A turbocharged engine is a complex system containing multiple components, each with a unique role. One crucial turbocharging part is the turbo wastegate. But what is a turbo wastegate, and what is its role?
To help you understand the basic working principles, applications, and types of turbo wastegates, we prepared an expert guide. Continue reading to enrich your knowledge about turbo wastegates.
Source: shutterstock.com / Photo Contributor: Kastaprav
What Is a Turbo Wastegate and What Does It Do?
A turbo wastegate is a bypass valve in a turbocharged engine system. Its role is to control the flow of the exhaust gases and divert a certain portion away from the turbine, controlling the speed of the turbine as well as controlling it doesn’t spin so fast.
So, what does a turbo wastegate do? The turbo wastegate limits the turbine speed, contributing to optimal boost pressure by the turbocharger. As the wastegate regulates the maximum boost pressure, it protects the turbocharger and engine from damage.
How does a turbo wastegate work?
Turbo wastegates have a valve that is controlled by a pressure actuator, which is linked to the turbo’s boost pressure. Depending on the wastegate, the actuator can be electronically or mechanically controlled.
Until the boost pressure exceeds the previously set maximum, a spring located on the inside of the actuator holds the wastegate closed. When the boost pressure reaches a pre-determined limit, the spring is compressed and opens the wastegate.
As the turbo wastegate is opened, the engine’s exhaust gases are released into it. The exhaust gases pass through the wastegate and bypass the turbine, and the turbine's speed is regulated. The wastegate’s role is crucial in the turbocharged system, as it matches the turbine’s rotating speed to the needs of the engine.
Types of turbo wastegates
Wondering where is the wastegate on a turbo? Well, when you are looking for new and used turbos for sale, you will notice that there are two types of turbo wastegates: external and internal.
External turbo wastegates are individual mechanisms with self-contained valves. They are typically located on the gas side of the turbocharger system and should be installed as close as possible to the turbine housing. If such placement is not possible, external turbo wastegates can be installed at the exhaust collector. Whichever the location, it is crucial for the turbo wastegate to have a good flow.
Internal turbo wastegates, as the name itself suggests, are built into the turbine housing. The built-in valve allows the excess exhaust pressure to route the exhaust pressure into the downstream exhaust. Typically, OEM turbocharged vehicles have internal turbo wastegates.
Both internal and external wastegates are controlled by a pressure signal from the intake manifold.
External turbo wastegates
External turbo wastegates are designed to be added to the manifold’s or header’s exhaust plumbing. In our experience, many choose external wastegates because they tend to improve the performance of the turbine and there is an option to vent the exhaust flow directly to the atmosphere. The most common applications of external wastegates are on high performance and race vehicles.
External turbo wastegates offer various advantages, such as large valve sizes, more advanced boost control, variety of spring options, and are easily serviceable. The biggest disadvantage of external turbo wastegates is that they are more expensive to install. The increased cost is because the exhaust manifold must be manufactured or, in some cases, modified.
Internal turbo wastegates
As the name suggests, the internal turbo wastegate is in the turbine housing itself. Internal turbo wastegates use a pressure box to open the flap inside and outside. The exhaust gases are released through the flapper and vents when the maximum boost pressure is reached.
- Internal turbo wastegates have valves with smaller diameters than their external counterparts. Because of their limited flow capacity, internal wastegates tend to produce lower boosts. Internal turbo wastegates are specifically designed for handling turbochargers at stock boost levels.
Source: shutterstock.com / Photo Contributor: Kastaprav
Quick Sizing Guide for Turbo Wastegates
Turbo wastegates come in various sizes, typically ranging from 38mm to 60mm and above. To choose the most suitable size, you should first determine the level of boost you want to achieve.
If your goal with the modification is to get a low boost, you should go with a bigger wastegate. On the contrary, high boosts are achieved with smaller wastegates.
Before you look for a turbo wastegate in our inventory, we recommend you check some of the sizing recommendations.
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Turbo size |
Engine size |
Power |
Recommended wastegate size |
|
Big |
Small |
Small |
Small |
|
Big |
Small |
Big |
Big |
|
Big |
Big |
Small |
Medium |
|
Small |
Small |
Small |
Small |
|
Small |
Big |
Any |
Big |
Signs of Faulty Turbo Wastegate
If you currently own a vehicle with a turbo wastegate, you should look out for these three signs, as they might indicate the turbocharged system component is malfunctioning:
- Reduced boost production
- Check engine light is on
- Decreased fuel economy
Bear in mind that the above-mentioned signs are also common for other faulty turbocharged system components. Hence, if you suspect that your turbo wastegate is failing, you should consult with a professional so they can do proper testing.
