear it as often since it is not the same in an automatic.

Not all BOVs are noisy, but for individuals looking for a silent turbo for aesthetic reasons or owing to state noise requirements, a recirculating BOV is the best option.

Benefits of the Blow-Off Valve

You can sound incredibly cool and act like you’re in a Fast and Furious movie.

Because the turbo produces excess gasses, the blow-off valve’s purpose is to remove these from the system so that the turbo can operate at peak efficiency.

Turbocharged vehicles without a blow off valve are susceptible to compressor surge, which can lead to performance and reliability difficulties. This could be costly.

You won’t have to worry with a reliable blow off valve setup because these unwanted gasses will be fired out of your BOV, delivering you an addicting and pleasing sound in the process.

5 Benefits of blow off valves

  1. Enhances throttle response.
  2. Increases the speed of the turboshaft.
  3. Surge load is removed from the turbo compressor wheel.
  4. Extra surge pressures are removed from clamps, silicone, and connectors.
  5. Restore the performance of your turbo system that was lost due to the lack of a blow off valve.

Aside from increasing the longevity and reliability of your setup, it can also help sustain turbine speeds in-between shifts, providing a performance boost to the vehicle. There aren’t many engine upgrades that can provide you with both dependability and power, so a BOV should be on your list if you’re using a turbocharger.

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Choosing a Blow Off Valve

Suppose you decide to install Blow off valve. In that case, either an open or closed system is a personal preference, among other factors. The traditional “whoosh” noise is less noticeable in closed systems, where the air is returned before the turbocharger, than in open systems. The closed system has the advantage of keeping the idle stable, and the engine response is correspondingly good. Should you choose the open system primarily because of the noise you have the benefit of being able to hear it with every gear change and coasting. The air simply exits easily into the engine area, and there is a “Whoosh” sound.

Personally, aftermarket BOVs are a wonderful improvement for anyone who doesn’t want to worry about boost leaks or a potentially failing turbo. If you ask me, apart from the various advantages of a BOV, I’d get one simply for the incredibly addicting “whoosh” sound!

Chai WJ.

Chai WJ.

I am a car enthusiast and a passionate rider who loves to discover new places. Since the pandemic, I can't go to places and I started to blog and share information that I learned. I'm not easily distracted, I just... OMG, do I hear a Supra?

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