Super Charger

A super charger was developed for speed freaks who wanted to make their cars go faster. It works on the principle of forced induction system. It’s one and only purpose is to make a car go faster.

Ever since the invention of the automobile, enthusiasts, engineers and speed junkies have been trying to make the car go faster and faster. A car can be made to go faster by a bigger or more powerful engine. But this costs more also it is more heavy which reduces the power to weight ratio of a car. The other way of increasing the power output of an engine is by adding a supercharger to a normal engine to boost power.

Supercharging is a method of forcing more air into the combustion chamber which has come to be known as forced induction system. A supercharger is powered mechanically by a belt or chain drive from the engine’s crankshaft. In essence what the supercharger does is suck more air into the cylinder which is combined with more fuel supply leading to a bigger explosion which results in higher power output and torque which makes a car go faster. On an average supercharging adds 46% more horsepower and 31% more torque. At sea level a typical boost from a supercharger places about 50% more air into the engine.

The trouble is, as the air gets compressed it gets hotter which means it loses its density and cannot expand during explosion. This means that it does not produce as much power under explosion. AS a result an intercooler is used to cool the compressed air before it goes into the intake manifold. It works like a radiator where cool air or water is passed through a system of pipes. When the hot air encounters the cooler pipes it cools down. This increases the density of the air which creates a denser charge upon entering the combustion chamber.

There are three types of super chargers: Roots super charger, Twin-screw super charger and Centrifugal super charger. Each uses a different way to move air to the intake manifold of the engine.

The Roots supercharger is the oldest design. It uses meshing lobes to spin air from the fill side to between the lobes and then to the discharge side which leads to the intake manifold of the engine. Large quantities of air move into the intake manifold and stack up to create pressure. Roots superchargers are large and sit on top of the engine. They are usually used in muscle cars and hot rods. They are the least efficient type of supercharger as they add a lot of weight to the car and provide busts of air instead of a smooth and continuous flow.

A twin screw supercharger works by pulling in air through a set of meshing lobes that resemble the groves on a screw. A twin screw supercharger compresses the air inside a rotor housing. The air pockets decrease in size as they move from fill side to discharge side which leads to the intake manifold of the engine.  As the air pockets shrink, the air is squeezed into a smaller space. This makes twin-screw superchargers more efficient, but they cost more because the screw-type rotors require more precision in the manufacturing process. Most twin-screw superchargers sit on top of the engine.

A centrifugal supercharger powers an turbine which draws in air at very high speeds into a small compressor housing which then sends it outwards towards the intake manifold.  Air leaves the impeller at high speed, but low pressure. A diffuser (a set of stationary vanes that surround the impeller) converts the high-speed, low-pressure air to low-speed, high-pressure air. The air slows down when it hits the vanes which reduces the velocity of the airflow and increases pressure. Centrifugal superchargers are the most efficient type of supercharger. They are small, lightweight and attach to the front of the engine instead of the top.

Superchargers do not suffer from lag as it is powered by the engine. On the downside, because superchargers use power from the engine they decrease its efficiency. Roots and twin-screw superchargers provide more power at lower RPM while Centrifugal superchargers provide more power at higher RPM.