Stringent emissions regulations throughout the world are challenging automobile manufacturers to create engines that meet the needs of the environment whilst still producing vehicles that are enjoyable to drive. Turbochargers meet that challenge and deliver significant benefits to end users, primarily offering more response, increased economy and reduced NOx and CO2 emissions. Turbochargers deliver greater torque, which, in turn, translates into improved performance on the road, making driving a real pleasure ...but how do they work?

In order to explain how a turbocharger works we must first look at the four-stroke cycle.

1. Suction (charge exchange stroke)

In a diesel or petrol injection engine, the piston moves down and air is drawn through the intake valve. In a carburettor petrol engine, the air is mixed with petrol.

2. Compression (power stroke)

As the piston moves back up, the air or petrol/air mixture is compressed.

3. Expansion (power stroke)

In the carburettor or injected petrol engine, the fuel/air mixture is ignited by a spark plug; in the diesel engine, fuel is injected under high pressure and the mixture ignites spontaneously. In either case, the explosion drives the piston downwards.

4. Exhaust (charge exchange stroke)

The exhaust gas is expelled through the exhaust valve when the piston moves up. In a turbocharged engine, the air is pre-compressed before being supplied to the cylinder during the suction stroke. Because it is at a higher pressure, a greater mass of air is held in the combustion chamber, which means that fuel is burned more efficiently. This increases the engine’s power output, giving more torque and a higher top speed compared to a normally aspirated engine of the same swept volume, and reduces emissions. Some diesel engines can also be set up to accept more air but the same amount of fuel, which does not increase the power but results in cleaner exhaust gases.

How the turbocharger works?

A turbocharger is basically an air pump. Hot exhaust gases leaving the engine after combustion are routed directly to the turbine wheel side of the turbocharger to make it rotate up to 230,000 rpm. That turbine wheel is connected by a shaft to a compressor wheel. As the turbine wheel spins faster and faster, it causes the compressor wheel to also spin quickly. The rotation of the compressor wheel pulls in ambient air and compresses it before pumping it into the engine's chambers.

Many systems will incorporate a cooler between the compressor and the cylinder, as the compressed air, moving at such high speed, can reach extremely high temperatures.

Not As Easy As It Looks

The basic principal behind turbocharging is fairly simple, but a turbocharger is a very complex piece of machinery. Not only must the components within the turbocharger itself be precisely coordinated, but the turbocharger and the engine it services must also be exactly matched. If they're not, engine inefficiency and even damage can be the results. That's why it's important to follow correct installation, operating and preventative maintenance procedures.