Understanding Turbochargers, Superchargers and Intercoolers

Modern automotive engineering innovations utilize various types of forced induction components like turbochargers, intercoolers and superchargers. Many are perplexed as to the differences between them and the benefits to performance that each presents. Let's examine the concept of forced induction in general as well as each of these three components:

Forced induction is the term used to describe the mechanical aspiration of an engine - specifically an internal combustion engine. A compressor is added to the air intake system to increase the amount of oxygen taken in. This enhances the vehicle's capacity for combustion, thereby increasing power output. From an engineering viewpoint, it is a simplistic addition.

Besides increased power, increased engine efficiency and decreased emissions result from a forced induction air intake scheme. A given amount of fuel (gasoline) has a given capacity for energy creation. The number of cylinders in an engine is also fixed. With given values for fuel volume and cylinder number, the obvious way to increase power is to increase the volume of oxygen inside of each of the cylinders. This is premise of forced induction.

Turbochargers are air compressors driven by exhaust-powered turbines. The turbine and the compressor are joined together via a common axle. It is the exhaust gases from the engine's combustive processes that drive the turbine's wheel. When the wheel of the turbine rotates, it causes the compressor to drive surrounding air into the intake manifold. This in turn increases the oxygen in each of the engine's cylinders and results in increased engine power.

Superchargers step the aspiration process up by utilizing a compressor that is directly driven by a belt, chain or gear/shaft combo stemming form the engine's crankshaft. Superchargers are often referred to as blowers and you will hear them when they engage - a droning, winding, humming sound is produced. The result, as with a turbocharger, is an increased amount of per-cylinder oxygen which is one of the 3 components needed to create combustion. The other two are a spark from the plugs and fuel (gasoline).

The Combined Gas Law is a mathematical law that states basically that compressing air raises its temperature. That is just a fact. So when a turbocharger or supercharger is utilized to increase engine power, the increased amount of oxygen entering the air intake manifold is hotter than normal. This heated air can cause pre-ignition of the fuel source, otherwise known as an engine "knock". Knocking is undesirable. The solution is called intercooling.

Intercoolers are mechanical devices, either fueled by atmospheric air or liquid, that reduce the temperature of the air that is being forced into each cylinder. The result is a more dense intake charge. This results in an increase of combustion capacity per engine cylinder. The process is known as isochoric cooling.

This provides a basic overview of the forced induction processes. Of course, the actual physics of the concept is far more perplexing. It is notable that the vast majority of vehicles produced today utilize at least a single-stage supercharger system. Forced induction technologies were handed down by the aeronautics industry to boost the performance of land-based vehicles.