How Does a Turbocharger Work?
- How it works
- Exhaust
- Engine
FixMyCar explains what a turbocharger is, what it does and how it works.
Book car repair nowEllie Dyer-Brown
Thursday April 04 2024
8 min read
Although turbochargers are common in modern petrol and diesel cars, they were initially designed for use in aviation and weren't fitted to cars until the 1960s. They became popular two decades later, in the 1980s.
You might already know that turbos deliver more engine power, but what exactly are they, and how do they work? This guide explains everything you need to know.
Contents
What does a turbocharger create?
What is a turbocharger?
Car engines work using internal combustion. Heat, fuel and air are combined in each cylinder to produce lots of tiny controlled explosions. Increasing one of these elements also increases the size of the explosion. The result is improved efficiency and power.
A turbocharger works on this basis. It is a device that uses the flow of exhaust gases to power a turbine wheel, compressing air and forcing more of it into the engine. Extra fuel is injected simultaneously to increase the strength of the combustion.
Bigger engines use more fuel to increase their power, but this comes at a cost - specifically, much higher costs at the garage forecourt. Turbos partially solve this problem because you can use them to generate more power from a smaller engine. They are only activated at certain speeds and work harder as engine revs increase. If you drive gently, the turbo may not be activated at all, making achieving a decent fuel economy easier.
How does a turbocharger work?
A turbocharger has two main sections: the compressor and the turbine.
The turbine
The turbine is, again, made of two parts: the turbine wheel and the housing. The turbine housing guides the exhaust gas into the wheel, turning it. The gas then exits the housing through an exhaust outlet.
The compressor
Similarly, the compressor has a compressor wheel and housing. A forged steel shaft connects the wheel to the turbine, and as the wheel turns at a high velocity, it draws in air and compresses it.
The compressor housing then uses a process called diffusion to turn the high-velocity, low-pressure air stream into a high-pressure, low-velocity air stream, which is pushed into the engine, allowing it to burn more fuel.
Turbochargers operate at incredibly high temperatures and pressures. For this reason, they are typically accompanied by an oil cooler, which ensures the lubricant doesn’t overheat, and an intercooler, which reduces the temperature of the turbo's air.
What does a turbocharger create?
Turbochargers create a greater amount of compressed air going into the engine. Extra fuel is injected alongside the air, producing more power.
Supercharger vs turbocharger
Like turbochargers, superchargers also increase an engine’s power by delivering more compressed air. However, supercharger turbines are spun by the engine rather than being spun by exhaust gases. They are belt-driven air compressors, which means - like a car’s aircon system - they are attached to the crankshaft.
Supercharger pros and cons
| Pros | Cons |
|---|---|
| Produces more torque | Uses more engine power |
| Lag-free | Less efficient |
| Sounds good | Burns fuel faster |
| Low RPM requirements | |
| Wider RPM range |
Turbocharger pros and cons
| Pros | Cons |
|---|---|
| More energy efficient | Needs coolant |
| Doesn't use engine power | Does not work at low RPMs |
| Uses waste energy to operate | Can get extremely hot |
| Provides more horsepower at higher speeds | Often has significant lag |
Why are so many cars turbocharged?
During light driving and official fuel economy testing, turbocharged cars can achieve impressive efficiency figures because the turbo only comes on at a certain rev threshold. This data makes vehicles with turbos an attractive option for manufacturers, who can lure in buyers with the promise of enhanced efficiency.
It is especially common for diesel cars to have turbochargers because they use simpler intake systems for mixing fuel and air and have more durable engine blocks that can handle immense pressure.
Fortunately, there have been technological advances over the last 15 years, with manufacturers perfecting a lightweight, alloy petrol engine block capable of withstanding ultra-high turbo pressures. Lighter cars are more efficient, so turbos have become more common in petrol cars since they no longer require a heavy steel or iron engine block.
The bottom line is that most vehicles with turbochargers can provide more power with lower emissions and better efficiency.
The benefits of a turbo
Turbochargers don’t just increase power. They also deliver more torque (the engine’s rotational force or strength). Small petrol engines often struggle to produce much torque at high revs, so adding a turbo can give them a boost.
By comparison, conventional diesel engines produce a lot of torque at low revs. When you add a turbo, it has an amplifying effect. If you put your foot down on the accelerator at 50 mph, a turbo diesel will have an instant and powerful response.
Another benefit of turbos is that they make the exhaust quieter by reducing the amount of gas leaving through the tailpipe.
The drawbacks of a turbo
Lag is the most significant drawback of turbocharged engines. It refers to the time delay between putting your foot down and when the turbo delivers extra power.
However, engineers have found clever ways of reducing lag in modern turbos. For example, some engines use an electric motor to spin the turbine before gases reach it. Others feature two or more turbos of different sizes that operate at different revs.
The other major drawback of turbos is that they can and do go wrong; when this happens, it’s expensive. Some engines are prone to turbo issues, so it’s worth researching common problems before buying your next car, which you can do by visiting the car ownership section of our blog.
Common turbocharger problems
Turbochargers can fail for several reasons.
Oil leak in turbocharger
Turbochargers rely on lubrication from oil because they spin incredibly quickly and experience enormous pressure. Due to this pressure, they are prone to oil leaks, which can be caused by damaged or worn seals and blocked pipes.
Oil delay
A delay in oil reaching the turbocharger due to a blockage can cause bearing failure and severely damage the system.
Contamination
Contamination of the oil circulating the turbo can damage bearings and cause blockages, resulting in turbo failure. This is one of the many reasons you should change your engine oil and filter regularly - a job that will also be done during your car’s annual full service.
Foreign material in air-filtration or exhaust system
Any foreign material that enters these systems, whether dirt or broken valve fragments, could damage the turbocharger and the engine.
Blocked DPF
A blocked diesel particulate filter can stop exhaust gases flowing through the system, preventing the turbo from operating correctly. Learn more about DPF problems and how to avoid them.
Leaking air intake system
A leak in the air intake system can put additional stress on the turbocharger as it tries to compensate for the lack of air.
Signs of turbocharger failure
Common signs of turbo failure include:
Whining sound
Increased oil consumption
Slower, louder acceleration
Difficulty maintaining high speeds
Can a turbocharger be repaired?
All Fords Ltd, an award-winning member of FixMyCar's Garage Network, explains why turbochargers are usually replaced rather than repaired:
"I don’t recommend repairing a turbo because it comes under so much strain. When garages order a replacement, it's often reconditioned, but that work has been done by an approved turbo specialist. Repairing a turbocharger on a bench is completely different. For a repair to be worthwhile, it must be done by a specialist who can test it thoroughly."
How much does it cost to replace a turbocharger?
According to FixMyCar’s data, the average price of a turbocharger replacement is £1,125.99.
"Turbocharger replacements are often quite expensive because the seals, gaskets and other components aren't made in the UK. They are usually assembled abroad, which makes the part itself cost more."
- All Fords Ltd, winner of 'Best Garage South East' at the 2024 Garage Awards.
As you can see from the table below, prices vary depending on the make of your car.
| Car make | Average price |
|---|---|
| Audi | £1,146.05 |
| BMW | £,249.11 |
| Citroen | £899.28 |
| Ford | £938.26 |
| Mercedes | £1,301.95 |
| MINI | £1,110.33 |
| Nissan | £1,013.53 |
| Peugeot | £896.05 |
| Renault | £1,044.25 |
| Toyota | £1,051.72 |
| Vauxhall | £950.74 |
| Volkswagen | £1,072.75 |
| Volvo | £1,207.23 |
The best way to get an accurate price estimate for your car is to request quotes from local garages on FixMyCar.
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