05 May 2020
SUCK. SQUEEZE. BANG. BLOW: The beginner’s guide to turbos

Turbocharger – it is a word you would have most certainly come across. Maybe you’ve seen it in advertisements or heard it on TV? In fact, despite being an automotive term, ‘turbo’ been widespread enough to enter the popular English lexicon. But what is a turbocharger (or turbo for short) exactly?

Mitsubishi Evo – autoapp
A bevy of high-performance turbocharged Japanese cars.

What is a turbocharger?

Here’s all you need to know to get up to speed (hur hur) on turbochargers!

There are plenty of ways to improve a car’s performance, and turbos are one of the most potent and cost-effective. It’s a device that crams more air into an engine, which then allows more fuel to burn, creating more power.

If you have seen a satay seller fanning the charcoal embers, the turbocharger does the job of the fan.

satay man fannimg –  autoapp
Satay seller fanning the flames.

Originally developed to mitigate the power loss of aeroplane engines at high altitude, turbos started to appear in sports cars since the mid-1960s. These days however, turbochargers are found in all sorts of vehicles. From tiny hatchbacks to the biggest SUVs, because it turns out they boost not just performance, but economy and emissions as well.

Man holding a turbocharger – beginner’s guide to turbos - autoapp
Women want diamond rings, men simply want more power.

How it works

Remember the TV show Top Gear? Jeremy Clarkson once provided a very succinct explanation on how turbos work: “Exhaust gases enter the turbocharger and spin it, witchcraft happens, and then you go faster”.

That makes it sound devilishly complicated, but it isn’t. That said, to understand how a turbo works, we first need to know how engines work, and for that, there’s a simple phrase to remember: Suck, Squeeze, Bang, Blow. I promise that isn’t a kinky bedroom routine.

Suck: Engine draws in air and fuel. Non-turbocharged engines are naturally-aspirated.
Squeeze: The mixture of air and fuel is compressed to a high pressure.
Bang: Spark plugs ignite the air/fuel mixture. This mini-explosion and rapidly expanding gasses provide the force that powers the engine, and thus the car.
Blow: The spent gasses spin the turbocharger before leaving the exhaust pipe.

turbocharger – beginner’s guide to turbos– autoapp
It may look like a snail, but a turbocharger has attributes that are quite the opposite.

Turbochargers – which ironically look like snails – derive from the Latin word “turbo”, or spinning top. They contain two turbines connected by a shaft. Exhaust gasses – which would otherwise be wasted – are passed through the turbo on their way out of the car, spinning one turbine; meanwhile, at the other end of the shaft, the other turbine draws in fresh air, compresses it, and forces it into the engine.

Because there’s more oxygen, the engine can take on more fuel too, creating a bigger Bang and thus producing more power.

Subaru Impreza WRX – beginner’s guide to turbos - autoapp
Turbocharged engines get really hot, so huge air vents and scoops are needed to help cool the engine bay down.

Pros and Cons of turbocharging

The biggest advantage of a turbo engine is its potential for more performance. But another derivative of that is the ability to produce the same power as a naturally-aspirated engine, but more efficiently. With a turbo, carmakers can give you the same performance with a smaller engine, thus saving fuel and reducing emissions.

As they are a separate system to the engine, turbos add cost and complexity. Because they involve hot exhaust gasses, lubrication and cooling are crucial considerations as well.

Finally, because the turbo only works if there’s a sufficient volume of exhaust gasses flowing through the turbine – i.e. the engine needs to be running at a certain RPM – it also makes the throttle less responsive to your inputs. This is turbo lag.

Mercedes-AMG A45 S - autoapp
Fun fact: The Mercedes-Benz A45 is the most powerful turbocharged 4-cylinder engine (416 bhp) ever produced to date.

Conversely, naturally-aspirated engines contain fewer parts so are generally more reliable and cheaper to maintain, and their instant throttle response is more predictable for fast driving.

Turbocharging is just one way of cramming more air into a combustion engine and belongs to a larger classification known as forced induction that also includes supercharging. Very simply put, a supercharger also concentrates a larger volume of air than an engine could on its own. the only difference is that it is powered by a mechanical belt rather than exhaust gases. The benefit of this instantaneous boost since the turbines spin along with the engine when it’s running.

Nissan Note 1.2 DiG-S - beginner’s guide to turbos – autoapp
The Nissan Note 1.2 DiG-S has a supercharger fitted to its 3-cylinder engine

The downside of supercharging however, is that at higher speeds, they are not able to cram exponentially more air the way turbochargers do as the engine revs climb.

Turbocharging v Supercharging

To make things even more interesting, there are engine with multiple turbochargers; two, three and even four turbos working in tandem to make lots of horsepower and torque.

Or how about combining the both a supercharger and a turbocharger. Volkswagen has produced several models with both forms of forced induction and termed it twin-charging. The idea was to combine the advantages supercharging and turbocharging with none of the disadvantages. As turbocharging technology advanced, engineers were able to achieve performance, fuel consumption and exhaust emissions objectives with simpler turbocharging solutions.

VW Polo GTI – beginner’s guide to turbos – autoapp
The previous generation Volkswagen Polo GTI had a 1.4-litre engine that was both supercharged and turbocharged.