How an engine works begins with how it is built. Inside your there are cylinders that contain pistons that move up and down inside these cylinders. This motion creates what is called mechanical energy, which is then transferred to other components in the car/truck that power the engine and electronics.

You may have heard engines referred to by the term internal combustion. You may be thinking, “Combustion? Doesn’t that mean explosion?” You would be correct! Engines work by creating small explosions that are designed to convert the chemical energy in your car/truck’s fuel into the mechanical energy needed to power the engine.



The process of creating the explosion is called the compression stroke. A mixture of fuel and air is compressed by the piston near the top of the cylinder to begin the reaction that pushes the piston down. Next, the mixture is ignited. In gasoline powered engines, the mini explosion is ignited by spark plugs. In diesel powered engines, air is added and compressed prior to injecting the fuel. The compressed air heats up, so when the fuel is added, an explosion occurs.

The power comes from what is called a power stroke or combustion stroke. This is when the exploding air pushes the piston down, which is the motion needed to do useful work. It is the same motion that you use when pedaling a bike or pumping up tires. This stroke creates so much energy that there is enough inertia (an object in motion, stays in motion) to move the piston back to the starting position. This process happens over and over to power the engine.

You may have also heard the term Four Stroke Engine before. Most automobile/truck engines are Four Stroke Engines. Two of the strokes (steps in the reaction), compression and power, have already been discussed. However, there are two other components to this reaction. Just after the power stroke, there is an exhaust strokethat releases the byproducts of the chemical  reaction into your vehicle’s exhaust system.

After the exhaust stroke, there is an intake stroke. This pulls the air into the cylinder, so that that the compression stroke can ignite the mixture. The process is very similar to when you breathe. In gasoline powered engines, the fuel is added during the intake stroke.

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Written by:

Beckie Bean

Digital Content Coordinator at Country Truck & Auto

October 6, 2016

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