A auto engine is an internal combustion gasoline engine, which works on a four-stroke system: intake, compression, power, and exhaust. The four strokes are made by the pistons, which move up and down inside each of the cylinders of the enbgine. Each one cylinder has its own intake valve, exhaust valve, spark plug, and piston. Gasoline comes in from the gasoline tank through the fuel lines, and it mixes with air and is atomized. The air-fuel mix is what goes in the cylinders and make them move.

The intake stroke starts once the intake valve of a cylinder opens, letting the air-fuel mixture in. The piston slides downward inside the cylinder. This down movement produces a big vacuum, which helps sucking in the air-fuel mixture.

Both valves are closed while the compression stroke. The piston goes upwards, compressing the air-fuel mixture up in the direction of the spark plug. This compression produces the fuel more explosive for easier detonation.

Both valves keep on being closed on the power stroke. The spark plug explodes the air-fuel mix. The resulting blast dramatically forces the piston downward.

The exhaust stroke begins as soon as the exhaust valve opens. The piston is going upwards again, forcing the remaining side-effects of the burned air-fuel mix out in the exhaust system.

The pistons are attached with the piston pin and connecting rod to the crankshaft. The crankshaft is not straight, it has high and low points that help drive alternating pistons up and down. When the power stroke forces two of the pistons in a four cylinder engine down, it pushes on the crankshaft, which spins and simultaneously pushes up on the other two cylinders pistons. Everything is in constant motion, half the pistons travel up as the other half slide down.

The intake and exhaust valves are moved in the same way by the camshaft. The camshaft is as well joined by gears to a distributor. The spark plugs are attached to the distributor by plug wires. When the camshaft turns, opening and closing the valves, it in addition triggers the distributor, which causes the spark plugs ingnite at the right point in the cycle.

The crankshaft and camshaft are connected at the face of the engine by the timing chain or belt. This timing chain/belt must be correctly aligned in order for the system to operate in constant harmony, with perfect timing.

The flywheel is bolted to the back of the crankshaft. Once you turn the key in the ignition, the starter engages the gear on the flywheel. This starts the whole motion of the engine. After the cylinders ignite, the engine constantly moves itself with the four-stroke system.