Internal vs External Wastegate (The Differences Explained)

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The wastegate is a vital component in a turbocharged engine system. Its primary function is to act as an exhaust gas bypass valve and regulate the amount of exhaust gas flowing through the turbine, ensuring that it operates within its optimal range.

A wastegate valve can be either an internal wastegate with the valve integrated into the turbine housing and opened by a turbo-mounted actuator, or an external wastegate which is a separate valve and actuator unit not connected to the turbo.

In this article, we will explore the differences between internal and external wastegates, including their pros and cons, to help you decide which one is best for your specific needs.

Table of Contents:

• What a Wastegate Is

• Internal

• External

• Conclusion

What Is a Wastegate?

Before diving into the internal vs. external wastegate comparison, it's essential to understand what a wastegate is and how it works.

A wastegate is an exhaust gas bypass valve that is used to regulate the flow of exhaust gases in a turbocharged engine. It is connected to the exhaust manifold and the turbine housing of the turbocharger.

The wastegate valve is opened and closed based on the pressure of the exhaust gases, which is controlled by a boost controller.

When the boost pressure exceeds the predetermined level, the wastegate valve is opened, allowing a portion of the exhaust gases to bypass the turbine and reduce the boost pressure.

When the boost pressure falls below the predetermined level, the wastegate valve is closed, directing all of the exhaust gases through the turbine and increasing the boost pressure.

Internal Wastegate

An internal wastegate is a type of wastegate that is integrated into the turbine housing of the turbocharger. It is opened and closed by a boost-referenced actuator that is mounted on the turbo.

Pros

An internal wastegate has multiple advantages, including those below.

• Simplicity: An internal wastegate is relatively simple to install and maintain. Since it is integrated into the turbine housing, there are fewer parts and connections to worry about.

• Compactness: An internal wastegate takes up less space and is more compact compared to an external wastegate. This can be beneficial in applications where space is limited.

• Less expensive: Internal wastegates are less expensive than an external wastegate setup.

• Aftermarket upgrades: There are usually more aftermarket upgrades and parts for an internal wastegate.

Cons

There are also quite a few disadvantages of an internal wastegate, such as those below.

• Limited adjustability: An internal wastegate is not as adjustable as an external wastegate. The boost pressure and the opening of the valve are predetermined by the actuator, which can be challenging to modify.

• Limited control: An internal wastegate provides limited control over the boost pressure and the exhaust flow, which can impact the performance of the engine.

• Limited wastegate port and valve size: This issue can cause overboosting in high performance applications because the wastegate port and valve are too small to divert enough gas away from the turbine. This can lead to excessive boost pressure and potentially damage the engine.

• Linear response time: The wastegate valve in an internal wastegate will lift off the seat slightly earlier than its preset spring pressure due to positive pressure in the cannister pushing against the diaphragm/spring. While this happens relatively quickly, it may not provide the desired "aggressive" feeling in high performance applications. In OEM applications, this may not be an issue.

• Boost spiking in high performance applications: In high performance or load-demanding situations, the actuator may not open fast enough, allowing the turbocharger to produce more boost pressure than the actuator spring. Once the actuator catches up, boost pressure is returned to the preset spring pressure.

• Springs cannot be changed: Internal wastegate springs cannot typically be changed, with the exception of aftermarket actuators. This may limit the ability to modify the wastegate's spring pressure and boost pressure control.

Can You Adjust an Internal Wastegate?

An internal wastegate is a valve within the turbocharger of an internal combustion engine that is used to regulate the amount of exhaust gas that flows through the turbine. It is designed to prevent the turbocharger from overspeeding and potentially damaging the engine.

Adjusting the internal wastegate involves changing the position of the wastegate actuator, which is the mechanical component that controls the movement of the wastegate valve.

Adjusting the internal wastegate can have a significant impact on the performance of the engine, as it can affect the boost pressure and airflow to the engine.

To adjust an internal wastegate, you will need to follow the steps below.

1. Locate the wastegate actuator on the turbocharger. This is typically located on the compressor side of the turbo, near the outlet of the compressor housing.

2. Determine the desired boost pressure for your engine. This will depend on the make and model of your vehicle, as well as your intended use for the vehicle.

3. Measure the current boost pressure of the engine using a boost gauge.

4. Compare the current boost pressure to the desired boost pressure, and determine if an adjustment is necessary.

5. If an adjustment is necessary, use a wrench to loosen the lock nut on the wastegate actuator rod.

6. Turn the wastegate actuator rod clockwise to increase boost pressure, or counterclockwise to decrease boost pressure.

7. Re-tighten the lock nut to secure the wastegate actuator in place.

8. Recheck the boost pressure using the boost gauge to ensure that the desired boost pressure has been achieved.

It is important to note that adjusting the internal wastegate can have unintended consequences on the performance and reliability of the engine. This is especially true if it is a mode engine with an ECU controlled boost pressure.

It is recommended to consult with a mechanic or a professional tuner before attempting to adjust the wastegate on your own.

External Wastegate

An external wastegate is a standalone valve and actuator unit that is completely separate from the turbocharger. It is connected to the exhaust manifold and the turbine housing through a separate pipe.

Pros

There are many advantages to using an external wastegate, such as the following.

• Adjustability: An external wastegate offers more adjustability compared to an internal wastegate. The boost pressure and the opening of the valve can be modified using the actuator, which provides more control over the engine's performance.

• Better boost control: An external wastegate provides better control over the boost pressure and the exhaust flow, allowing for more precise tuning of the engine.

• Large valve sizes: External wastegates often have valves and ports that are larger, up to 60mm or more, allowing them to divert a greater amount of exhaust gas compared to internal wastegates. In contrast, internal wastegates usually have valves that are 20mm-25mm in size.

• Larger diaphragm and heavier spring tensions: These features allow an external wastegate to remain closed until the preset spring pressure is reached, providing a more "aggressive" feel and enabling the turbocharger to reach its preset boost pressure faster than an internal wastegate.

• Easily serviceable: External wastegates are generally easier to service and maintain compared to internal wastegates.

• Spring options: External wastegates offer a variety of spring options, allowing users to increase or decrease boost pressure as needed.

Cons

There are also a few disadvantages to this type of wastegate, including those listed below.

• Complexity: An external wastegate is more complex to install and maintain compared to an internal wastegate. It requires additional parts and connections, which can be challenging to manage.

• Larger size: An external wastegate is larger and takes up more space compared to an internal Wastegate, which may be an issue in applications where space is limited.

• More expensive: An external wastegate setup is more complex, requires more parts, and usually requires specialist tuning, this all increases the cost.

Is an External Wastegate Better Than an Internal Wastegate?

There is no straightforward answer to this question as it ultimately depends on your specific needs and preferences. Both internal and external wastegates have their own set of pros and cons, and it's essential to consider them carefully before making a decision.

If you need more adjustability and control over the boost pressure and exhaust flow, then an external wastegate may be a better choice for you. On the other hand, if you prioritise simplicity and compactness, then an internal wastegate may be more suitable.

Is an External Wastegate Necessary?

Whether or not an external wastegate is necessary depends on the specific requirements of your engine and the intended use of your vehicle.

Some of the factors that may influence the need for an external wastegate include the size and performance of the turbocharger, the power output of the engine, and the type of driving that the vehicle will be subjected to.

In some cases, an external wastegate may be necessary to ensure that the turbocharger is operating within its safe limits and to prevent damage to the engine.

For example, if you are using a larger turbocharger or you are planning to make significant modifications to your engine to increase power output, an external wastegate may be necessary to prevent the turbo from overspeeding.

On the other hand, if you are using a smaller turbocharger or you are not making significant modifications to your engine, an external wastegate may not be necessary.

In these cases, the internal wastegate within the turbocharger may be sufficient to regulate boost pressure and prevent the turbo from overspeeding.

Ultimately, whether or not an external wastegate is necessary will depend on your specific engine and driving needs. It is recommended to consult with a mechanic or a professional tuner to determine the best course of action for your vehicle.

What Is the Point of an External Wastegate?

The main purpose of an external wastegate is to allow the driver or tuner to precisely control the boost pressure of the engine.

By adjusting the position of the wastegate valve, the amount of exhaust gas that flows through the turbine can be regulated, which in turn affects the boost pressure and airflow to the engine.

In addition to controlling boost pressure, an external wastegate can also improve the overall performance of the engine by allowing it to operate more efficiently.

By limiting the amount of exhaust gas that flows through the turbine, an external wastegate can reduce the amount of heat and backpressure that the engine experiences, which can result in increased power output and improved fuel economy.

External wastegates are commonly used in high-performance vehicles and in engines that have been modified for increased power output. They can be particularly useful for drivers who are looking to fine-tune the performance of their engine and achieve specific boost pressure targets.

Conclusion

Internal and external wastegates are two different types of exhaust gas bypass systems that are used to regulate the flow of exhaust gases in a turbocharged engine. Each type has its own set of pros and cons, and it's essential to consider them carefully before making a decision.

If you need more adjustability and control, then an external wastegate may be a better choice for you. On the other hand, if you prioritise simplicity and compactness, then an internal wastegate may be more suitable.

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