Engine Parts and Operation

Most of today's automobiles use spark-ignited four stroke reciprocating gasoline engines. A limited number of cars use diesel engines. A reciprocating gasoline engine has a round piston in a cylinder, a connecting rod, and a crankshaft. The principle of its operation is simple. The piston moves up in the cylinder, compressing a mixture of air and fuel in front of it. Compressing the air and fuel makes it very flammable. When the piston reaches the top of its travel, the air-fuel mixture is ignited. As the piston is pushed down in the cylinder by the expanding gases, it pushes on the rod, forcing the crankshaft to rotate. Power is taken from the rotation of the crankshaft to propel the car. As the crankshaft turns, the piston is returned to the top of the cylinder to repeat the cycle again. The continuing up-and-down motion of the piston is why the engine is called a reciprocating engine.