FAQ: Internal vs External Wastegates

FAQ: Internal vs External Wastegates


The question we often hear from customers about turbochargers or turbo kits in general is the age old debate of internal vs external wastegates. Which wastegate should I choose? Which wastegate is best? These are all questions in the Internal vs External Wastegates debate that vary on the usage and intended purpose of your vehicle.

If your vehicle came equipped with a turbocharger from the factory, chances are you have an internal wastegate. While the design is simple and easy to maintain, the shortcomings of the internal wastegate can become dangerous especially when turning up the boost.
Wastegates are designed to bleed positive exhaust gases away from the turbo, therefore controlling boost and allowing the tuner to dial in the proper ignition and fuel parameters. When factoring the Internal vs External Wastegates debate, there’s two ways they each operate.
Internal wastegates are built into the exhaust housing of the turbo directly, for overall cost efficiency and ease of install. External wastegates are plumbed into the exhaust manifold or 02 housing of the vehicle to bleed pressure away and control boost.
Aftermarket gauges are a must on any turbo vehicle.
In most instances however the OEM manufacturer has accounted for such measures and can usually size the internal wastegate flapper size accordingly. The problem occurs when enthusiasts bolt on a larger turbo, one that may be designed for “bolt-on” performance in theory but can also lead to disaster.
Aftermarket Actuators like this Forge unit can help control any boost issues you may have with a larger turbo.
Often times these large turbos can quickly overtake the original OEM internal wastegate design and flow resulting in overboost or boost spiking. Installing an aftermarket internal wastegate actuator is a great way to help settle some of the boost issues you might be having if you have bolted a bigger turbo onto your stock manifold.
Aftermarket wastegate actuators can be taken apart and set with different spring rates to give you more boost and control
If you are interested in more information on how to install an adjustable internal wastegate actuator, click here. For more on Internal vs External Wastegates, continue onward.
Q: Why should I need to go to an external wastegate?
A: It will provide true control over the boost your turbocharger is producing, unless emissions laws in your state dictate that you must reroute the external wastegate back into your exhaust. Check with your local authorities for further information or check our emissions law page.
A Mitsubishi Lancer Evolution VIII Big 16g exhaust housing
Internal wastegates can become troublesome when the valve opening cannot keep up with the amount of exhaust gases your engine and turbo are producing, causing a dangerous spike in boost levels. This is often referred to as boost creep or overboost and can be very dangerous especially during tip-in or when the boost first begins to build, which is usually lower in the rpm range.
The exhaust port for the internal wastegate can also become cracked or damaged over time leading to problems building boost. A cheap solution is to weld the internal wastegate shut and install an external wastegate somewhere on the manifold or collector.
Welding an external wastegate onto your manifold like our 4G63 here will help alleviate any issues you have with overboost.
Welding an aftermarket external wastegate onto your manifold allows you to choose from a multitude of available port sizes, from 38mm all the way to 65 in some cases. Some larger turbos demand the use of two external wastegates to help curb the boost to controllable levels.
Products like the Tial external wastegates take boost control to the next level

It’s not hard to imagine an time when the external components of a turbocharger like the external wastegate or blow off valve will become obsolete. Turbochargers like the Borg Warner EFR incorporate the best of all worlds, giving the true performance enthusiast the total package in a compact form factor.

Borg Warners EFR line of turbos is changing the game
Borg Warners EFR line of turbos is changing the game

Whatever style of boost control your vehicle happens to use, just remember that control of boost and predictability gives you a reliable base to build upon.

We hope this shed some light on the discussion of Internal vs External Wastegates, please let us know if you have any questions or comments below.

Happy Boosting!