What Is a Turbo Wastegate? (Full Guide)
Updated: Feb 1
✔ This article has been fact checked.
A wastegate is an exhaust bypass valve that is used to regulate the flow of exhaust gases in a turbocharged engine. It is an important component that helps to control boost pressure and prevent the turbo from over-speeding.
Boost pressure is the amount of extra air that is forced into the engine by the turbo, and it is an important factor in determining engine performance.
The wastegate consists of a valve that is actuated by a diaphragm or a spring. When the boost pressure reaches a certain level, the wastegate opens and allows some of the exhaust gases to bypass the turbine, reducing the amount of boost pressure being generated.
This helps to prevent the turbo from over-speeding and damaging itself.
In this article, we will delve into the details of what a wastegate is, the various types, whether you need one on a turbocharged engine, where it is located, and more.
Table of Contents:
Do You Need a Wastegate on a Turbo?
Yes, you need a wastegate on a turbocharged engine. The wastegate is an important component that helps to regulate boost pressure and prevent the turbo from over-speeding.
Without a wastegate, the turbo could potentially over-speed and suffer damage, which could lead to costly repairs or even engine failure.
Where Is the Wastegate on a Turbo?
The wastegate is usually located on the exhaust side of the turbocharger. It is typically mounted to the exhaust manifold or the downpipe, and it is connected to the turbo via a pipe or hose.
The location of the wastegate can vary depending on the specific design of the turbo and the engine, but it is typically found in close proximity to the turbo.
Types of Turbo Wastegates
Turbo wastegates are valves that are used to control the amount of boost produced by the turbocharger in an internal combustion engine.
There are two main types of turbo wastegates.
An internal wastegate is built into the turbocharger and is commonly found in smaller, less powerful engines, while an external wastegate is separate from the turbocharger and typically used in larger, more powerful engines.
Both types have their own advantages and disadvantages, and the appropriate type will depend on the specific needs and requirements of the vehicle and its engine.
> Read more about how a wastegate works
Internal Wastegate
Internal wastegates are built into the turbocharger itself and are commonly found in smaller, less powerful engines. They are typically easier to install and require less maintenance than external wastegates.
However, they may not offer as much precision and control as external wastegates, and may not be able to handle the increased boost levels needed for high-performance applications.
External Wastegate
External wastegates, on the other hand, are separate from the turbocharger and are usually found in larger, more powerful engines. They offer more precise control of boost levels and are better able to handle the increased boost levels needed for high-performance applications.
However, they are typically more complex to install and require more maintenance than internal wastegates.
Screamer Pipe (Atmospheric/Divorced Wastegates)
A screamer pipe, also known as a wastegate dump pipe, is a type of exhaust configuration that is often used on automotive turbocharged petrol engines with external wastegate setups.
The primary function of an exhaust system is to direct the engine's exhaust gases away from the vehicle and release them into the atmosphere.
However, these gases may contain harmful substances such as unburnt fuel or emissions that need to be treated before they can be safely released into the environment. This is typically done using a catalytic converter or muffler.
A screamer pipe bypasses this process by venting the exhaust gases directly to the atmosphere through a separate, un-muffled pipe. This type of exhaust configuration is known for its distinctive, loud noise, which is why it is often referred to as a "screamer pipe".
While some drivers may enjoy the unique sound of this exhaust setup, it is illegal for street use in many countries due to noise and exhaust emission regulations.
These regulations are in place to protect the environment and public health by limiting the release of harmful substances into the atmosphere.
How Is a Wastegate Controlled
There are several different ways that a wastegate actuator can be controlled, including the following.
Most modern cars use a pneumatically controlled wastegate control system.
Manually Controlled
Manually controlled wastegates are the most basic type of wastegate control. These wastegates are controlled by a lever or knob that is manually adjusted by the driver or mechanic. This type of wastegate is often used in older or simpler systems where precise control is not necessary.
Pneumatically Controlled
One of the simplest ways to control a wastegate is to use pneumatic closed-loop wastegate control system, which involves connecting the boost pressure directly from the charge air side to the wastegate actuator.
This can be done using a small hose that connects the turbocharger compressor outlet, charge pipes, or intake manifold to the wastegate actuator.
As the boost pressure increases, it pushes against the spring in the wastegate actuator, causing the wastegate to open further until equilibrium is reached.
An electronic boost controller can be used to provide more advanced control of the wastegate. Standard wastegates have one port for attaching the boost control line, but newer models may have a dual port design that allows for more complex control.
The dual port wastegate has an additional port on the opposite side of the actuator, which can be used to apply pressure in the opposite direction of the first port, helping the wastegate remain closed as boost pressure builds.
However, this requires more control ports on the solenoid or a separate boost control system with its own solenoid. Additionally, the second port can be controlled manually or with the use of CO2, which allows for finer control of boost levels.
It is worth noting that the second port is not necessary for all applications and may not be used in all cases.
Electronically Controlled
Electrically operated wastegates were used in some 1940s aircraft engines. These systems, which were made by General Electric, allowed pilots to select different boost levels using a cockpit control.
However, electric wastegates fell out of favor due to design philosophies that separated engine controls from the electrical system.
In recent years, electronic servo wastegate actuators have made a comeback in some modern vehicles.
For example, the Hyundai Sonata's 2.0-liter Theta II turbocharged gasoline direct-injection (GDI) engine, introduced in the 2011 model year, uses a PCM-operated electronic servo wastegate actuator.
This allows the vehicle to use a boost control strategy that reduces exhaust backpressure and improves fuel economy by opening the wastegate when boost is not needed. The wastegate is also held open during cold starting to lower emissions by speeding up the initial catalyst light-off.
Similarly, starting in November 2015, Honda's Earth Dreams direct injected turbocharged engines with 1.5-liter displacement began using an ECU-controlled electronic wastegate.
Hydraulically Controlled
In modern turbocharged aircraft, it is common to use a hydraulically controlled wastegate system that uses engine oil as the fluid. Inside the wastegate actuator, a spring pushes open the wastegate, while oil pressure works to close it.
The density controller, an air-controlled oil valve located on the oil output side of the wastegate actuator, regulates the speed at which oil bleeds back to the engine from the wastegate actuator.
As the aircraft ascends and the air density decreases, the density controller gradually closes the valve and traps more oil in the wastegate actuator, causing the wastegate to close and increase the speed of the turbocharger to maintain rated power.
Some systems also employ a differential pressure controller that senses the air pressures on either side of the throttle plate and adjusts the wastegate to maintain a set differential.
This helps to maintain an optimal balance between a low turbocharger workload and quick spool-up time, as well as preventing surging.
Wastegate Sizing
The size of a wastegate is directly related to the desired level of boost and the size and power of the engine.
A larger wastegate is generally needed for a big turbo and low boost, or a small turbo and low boost.
A smaller wastegate is typically used for a big turbo and high boost, or a small turbo and high boost.
However, exhaust flow and power also play a role in determining the appropriate wastegate size.
For example, a small wastegate may be sufficient for a big turbo and small engine with small power, but a bigger wastegate may be needed for a big turbo and big engine with small power.
On the other hand, a small turbo paired with a big engine at any power level will likely require a larger wastegate to prevent the turbine from overspinning due to excess exhaust gas volume.
The size of a wastegate has multiple factors, including the following.
Desired level of boost: A larger wastegate is typically needed for low boost, while a smaller wastegate is typically used for high boost.
Size of the turbo: A bigger wastegate is generally needed for a big turbo, while a smaller wastegate is typically used for a small turbo.
Power of the engine: Exhaust flow and power can also affect the appropriate wastegate size.
Size of the engine: A small wastegate may be sufficient for a big turbo and small engine with small power, but a bigger wastegate may be needed for a big turbo and big engine with small power.
What Happens if a Wastegate Fails?
If a wastegate fails, it can have serious consequences for the performance and safety of the vehicle. A wastegate is an exhaust gas bypass valve that is used to control the amount of boost produced by the turbocharger in an internal combustion engine.
It is designed to open at a predetermined pressure to release excess exhaust gases into the exhaust system bypassing the turbine of the turbocharger, this controls the boost pressure and prevents the turbo from producing too much boost.
If the wastegate fails to open when it is supposed to, it can cause the turbo to produce too much boost. This can lead to a number of problems, including the following.
Overboosting: If the turbo produces too much boost, it can cause the engine to overboost. This can lead to a number of issues, including engine damage, increased wear and tear on engine components, and reduced fuel efficiency.
Detonation: Overboosting can also cause pre-ignition or detonation, which is when the fuel in the engine ignites prematurely. This can lead to knocking or pinging noises, and can cause serious damage to the engine.
Increased stress on engine components: Too much boost pressure can also put extra strain on engine components, such as the pistons, rods, and crankshaft. This can lead to increased wear and tear and potentially result in engine failure.
If a wastegate fails, it is important to have it repaired or replaced as soon as possible to prevent these problems from occurring. A vehicle with a wastegate failure may enter a failsafe mode known as limp mode.
Where Is the Wastegate Hose?
The wastegate hose, also known as the actuator hose, is a small hose that connects the wastegate to the actuator. The actuator is a device that is used to control the movement of the wastegate valve, and it is typically located on the exhaust side of the turbocharger.
The wastegate hose is typically located between the wastegate and the actuator, and it is used to transmit the force from the actuator to the wastegate valve.
The location of the wastegate hose can vary depending on the specific design of the turbo and the engine, but it is typically found in close proximity to the wastegate and the actuator.
Where Is the Wastegate Solenoid Located?
The wastegate solenoid, also known as the boost control solenoid, is a device that is used to control the flow of exhaust gases through the wastegate. It is typically located on the exhaust side of the turbocharger, and it is connected to the wastegate valve via a small hose or wire.
The wastegate solenoid is typically mounted to the exhaust manifold or the downpipe, and it is connected to the engine control unit (ECU) via a wiring harness.
The location of the wastegate solenoid can vary depending on the specific design of the turbo and the engine, but it is typically found in close proximity to the wastegate and the actuator.
Sources
Wikipedia. "Wastegate" https://en.wikipedia.org/wiki/Wastegate
(Oct 18, 2022) https://www.turbosmart.com/news/the-ultimate-guide-to-external-wastegates/
Gareth Hanson. (Dec 2, 2014) https://aet-turbos.co.uk/turbo-tech-101-what-is-a-turbo-wastegate-and-how-does-it-work/