How Does an Internal Combustion Engine Work?

Basically, an internal combustion engine burns its fuel source inside the engine. It does this by igniting a small amount of fuel (in the case of car engines, the fuel is gas) which then causes an “explosion”. This small “explosion” or combustion, releases a tremendous amount of energy and the energy is used to propel engine parts. In the case of cars, the engine parts that have been set into motion by the combustion make the car move. The energy released by the “explosion” is considered chemical energy. Once that chemical energy has made a mechanical part move, it has been transformed into mechanical energy.

Using a Combustion Chamber to Control the Explosion

The small amount of fuel that is ignited to create chemical energy is done so by putting intense pressure on the fuel and an oxidizer (which is something that makes the fuel unstable and causes it to explode). In most internal combustion engines, this process occurs in a combustion chamber. Creating the “explosion” in a chamber allows us to direct the chemical energy created to a specific place. So in a car, the chemical energy is transferred by pistons that turn the chemical energy into mechanical energy and start the whole process of making the car “go”. In a gas powered chainsaw, the chemical energy is transferred to cutting blades. Here is a 3D animation video of how an internal combustion engine works in a car.

Different Types of Internal Combustion Engines

Not all internal combustion engines are the same. Some are quite simple, like a two-stroke engine, which would be used in small bikes, water crafts like jet skis, and hand-held machines like chainsaws and lawn-edgers. A four-stroke engine is a bit more complicated and it is typically much larger. Cars and large machinery like tractors and cranes, use four-stroke internal combustion engines.


The two-stroke engine is generally smaller and less expensive. Usually people interested in engines first learn about internal combustion engines by taking apart a two-stroke engine. The two-stroke engine shouldn’t be viewed as a stripped down four-stroke. It has many components which are unique to it, such as employing a one-way reed valve between the air-fuel (gas) intake and the crankcase (combustion chamber). Once the air-fuel mix is in the crankcase, it is trapped there by the reed valve. Two-strokes also don’t have valves. They have ports or holes which control how much pressure is in the crankcase. So once air-fuel mixture is in the crankcase, pistons will block the exhaust ports and pressure inside the crankcase will increase, causing an “explosion” and starting the internal combustion engine.

internal combustion engine


Four-stroke engines are usually large and they are the most often used internal combustion engine for cars. They are also used for heavy machinery like gas-powered generators. In a four-stroke, a piston moves down, drawing air-fuel mixture into the cylinder (combustion chamber). The piston then moves up, engaging a spark plug which ignites the air-fuel mixture. The chemical energy released (in the form of a gas) expands and expands until the piston is forced down. Finally, the piston shoots back up and the chemical energy is forced out of the combustion chamber and is turned into mechanical energy. Even though the four-stroke engine is heavier, larger and more complicated than the two-stroke, it is actually a more efficient engine.for more details, follow this link.

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