Machines which apply power to do work and convert various forms of energy into mechanical forces and motions; such as, automobile engines, that use internal combustion to create the movements of vehicles.

A type of engine that compresses the air before the fuel is injected so it ignites without the need for a spark plug.

Diesel engines burn heavier oil than gasoline, and are more efficient than gasoline engines. They produce high torque at relatively low speeds which is ideal for trucks and buses.

An engine that burns fuel inside closed metal cylinders.

External combustion engines; such as, steam engines, produce power less efficiently by burning fuel in an external chamber to heat a liquid or gas, which then moves a piston or a turbine.

Each piston in an internal combustion engine makes four "strokes"

The four-stroke cycles include explosions inside the engine's cylinders, on top of the pistons, and the blast force pushes the pistons down; then, the crankshaft swings around and pushes the pistons back up for the next stage in the cycle. The cycles for one piston are described in the following sequences:

1. The piston moves down, sucking in air through the inlet valve while a tiny squirt of gasoline is injected into the air.
2. The inlet valve at the top closes, trapping everything inside and then the piston moves up, squeezing the air and gasoline tightly together.
3. When the piston reaches the top, a carefully timed spark sets fire to the gasoline; as the gas burns explosively, forcing the piston back down.
4. Finally, the piston moves back up and pushes the burned gases out of the outlet valve which leave the car through the exhaust.

An engine that makes power by burning a continuous stream of fuel and air.

A jet engine moves a plane or car forward by firing a stream of hot gas backward; a scientific idea known as action and reaction or Newton's third law.

An engine fueled by coal or oil that heats water to make steam.

The steam pushes pistons back and forth to drive one or more wheels.