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Let's Get Wasted: Should You Choose An Internal Or External Wastegate For Your Turbocharger Build?

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When it comes to easily and substantially increasing the engine power of your vehicle, turbochargers are the weapon of choice for many motorists. However, while these devices may seem relatively simple at a glance they actually consist of a number of complex components, and making sure all these components work in harmony is vital if you want to get the most from your new turbo. One of the most important components of any turbocharger is its wastegate -- despite this, many motorists are unfamiliar with these devices and how they operate. 

What is a turbocharger wastegate?

Turbochargers draw their power from exhaust gases vented from the engine, which cause the turbocharger to spin up and subsequently increase the power produced by the engine. However, exhaust gases cannot be allowed to flow directly into an unprotected turbocharger -- if too much exhaust gas is allowed into a turbo, the excessive air pressure can cause significant damage to your turbo and potentially cause your entire powertrain to overheat.

Wastegates are used to solve this problems, and are placed in the the turbochargers exhaust inlet valve to regulate the flow of gases into the turbocharger. Once internal pressures inside the turbo reach a certain value, the wastegate activates and redirects the excess exhaust away from the turbo. 

Simple enough so far. However, turbo wastegates come in two different types -- internal and external -- which function in different ways and convey a different set of benefits to your vehicles powertrain. Deciding which type of wastegate is best for your turbocharging needs can be difficult, so make sure to familiarise yourself with their individual pros and cons before you choose a waste gate.

What are internal wastegates, and what are their pros and cons?

Internal wastegates are disarmingly simple, and consist of a simple valve built into the turbo's housing that releases unwanted exhaust gases back into your exhaust system, bypassing the turbo entirely. They are found on most stock and all-in-one turbochargers, and are very reliable devices in most circumstances. They also require very little piping to function properly (just enough to route excess gases further down the exhaust line), and are quite environmentally friendly since they re-route exhaust back into the exhaut manifold and catalytic converter.

The only real disadvantage of internal wastegates is that they can only deal with limited exhaust gas pressures and flow rates before they start to become sluggish. They are more than adequate for turbochargers fitted to most vehicles, but can impinge the maximum performance of high performance vehicles.

What are external wastegates, and what are their pros and cons?

Unlike internal wastegates, external wastegates are self-contained devices separate from the turbocharger itself, and are usually fitted to the exhaust manifold or header(s). Designed for high performance applications, these devices are more robustly built than their internal counterparts, but this is not their main selling point.

The chief advantage of choosing an external wastegate is that they can adapt to changing situations. Instead of simply venting excess gases back into the exhaust systems, external wastegates can vent gases into the exhaust system or directly into the atmosphere, depending on the engine's requirements. Taking unwanted gases out of the exhaust system entirely can dramatically increase airflow rates, subsequently leading to massive increases in turbocharged power for your vehicle.

However, peak performance will cost you. As well as being more expensive than internal wastegates, external wastegates are more difficult and time-consuming to fit, and will require significantly more piping to be installed. Venting gases into the atmosphere can also cause your vehicle to fall foul of strict emission limits, especially in urban areas -- as such, these wastegates are generally suited to track cars and other high-performance vehicles that aren't generally used for daily commutes.