Wastegate 101

What does a Wastegate do?

A wastegate (WG) is a boost-controlling device that limits exhaust gases going through the turbocharger. The primary function of a wastegate is to regulate the maximum boost pressure in the turbocharger system. This protects both the engine and the turbocharger. This is done by diverting the exhaust gases away from the turbine wheel in the turbocharged engine system. The diversion of exhaust gasses regulates the turbine speed, which in turn regulates the rotating speed of the compressor. To put it simply – a wastegate prevents the boost pressure from climbing indefinitely and consequently blowing the engine.

A wastegate consists of an inlet and outlet port, a valve and a pressure actuator. From there they can be broken down into two major types; internal and external.

Internal Wastegates

An internal wastegate comes in the form of a built-in bypass valve that is developed and designed to handle stock boost levels. Therefore, a lot of OEM Turbochargers use internal wastegates.

Turbosmart Universal Internal Wastegate
Turbosmart Universal Internal Wastegate

So, let’s go into how they work. In its resting position the valve is closed. This allows for full exhaust flow through the turbine. When pressure exceeds a specific limit, the force that is created opens the valve that routes some gases to the catalytic converter through a hollow passage in the turbo’s housing. When the pressure reduces back to a safe level the valve closes and the process will repeat.

BD Diesel Wastegate
BD Diesel Wastegate

The advantages of an internal wastegate include their simpler, and more compact installation. There is no need for external wastegate piping. The disadvantage in comparison to an external WG would be the limited ability to bleed off exhaust pressure. Running high boost through a factory internal WG can overpower the actuator spring, limiting maximum boost level. All of this is due to their relatively small diameter of the internal bypass valve. As a result, they are less efficient under high boost conditions, and an external wastegate is recommended.

External Wastegates

RDP Store - Turbosmart Ultra-Gate38 Wastegate
Turbosmart Ultra-Gate38 WG

An external wastegate is a separate self-contained device. It is commonly used with high performance aftermarket turbochargers that do not have internal wastegates. These wastegates are commonly used for regulating boost levels more precisely in high power applications. They feature larger inlet and outlet ports as well as stronger actuator diaphragms and springs. As a result, this allows for better control of high boost pressure. Therefore, most tuners will recommend an external wastegate for any engine producing 400hp or more.

Turbosmart 14psi Comp-Gate40 40mm External Wastegate - Blue | (TS-0505-1009) - Modern Automotive Performance - 1
Turbosmart Gate-40 External Wastegate

An external wastegate requires a specially constructed turbo manifold with a dedicated runner going to the WG. Additionally, the external wastegate may be part of the exhaust housing itself. Furthermore, it is also possible to use an external wastegate with an internally gated turbocharger. One way this can be achieved through a specially designed bracket that easily bolts on and restricts the movement of the actuator arm, keeping it from opening. However, if you’re looking to use an external WG with an internally gated turbocharger we advise speaking to your mechanic before making any decisions.

External wastegates can be controlled and operated in several different ways.  Those ways include the use of a traditional actuator, an electric solenoid or electric actuator. The electric actuator is the most precise and advanced method of WG control since it involves the use of the PCM (powertrain control module) that adjusts the position of the wastegate valve.


There are several manufacturers who developed high-quality wastegates. Those manufacturers include:


BD Diesel


In the future we will feature articles covering each of their wastegates in more depth. So be sure to check back regularly!

In Conclusion

Depending on your vehicle’s specific needs, the type of wastegate you need will range. It’s always smart to include your tuner and mechanic in your decision. They can best help you achieve your goals for your vehicle. You can always head over to our website or give our shop a call as well. We have an extremely knowledgeable staff who can assist you in making a better decision.