Work cycle: The conversion of thermal energy and mechanical energy of the internal combustion engine, through the piston in the cylinder, continuous intake, compression, power and exhaust processes. The process of each machine is called a work cycle.

Piston stroke: The minimum linear distance between the top and bottom dead center, known as the piston stroke (or piston stroke), the minimum linear distance between the center of the crankshaft and the connecting rod's big end to the center of the crankshaft's rotation is called the crank's rotation radius.

Top dead center and bottom dead center: When the piston moves in the cylinder, the highest point is called top dead center (or top dead point), and the lowest is called bottom dead center.

Work volume: The piston moves from top dead center to the next point, called cylinder volume (piston displacement).

Compression ratio: The air fills the cylinder, and the total volume occupied by the cylinder will occupies the total volume of the cylinder. The greater the gas compression ratio is, the more the gas is compressed when the piston moves, and the higher the temperature and pressure of the gas, the internal combustion engine The higher the efficiency.