Forced Induction

One of the more important characteristics of an engine is efficiency, the ability to get the most torque and horsepower with as little fuel as possible. Combustion engines have only two sources of fuel that require it to operate, these are oxygen and a combustible fuel source such as gasoline or diesel fuel. For the case of gasoline, inside the engine multiple chemical reactions take place separating the carbon and hydrogen molecules, but in order for this to happen oxygen must be present and readily available for the reaction to take place.

2C8H18 + 25O2 ~> 16CO2 + 18H2O

For combustion engines one of the better ways to make an engine more efficient is through the process of applying forced induction. Forced induction is the process of compressing more oxygen molecules into the engine so a more thorough burn of the combustible fuel source can take place. Simply, the more oxygen available during the reaction, the larger percent of the combustible fuel source actually combusts. There are two major ways two apply forced induction to a combustible engine, either turbo charging or supercharging the engine.

A turbo charger is a type of compressor attached to both the intake and exhaust manifolds. There is a turbine in the path of the intake manifold that compresses the air into the engine in addition to another turbine in the path of the exhaust manifold. There is a shaft connecting both these turbines so they spin at the same time. The intake manifold turbine is powered by the force of the exhaust gas leaving the engine through the path of the exhaust manifold turbine. Because of this turbo lag is a common factor with turbo chargers. The air cannot start compressing into the engine until the engine creates enough exhaust gas to start spinning the exhaust manifold turbine sufficiently. A supercharger is also a type of compressor but attached to the intake manifold only. This compressor is powered by the timing belt of the engine though so it is much more instantaneous and does not suffer from any lag.

When forced induction is applied to a motor addition cooling has to take place because when a gas is compressed, this results in an increase in temperature of the gas. Because of this intercoolers may have to be applied to the engine to sufficiently cool it and prevent any overheating of the engine. In the application of cars this means mounting intercoolers to walls of an engine bay, which increases the weight of the vehicle and also puts the center of gravity further from the center point of the car. In order to have a properly handing car, the center of gravity is best lowest to the ground and directly in the middle of the four tires so this is a sacrifice made to achieve higher horsepower and torque out of an engine.

The reason forced induction has been more popular lately is because of the lighter and stiffer chassis and frames that are able to be produced for cars today placing the center of gravity in a more desirable point. Even though forced induction is more popular today, it was actually invented before the combustible engine was. The patent for the super charger came from the air mover, which was used to blast furnaces with air for a larger burn for industrial uses. Dugald Clerk first used it on a two-stroke engine in 1878.