Car Advice

How does a turbocharger work?

15 Oct 2018

Dave Morley 1

Turbochargers are becoming more common as a way of getting more power out of smaller engines but how does a turbocharger work?

You’ve just lit a campfire. But the kindling is a bit damp and it’s struggling to catch. What do you do? Yep, you blow on it. And suddenly those faint little hints of flame roar to life and before you know it, the whole collection of sticks is blazing away merrily.

That, in a nutshell, is precisely what a turbocharger does for your engine. Blowing on a fire works by adding more oxygen, and that’s what a turbocharger brings to the party happening under your bonnet. And as the campfire example shows, more oxygen equals a bigger fire. Or, in the case of an engine, a bigger bang and that means more power.

Fundamentally, a turbocharger is a fan. It’s driven by the flow of gas through the car’s exhaust when the engine is running and that’s energy that would be lost out the tailpipe if no turbocharger was fitted. So it’s the best kind of performance enhancer, because (aside from the cost of the turbo itself) it’s free to run.

As the exhaust gasses spin the turbo, the fan part of the turbo blows extra air into the engine. The car’s computer can then add more fuel to keep the correct ratio of air and fuel (for cleaner burning) and suddenly, the same engine is making more horsepower. Done properly, a turbocharger can allow a small capacity engine to make the power and torque of a much bigger engine.

Smaller engines are also lighter, easier to package physically and, for the majority of the time when the driver isn’t using the extra performance of the turbo, the fuel economy of the smaller capacity engine is maintained. Win, win. The only catch is that a turbocharger is no good for toasting marshmallows.

Practical Motoring will be regularly producing easy explanation articles like this one to help improve your motoring knowledge. If there’s a topic you’d like to see covered, leave a comment below and we’ll add it to the list.