How Does a Wastegate Work? Everything You Need to Know About Wastegate Turbochargers

Need higher fuel economy and lower emissions?

Looking to enhance speed and power?

The turbocharger is just the thing for internal combustion engines. From diesel to gasoline, V-8s to hybrids, demand for turbochargers continues to be high. While turbo technology is associated with high-performance cars and racing the reality is very different.

A turbocharger adds to engine performance by recycling the energy in exhaust gases. This results in more energy delivered by a smaller engine.

Get to know your turbocharger components. Read on to learn “How does a wastegate work?”

Why Use a Turbocharger?

Engines make power by burning fuel to drive pistons in a cylinder. The burning fuel pushes the piston outstroke to shafts and gears. The in-stroke pushes the waste air and fuel mixture out of the cylinder as exhaust.

The amount of power an engine produces relates to how fast it burns fuel. More and bigger cylinders mean more fuel per second. This means more power to the wheels.

This is why fast sports cars might have 12 cylinders and little economy vehicles might have four cylinders. A turbocharger forces more air into the cylinders each second so they can burn fuel at a faster rate.  This means a little more energy from each stroke.

How does this increase fuel efficiency if you burn more fuel? More efficient fuel burning means fewer emissions and more power from a smaller, lighter engine. This makes a vehicle lighter and more efficient.  A turbocharged four-cylinder engine can replace a less efficient eight-cylinder engine. This gives better performance and reduces pollution and fuel consumption.

How Does a Turbocharger Work?

A turbocharger uses the energy from exhaust gases to drive a turbine. The turbine drives an air compressor to push extra air into the cylinders. This allows them to burn more fuel each second.

A turbocharger is two small impellers (air fans) on a metal shaft that spin together.  One of the impellers is the turbine.  It sits in the exhaust stream from the cylinders. A wastegate controls the flow of hot exhaust gas you can read more here.

As the cylinders force hot exhaust gases past the first impeller blade, it rotates. The shaft the impeller is attached to rotates as well. The second impeller fan (compressor) spins as well. It is inside the air intake and as it spins, it draws in air and forces it into the cylinders.

Air compression generates heat, so the excess heat is channeled away by a heat exchanger before the compressed air is forced into the cylinder.

What Does a Wastegate Do?

A wastegate protects your engine from excess pressure. It monitors the pressure of the entering compressed air into the cylinder and controls the volume of hot exhaust gases passing over the turbine.

It can be a simple mechanical valve or computer-controlled.

How Does a Wastegate Work?

At its most basic, a wastegate consists of a pneumatic actuator attached to the exhaust housing. A sensor line runs to the compressor housing to detect boost pressure.

As boost pressure rises, the pressure in the sensor line increases. At a certain point, the pressure is enough to open the spring-loaded valve to allow exhaust to bypass the turbine. This allows the turbine to slow and reduce the pressure.

Another popular control method for electronically controlled engines uses an electric solenoid to position the wastegate. Vacuum from the vacuum pump opens and closes the valve. An electronically controlled actuator adjusts constantly to maintain peak boost pressure and prevent manifold pressure oversupply or turbine overspeeding.

Wastegate control by means of an electric actuator is increasingly popular for turbocharged engines. Instead of manifold pressure or a vacuum source for control, these wastegates are controlled directly by the PCM. The PCM signals an electric solenoid to adjust the position of the wastegate valve.

For a visual demonstration of ” How does a wastegate work?”  Engineering Explained does an excellent job. A wastegate creates a controlled leak of exhaust from the turbine housing to slow the turbine.

Types of Wastegates

There are two main types of wastegates for turbochargers.

External Wastegates

High power engines for performance and race vehicles use specialized turbochargers and very high pressure. An external wastegate is a separate, self-contained mechanism fitted to the exhaust manifold or header.

External wastegates have large intakes and outlets, high tension springs and large actuator diaphragms to effectively control higher compressed gas pressures.

Most large frame turbochargers need external wastegate systems. Any engine producing more than 400hp can overpower a factory standard wastegate system.

Internal Wastegates

Most turbochargers are fitted with factory-standard internal wastegates. A valve is built into the turbine housing. The valve is controlled by a spring-loaded actuator and chamber. The chamber is tied to a pressure line in the compressor cover.

This valve is controlled by an actuator, which consists of a spring and a sealed chamber, and this chamber is linked to boost pressure (usually via a pressure source found on the compressor cover of the turbocharger).

Internal wastegates are meant for regular driving and standard pressure levels. They are insufficient for performance tuners and cannot protect an engine from damage under maximum speeds.

Looking for More Information Beyond Turbochargers?

Whether you are a performance tuning enthusiast looking to modify your engine or a minivan mom comparing fuel economy and engine performance, it’s important to do your research before buying. There are no “dumb” questions.

So go ahead and ask “How does a wastegate work?” or “How does a turbocharger help me?” With the answers in this article, you know enough to ask more questions!

Turbochargers use energy that would otherwise be wasted to force more air into the combustion chamber for efficient consumption. This produces more energy from the fuel and more power than a similar engine without turbocharging.

For more answers to car questions, keep reading this blog!

Author: Brandon Park