Turbocharger: What It Is and How it Works

Cars equipped with turbochargers enjoy a higher power and lower consumption: let's discover more.

The majority of new car engines are equipped with a turbocharger, an element that reduces engine cubing and emissions. Its function is to recover part of the energy of the exhaust gases and to use it to overburden the engine. Let's see how it works in detail.

How it works

The turbocharger consists of two elements, the turbine and the compressor, equipped with pallets and connected by a shaft. The turbine comes into operation thanks to the exhaust gas, while the compressor is activated by sucking the air to be compressed.

The compressor allows you to raise the air pressure in suction and implement the jet to the combustion chambers. A certain amount of energy is required to perform this operation. This is supplied by the turbine that recovers it from the exhaust gases. The gases coming out of the combustion chamber are conveyed from the exhaust pipes to the turbine, which starts turning by moving the compressor that sucks air and compresses it.

Thanks to the greater quantity of air reaching the cylinders, together with an increase of the injected fuel, an engine equipped with a turbocharger can boast an increase in torque and much higher power rating compared to an engine aspirated with equal displacement.

Variable geometry turbocharger

One of the weak points of turbocharged engines is the so-called "turbolag". This term refers to the delay in response of the engine at low speeds. Anyone who has ever driven a car with a turbocharger, in fact, has noticed that sinking the foot on the accelerator takes a few moments before the engine responds.

In order to reduce this effect, devices such as the variable geometry turbocharger have been adopted. This is characterized by a snail of the turbine that opens on the impeller thanks to a series of mobile Wings placed on a ring that allows them to move at the same time.

When the rotational speed is low, the flaps remain closed so that the gas can accelerate faster and can increase the thrust on the turbine, while when the rotation speed rises the flaps are open, producing a reduction of the back pressure.

The adjustment of the wings can be controlled by a vacuum valve on the inlet pipe, or by an electric movement managed by an electronic control unit.

Electric turbocharger

The technological evolution has allowed to develop new types of turbocharger able to stress less the engine. These include the electric turbocharger or a device powered by an electric motor and not by exhaust gases that allows the engine not to suffer the stress typical of the "classic" turbocharger.

This technology, currently used on high-end sports cars, will soon also be available on standard cars for all motorists. Manufacturers such as Audi are studying electrical solutions that can reduce, if not cancel, the turbo lag, thanks to the presence of a turbo-compressor driven by an electric motor connected to a battery of 48 V and a turbo classic. The first one comes into action when traveling at low speeds and has the function of sending air in to the standard turbocharger.

Another advantage of the electric turbocharger is to increase the engine power without affecting consumption.

Volumetric turbocharger

Another type of turbocharger present in the world of the car is the volumetric turbocharger. This system, unlike the exhaust gas system, operates through a mechanical connection to the engine. The compressor uses the power of the propeller to compress the air and then send it to the cylinders.

The direct connection with the engine also implies a linear increase in power as the air mass is connected to the speed of rotation of the propeller.

This direct connection, then allows an engine equipped with a turbocharger, volumetric is not subjected to the turbolag, but unlike the other models listed above is penalizing in terms of power consumption because it fails to take advantage of the exhaust gases, but absorbs energy from the engine and therefore has a lower yield as compared to a naturally aspirated engine or a turbo classic.