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Internal vs External Wastegate (The Differences Explained)

Updated: Jan 8

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 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.


example of an internal wastegate

Pros

  • 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

  • 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.