What is the engine working principle?

The engine works by converting other forms of energy into mechanical energy, two-stroke engines and four-stroke engines work differently, the vast majority of automobile engines are four-stroke. The work cycle of a four-stroke gasoline engine consists of four piston strokes, namely the intake stroke, compression stroke, work stroke and exhaust stroke. The intake valve opens, the exhaust door closes, the piston from the upper stop point to the lower stop point, the piston above the cylinder volume increases, generating vacuum, the cylinder pressure drops to the intake pressure below, in the vacuum suction through the carburetor or gasoline injection device atomized gasoline, and air mixture to form a combustible mixture, by the intake tract and intake valve into the cylinder. The intake process continues until the piston closes the intake valve past the lower stop, then the upward moving piston starts to compress the gas.