Superchargers and turbochargers are forms of forced induction. This simply means that they force more air into the combustion chamber of an engine. Because there is more air, the fuel can combust more completely, resulting in more power.
Superchargers are mechanically driven by a belt which drives a turbine.The turbine forces the incoming air into the cylinder. The increased air pressure means that there is more oxygen for the fuel to combust with. This results in a more complete, powerful combustion. It is often helpful or even neccesary to increase the amount of fuel delivered to the combustion chamber as well, which creates even more power. There are different types of superchargers, the most recent and best being the ones that have their own oil supply.
Turbochargers work on the same principle as superchargers, but they are driven by a turbine placed in the exhaust manifold of the engine. As the exhaust gases turn the turbine, they turn a second turbine that pressurizes the intake.
Forced induction in two-strokesEdit
Forced induction relies on engine valves to hold in the pressure. For this reason, they only work on four-stroke engines, and on some two-stroke engines with ports arranged in such a way that the intake port is the last to close. Some companies produce turbochargers that fit two-stroke RC engines, and they claim that they work well, but the truth is that because of the way the ports are arranged in RC two-strokes, the pressure is released out the exhaust port, thus negating any gains from increased pressure.