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Wastegate: Function, Design & How It Works (Explained)

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Last Updated on: 7th September 2023, 12:36 am

Turbocharging is common in modern vehicles to boost power and efficiency. A wastegate is used to control the boost pressure generated by the turbo.

In this article, we’ll discuss the function and role of the wastegate, how it works, the different types, and more.

view inside a turbocharger and internal wastegate

Turbocharging and Boost Pressure

The turbocharger harnesses the exhaust gases to drive a turbine and in turn a compressor wheel, which pressurises air and forces it into the engine’s combustion chamber.

This increased air pressure allows engines to burn more fuel, producing higher power outputs than naturally aspirated counterparts.

Central to this process is the concept of boost pressure, which measures the density of air delivered to the engine, usually measured in psi or bar.

Understanding the Wastegate

The wastegate is the primary method of regulating the boost pressure provided by the turbocharger.

It is a valve mechanism designed to regulate the flow of exhaust gases through the turbocharger’s turbine, controlling the speed at which the turbine spins and thereby the boost pressure generated.

Its primary function is to keep the boost air pressure within a small range and to prevent over-boosting, a condition where excessive intake air pressure could lead to engine damage.

The primary function of the wastegate is to redirect surplus exhaust gases away from the turbine. This action effectively manages the turbine’s velocity, preventing it from reaching excessive speeds.

diagram showing the workings of a turbo and internal wastegate

How the Wastegate Works

A wastegate is a type of bypass valve. It is managed by a pressure actuator that connects to the turbo’s boost pressure.

  • Within the actuator, a spring with a predetermined stiffness keeps the wastegate closed.
  • If the boost pressure goes beyond the predetermined limit, the spring is compressed.
  • As a result, the wastegate gradually starts to open. This action permits the passage of exhaust gases, diverting them away from the turbine.
  • The outcome is the regulation of the turbine’s speed and air pressure generated by the turbocharger.
diagram showing the flow of gases through a turbocharger and wastegate
Diagram showing the flow of gases through a turbocharger and wastegate.


Wastegates come in two primary forms: internal and external.

Internal wastegates are integrated into the turbocharger housing, compact and efficient in design.

External wastegates are separate units that are not attached to the turbo, they’re often chosen for their enhanced control capabilities and other characteristics.

The choice between the two depends on factors such as engine design and the desired level of control over boost pressure, among others.

You can read more here about the differences between internal and external wastegates and the advantages of each type.

Divorced/Atmospheric Wastegates

Although not technically a type of wastegate on its own, it’s still a different type of setup.

In a “divorced” setup, the wastegate releases gases directly into the atmosphere rather than channeling them back into the engine’s exhaust.

This setup aims to prevent disruption to the exhaust flow and lower overall back pressure in the exhaust system.

A name used for this divorced wastegate setup is often called a “screamer pipe” due to the unfiltered and unmuffled release of exhaust gases, resulting in a very loud sound.


The wastegate’s role extends beyond preventing over-boosting.

By precisely managing boost pressure, the wastegate ensures that the engine operates within its optimal efficiency and power output ranges across varying RPMs and driving conditions.

This balance contributes to engine longevity, reliability, and a seamless driving experience.

Boost Control Strategies

Modern engines rely on engine control units (ECUs) to manage various aspects of performance and function, including wastegate and boost control.

Open-loop and closed-loop boost control strategies determine how the wastegate responds to changing conditions.

Open-loop control uses pre-programmed maps, while closed-loop control involves real-time feedback for more precise adjustments, ensuring consistent performance.

Tuning and Adjustments

Enthusiasts often seek to increase their engine’s performance by tinkering with the wastegate settings.

Aftermarket modifications, including wastegate upgrades and stiffer springs, can provide substantial power gains by allowing higher boost pressure levels.

However, it’s imperative to exercise caution and ensure proper tuning. Inaccurate adjustments can lead to engine damage or even catastrophic failures.

Can you run a turbo without a wastegate?

Yes, a turbo can technically run without a wastegate but the boost pressure would be unregulated. All modern turbocharged engines have some form of wastegate.

What happens if the wastegate fails?

If the wastegate fails the ECU will likely put the vehicle into a “limp mode” preventing the engine from reaching RPMs high enough to cause over-boost.

  • Andy Lewin

    Andy Lewin is a senior mechanic, ASE qualified master technician, and an experienced automotive engineer.He's passionate about serving the automotive community with the highest-quality and trustworthy information on all things automotive. He loves to write about car repairs, maintenance, car modifications and tuning, faults, and much more.

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