Two-stroke engine

Internal combustion engines are used to produce mechanical power from the chemical energy contained in hydrocarbon fuels. The power-producing part of the engine’s operating cycle starts inside the engine’s cylinders with a compression process. Following compression, the burning of the fuel-air mixture releases the fuel’s chemical energy and produces high-temperature, high-pressure combustion products. These gases expand within each cylinder and transfer work to the piston, producing mechanical power to operate the engine. Each upward or downward movement of the piston is called a stroke. The two commonly used internal combustion engines are the two-stroke and the four-stroke engines. A two-stroke engine performs compression, power, exhaust and intake in just two piston strokes. The simplest two-stroke engines do this by using the crankcase and the underside of the moving piston as a fresh charge pump. This engine has a power stroke, in each cylinder during each revolution of the crankshaft. The exhaust and the charging processes occur simultaneously as the piston moves through its lowest or bottom centre position. Two-stroke engines are ideal in applications such as chainsaws, weed trimmers, outboard motors, off-road motorcycles, and racing applications because they are generally less expensive and lighter than four-stroke engines.