A turbocharger is an easy way to get a significant amount of extra power out of an engine.
It is, in essence, two fans connected by a rod, all encased in a housing. One of these fans sits in the airflow of the engine’s exhaust, while the other sits in the engine’s air intake. As the engine is revved, it produces more exhaust gases (put your hand near a car’s tailpipe to feel this effect).
These gases spin the fan in the exhaust, which in turn spins the one in the intake, thereby dragging in more air and forcing it into the cylinders, giving more power.
However, turbocharging is not perfect, because while it draws in more air to the engine, it also means that more fuel is required to create the power increase, so a turbocharged engine will use more fuel than a naturally aspirated engine of the same size.
In addition, turbocharging heats up the air, which makes it less dense, reducing the efficiency of the combustion process.
That’s why manufacturers also fit intercoolers, which cool the compressed air after it leaves the turbo and before it enters the engine.
There’s also the issue of turbo ‘lag’. This occurs at low revs, because the engine isn’t revving hard enough and generating a big enough volume of exhaust gases to drive the turbo.
Once revs reach a certain level (usually around 1600rpm) the turbo suddenly comes into operation, generating a surge of power, which can make the car tricky to drive.
However, modern electrics have managed to compensate for this to a great extent.
Where turbocharging really wins is that it allows the use of smaller engines in common family hatchbacks.
These can be boosted to generate the same power as a larger engine, but because they’re smaller they use less fuel than the larger motor.
They are also much lighter than larger engines, further helping fuel economy.