Dump Valves On Diesel: Does It Work & Are They Legal?

By September 14, 2022Common Questions, Wastegate

The Dump valve is also the blow-off valve used on turbocharged engines. It is possible to use a dump valve on diesel, which will work perfectly, but it is much more complicated than you think.

Generally, the turbocharged diesel engine does not need a turbo dump valve; however, it would work fine with high-performing diesel engines.

Personally, I have installed a dump valve on my high turbocharged diesel engine. I did this to improve the sound of my engine, and I must say that I was not disappointed. The dump valves worked fine, and I did have to experience any problem with the installation.

What Are Dump Valves?

Dump valve works by releasing built up pressure created from turbo.

Dump Valves are instruments installed primarily on a turbocharged engine and used to reduce the pressure the turbocharger creates in the intake system. It does this by redirecting the pressure air into the intake.

When your vehicle is speeding up, air fills up the intake system coming from the turbo compressor. Once the throttle closes up, there is no means for the pressurized air to go into the engine.

This pressure built up to find a way to escape, and the only way to do so was by passing through the turbo compressor. When the pressurized air passes through the turbo compressor, it may create some noise that could be annoying. 

The pressure building up in the engine could also cause the turbo parts to wear within time, causing engine failure. Relating a failed turbo to a lack of dump valve is debatable, but pressurized air passing through the compressor must stop. One way to do so is to install a dump valve which could also be called a blow-off valve.

The Dump valve is a vacuum pressure valve that uses sensor signals, which tell the valve when to open or close. The valve will help the turbo engine relieve additional turbo pressure. It is often between the throttle, vacuum hose, and turbo, located at the top valve connected to the inlet manifold.

Do Dump Valves Work On Diesel Engines

A dump valve on your diesel engine is possible and will be complicated, but it is highly unnecessary. Dump valves function between the turbo and throttle; unfortunately, the diesel engine doesn’t use a throttle.  

Unlike the gasoline engine, there is no need for a dump valve with the diesel engine. In a gasoline car, when the engine is accelerated, pressure is generated and moves through the throttle body, which then finds its way into the intake manifold.

The diesel engine is throttled by fuel rather than air, unlike the gasoline engine. It does not create as much air pressure in the engine as the gasoline engine, which is why it does not need a dump valve.

When you press the acceleration with a diesel engine, you are simply giving a command to the fuel injector to pump in more fuel to increase the car’s speed. Since no throttle creates air pressure, there is no need for a dump valve to divert air pressure.

However, it is possible to install a dump valve on a diesel engine, but it is only necessary if installed on a high-performing engine that uses huge turbochargers.

The diesel engine uses custom-made Dump Valves, which have a unique design to help the turbocharger achieve the needed boost.

The dump valve can also help your turbocharged diesel engine achieve an improved sound. It is famous for giving your vehicle that “pshhhhh” sound when you hit acceleration. 

Also Read: Muffler Delete On Diesel: Does It Work? (Horsepower & Sound)

Are Dump Valves Legal?

In most states in the United States, Dump Valves could be illegal because they modify your emission system. Any modification that will affect the initial factory settings of your vehicle emission rate is unlawful.

Unfortunately, the dump valve may affect your vehicle’s original factory level of emission. The dumb valve may affect emission in many ways, such as contamination received by the dumb valve from the turbo seal. 

Also, people buy Dump valves mainly because of the sound modifications. It gives a loud and exotic sound to your engine, which many people like. However, when the sound from your car due to the dump valve modification becomes too loud, it becomes illegal. 

There are a lot of factors that will determine the legality of your dump or blow-off valve. Some factors that could affect the legality of your dump valves include sound, emission modification, and the location where you are driving. 

With all this said, the legality of the dump valve still depends on the state laws of where you stay. A state like California has a stricter law on car modification, while Oklahoma is more lenient on things like this.

Also Read: Blow Off Valve Vs Wastegate: Function, Horsepower & Sound


Q: Can a Dump Valve Damage an Engine?

Dump valves are completely safe to use with your turbo engine. It provides a great way to relieve pressure from the turbocharged engine system without causing any damage to the engine.

Dump valves work better with turbocharged engines because of the air pressure generated by the turbo. Installing the modification on a non-turbocharged engine is a waste of time. 


Q: How Do Dump Valves Work? 

A dump valve is a valve that makes use of pressure signals located in the manifold and inlet. These pressure signals help the dump valves stay close and tell the piston when to open and close.

When the engine is idle, a vacuum is at the top of the dump valve that constantly sucks open. The dump valve needs to be closed during idle; with the help of spring present in the valve, it helps keep the piston closed. 


Q: Does a dump valve improve performance? 

Installing a dump valve will improve many aspects of your engine’s performance. You can expect an improved boost level when hitting the throttle pedal. The engine will also respond faster to the throttle when compared with a turbo without a dump valve or one using a factory dump valve. 

Ifandi L.

Ifandi L.

Passionate about everything mechanical. Ifandi has been involved with motorcycles and cars since the old days - in his family's auto parts shop. Want to keep in touch? Scream "STRAIGHT PIPEEEEE" at the top of your lungs and Ifandi will show up.

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