A turbocharger is a mechanical device comprised of a turbine connected to a compressor. Exhaust gases from the engine rotate the turbine on their way, which in turn rotates the compressor. This compressor now compresses fresh air and feeds it to the engine, thus achieving what a supercharger would achieve without the additional load on the engine.
Forced induction systems also contain a critical support system: the intercooler. As air is pressurized in the superchargers, its temperature rises, which can cause premature combustion inside the engine, which is detrimental to the engine’s integrity in the long run. Thus, pressurized air is passed through a heat exchanger that cools it before it’s fed to the combustion chamber. This process of heat exchange is known as intercooling.
Although turbocharging is a subset of supercharging, these terms find distinct usage in the automotive industry. While supercharging, per se, has become less frequent, the popularity of turbocharged setups is on the rise.
Advantages and disadvantages of supercharging (and turbocharging)
As it becomes possible to squeeze more air and fuel into the same space, you can get more power without having to invest in a bigger engine. However, this power comes at a cost, resulting from the inherent disadvantages of the construction of forced induction devices.
The most significant disadvantage comes in terms of reduced fuel economy, due to squeezing more fuel into the engine. To combat this disadvantage, engineers now equip cars with smaller engines to generate the same power as their larger counterparts, while employing forced induction.
For example, a car that was originally equipped with a 2-liter (capacity for air-fuel mixture) engine making 120 kW of power can produce the same power as a turbocharged 1.2-liter engine. Since the size of second engine is smaller, it will consume less fuel and keep the mileage from suffering.
The second disadvantage is that superchargers and turbochargers do not supply extra power immediately. This results from the moving parts of these devices not reaching full operating speeds immediately due to inertia.
While this gap in the power supply is barely perceptible in superchargers, it is quite prominent in turbochargers and is referred to as turbo lag. This has resulted in the development of multi-stage turbocharging, where smaller turbochargers are used for slower engine speeds, while bigger turbochargers are used for high engine speeds.
Current use and the future of forced induction
Forced induction finds use in both commercial and performance-based applications. For car manufacturers, it’s an easy way to deliver small engines that are compliant with safety and emission norms, while still providing a decently powerful car. In the performance and modification culture, it’s an inexpensive way of generating more power within an already powerful system.
The future of forced induction is bleak, however, as it’s destined to meet a very inevitable demise when the internal combustion engine disappears in the not-so-distant future!