Superchargers contain roller and needle bearings. This is because they rotate in excess of 10,000 rpm. They are belt driven by the engine’s crankshaft. Turbochargers are driven by the vehicles exhaust. This is why so many consider a turbocharger a free source of boost. This is different from a supercharger that takes a little power from the engine to create additional boost. It’s a great deal because they increase horsepower by ~20 %. This means that a supercharger can make a 300 hp engine produce 360 hp.
Most superchargers are roots-type, positive displacement pump. They contain a pair of two or three lobed vanes that turn as the engine turns. As the vehicle is accelerated, they turn in opposite directions of each other. This turning motion pulls air from its inlet and forces it into the engine cylinders. Before entering the intake, this pressurized air is cooled by an intercooler. Heat is created by air squeezing through the tight gap in the vane lobes. This cooled charge increases the vehicle’s performance and horsepower.
On many superchargers, changing the size of the pulley changes the speed at which the blades turn. The front bearings contain an opening and a removable dipstick or plug to check and service the special high speed lubricant. Depriving a bearing of its necessary lubricant will result in damage and a noisy squeal.
Some of today's OEM superchargers are driven by a computer controlled electric motor. These superchargers are very precise; engine computers operate valves and adjust boost. It may turn the boost on and off as required. These superchargers are far more efficient than standard superchargers that operate under all conditions.