Turbocharging
Turbocharging an engine occurs when the engine's own exhaust gasses are forced
through a turbine (impeller), which rotates and is connected to a second impeller
located in the fresh air intake system. The impeller in the fresh air intake system
compresses the fresh air. The compressed air serves two functions. First, it
increases the engine's available power by increasing the maximum amount of air
(oxygen) that is forced into each cylinder. This allows more fuel to be injected
and more power to be produced by the engine. The second function is to increase
intake pressure. This improves the scavenging of the exhaust gasses out of the
cylinder. Turbocharging is commonly found on high power four-stroke engines.
It can also be used on two-stroke engines where the increase in intake pressure
generated by the turbocharger is required to force the fresh air charge into the
cylinder and help force the exhaust gasses out of the cylinder to enable the engine
to run.
Supercharging
Supercharging an engine performs the same function as turbocharging an engine.
The difference is the source of power used to drive the device that compresses the
incoming fresh air. In a supercharged engine, the air is commonly compressed
in a device called a blower. The blower is driven through gears directly from the
engines crankshaft. The most common type of blower uses two rotating rotors
to compress the air. Supercharging is more commonly found on two-stroke
engines where the higher pressures that a supercharger is capable of generating
are needed.
