Four easy steps to an internal combustion engine.
Everyone who has a car obviously knows that it is the engine that makes the car go. But what everyone does not know, is what makes the engine work. Engines are complex mechanical devises, but each one needs the four basic steps to accomplish anything. To explain these steps to you lets use a more basic engine. Lets use a 1985 Chevrolet 350 small block, a very basic engine with only 18 valves and a carburetor. To make this beast work you need, intake, compression, ignition, and exhaust.
First the piston start at the top (top dead center) of the cylinder and draws down. This sucks a mixture of gasoline and air into the cylinder. This is done by one of the two valves opening and allowing the gas and air to flow freely. Once the piston has reached the bottom of its travel (bottom dead center) the correct amount of gas and air has been drawn in. At this point the valve closes and it is now ready for compression.
The compression stroke is when the piston goes from bottom dead center and moves up to compress the air and gas mixture. This causes the mixture to become more flammable and thus give you a stronger burn. Once the piston has reached the top the gas and air have completely mixed and it is very hot because of all of the friction between each other. Now It is ready for ignition.
Next the ignition stoke comes. This consists of the spark plug firing and igniting the pressurized gas. Now contrary to what people think this is not an explosion, this is rather a very hot and very powerful burn. This burn causes the gas to expand forcing to piston down. When this happens the power from the burn transfers to the crank shaft which is connected to the transmission, thus resulting in the car moving. Now all the burn gasses must evacuate the cylinder.
Now lastly the exhaust stroke comes into play. This is when the cylinder is full of burnt gas and needs to be pushed out, so, the second valve opens up and the piston moves upwards pushing the gasses out.