What are four-stroke and two-stroke engines?

2-stroke means that the crankshaft can complete a working cycle once, that is, intake (2-stroke is called scavenging)-compression-work-exhaust. This is the characteristic of a two-stroke engine.

The characteristic of a four-stroke engine is that the crankshaft rotates twice to complete a working cycle, that is? Inhalation-compression-work-exhaust (junior high school physics is called inhalation stroke-compression stroke-work stroke-exhaust stroke).

note:

The engine cylinder is equipped with a piston, which is connected with the crankshaft through a piston pin and a connecting rod. The piston reciprocates in the cylinder, and the connecting rod drives the crankshaft to rotate, transmitting power to the automobile.

When the piston reciprocates, the stop point when the top surface of the piston is farthest from the crankshaft centerline is the top dead center, and the point where the top surface of the piston is closest to the crankshaft centerline is the bottom dead center. The distance between the top and bottom dead centers is the piston stroke, and the crankshaft rotates 180 degrees per piston stroke. The working cycle of a four-stroke engine is divided into four strokes: intake stroke, compression stroke, power stroke and exhaust stroke.

air suction stroke

The carburetor, throttle (single-point injection) and intake port (multi-point injection) of gasoline engine outside the cylinder mix air and gasoline to form combustible mixture, which is then sucked into the cylinder.

In this process, the intake valve opens, the exhaust valve closes, the piston moves from top dead center to bottom dead center, the cylinder volume above the piston increases, and the pressure in the cylinder decreases. When it is lower than atmospheric pressure, vacuum suction is formed in the cylinder, and combustible mixed gas is sucked into the cylinder.