How do turbocharger wastegates work

On the surface, it sounds like a simple premise, and in fact, a wastegate is a simple device. The problem comes from the pressure in the exhaust system, called turbine inlet pressure that can bear against the valve, overpowering the spring in the actuator, and forcing the wastegate open at lower than intended boost levels. Original equipment turbocharger wastegate actuators are selected or engineered for a specified boost level and turbine inlet pressure.

To keep costs down, such actuators are usually just big enough to do the job at the stock boost levels. If the turbocharger boost is increased for additional airflow and performance, the stock wastegate actuator is frequently incapable of holding the wastegate fully closed until the higher boost level is reached. With a turbo, it's hot exhaust gases that make your world go 'round. At a certain point, however, your boost pressure is sufficient and some of that hot air can bypass the exhaust turbine.

This is the point at which your wastegate actuator starts to respond. The wastegate opens up and the exhaust gases have a different path to freedom. You've opened up a bypass valve that sends this hot air in a different direction. Engineering Explained goes into a bit more detail with a lot more clarity than that.

Also, the video above briefly explains the difference between internal and external wastegates. Now that you possess this knowledge, go forth into the world and impress your automotive enthusiast friends the next time the topic of turbos spools up. Sign up to get the latest performance and luxury automotive news, delivered to your inbox daily! I agree to receive emails from Motor Authority.

I understand that I can unsubscribe at any time. In addition, the wastegate valve prevents the turbocharger from over-running. Particularly, it also avoids the engine from over-boost and prevents any mechanical failure. This feature in the turbocharger consists of a bypass valve. It circumvents some part of the exhaust gas going to the turbine and releases them into the outlet.

Furthermore, the waste-gate turbocharger has a bypass valve built into the turbine housing. It diverts some of the exhaust gases away from the turbine wheel through this valve.

The internal construction of the turbine consists of the wastegate valve and hollow passage within the turbocharger. So, it allows some of the boost pressure to enter into this passage. Then, the exhaust system automatically routes the bypassed exhaust gases to the catalytic converter and tailpipes.

In this system, the speed of the turbine wheel determines the diversion of the exhaust gases.