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​How Does a Turbo Work on a Diesel Engine?

Apr 11th 2022

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If you own a modern diesel engine, your vehicle uses what’s known as a turbocharger. Virtually all modern diesel engines use this technology. The turbo compresses air as it goes into the combustion chamber, which increases engine power and performance. This component has become a staple of the diesel industry. Drivers have come to depend on the extra power that comes with turbos, but many still don’t understand how they work. Learn more about how turbos work on diesel engines and what happens when things go wrong.

What Is a Turbocharger on a Diesel Engine?

The turbocharger is designed to increase the amount of air going into the combustion chamber.

All diesel engines need air and fuel to power the engine. Naturally aspirated diesel engines use ambient air around the engine. The piston moves down, which allows air to pass naturally into the combustion chamber. They have a simple design, but they can only do so much to increase the amount of air going into the chamber.

Turbocharged diesel engines suck in additional air to increase engine power. The more air that enters the engine, the faster the fuel will burn, which gives the vehicle a boost. There’s typically a slight delay from the time you engage the turbo to when you feel the boost. This is what’s known as turbo lag. The system needs several seconds or more to properly compress the additional air that’s going into the combustion chamber.

So, how does a turbocharger work?

Once the air leaves the combustion chamber, it enters the turbine housing and moves the turbine wheel. The energy generated from the turbine wheel powers the compressor, which increases air pressure while reducing the velocity. The air then passes through an exhaust outlet before re-entering the combustion chamber.

Turbos can either be manual, automatic or a combination of the two. Automatic turbos will adjust the amount of air coming into the combustion chamber based on how much horsepower is needed to move the vehicle. Manual turbos give you more control. You can rev up the turbo whenever you need a boost. Hybrid systems let you turn the automatic functions on and off.

When you power up the turbo, you send a signal to the engine that you need to increase power. This requires additional air and fuel. Stepping on the gas will send more fuel into the combustion chamber as the turbo increases the amount of air. This increases the amount of exhaust gas, which then keeps the turbo moving.

Turbos are largely responsible for making sure there is the right amount of air in the combustion chamber. If there is too much air in the chamber, the exhaust gas will run hotter than normal. You will start to burn through more fuel than necessary as your aftertreatment cooling system works to reduce the temperature.

Using the turbo increases the flow of fuel, which puts extra pressure on your diesel particulate filters. These filters are designed to get rid of particles that can damage your engine components. Remember to replace your diesel particulate filters as needed to reduce wear and tear.

Shop Diesel Particulate Filters Online

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Fixed vs Variable Geometry Turbos

Diesel engines use either fixed or variable geometry turbos.

In a fixed geometry turbo, the turbine and compressor have set geometries. The flow of compressed air depends on the flow of exhaust gas. This means the turbo will either speed up or cool down based on operating conditions. They have a simple design and are relatively easy to maintain. Fixed geometry turbos are typically used in vehicles that maintain steady airflows, as the geometry cannot be changed.

Variable geometry turbos can adjust the geometries of the turbine and compressor based on driving conditions. The exhaust gas enters a series of sliding vanes. The turbo actuator will change the shape of these vanes to adjust the flow of exhaust gas going into the compressor. VGTs can help improve fuel efficiency by limiting the amount of air entering the combustion chamber.

You may need to replace your turbo actuators as you continue using turbo. The actuators run on electricity. If the system fails, the sliding vanes will default to 100% open. This will increase the amount of compressed air going into the chamber, which can decrease fuel efficiency.

The actuator on the 6.0 Powerstroke has been particularly problematic. Find replacement 6.0 VGT actuators online to improve engine performance.

Image Credits 

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