- A car engine starts and functions by the use of a tiny spark. This spark ignites the gas that causes a tiny explosion which pushes a piston that turns a crank shaft. There is a lot more that happens during this time, however. The piston actually has three jobs--to compress the gas and air, to receive the power of the explosion, and transfer that energy to the crankshaft. Keep in mind that there are several pistons connected to one crank shaft, and all of them are rotating at intervals. When one is going up, the other is coming down.
Pistons and Crankshaft
- The engine piston is located inside a cylinder where the explosion takes place. This piston is connected to the crankshaft, and as the piston moves up and down in the cylinder, it turns the crankshaft which gives drive power to the car. To begin, we will imagine the cylinder is compressed, filled with gas and air. A spark fires, pushing the piston to the bottom of the cylinder, and turning the crank shaft one half revolution.
Exhaust and Gas Valves
- Now the cylinder is filled with exhaust from the explosion. A valve opens at the top of the cylinder, and as the piston is pushed back up the cylinder (by the turning crankshaft driven by another piston firing), the exhaust is expelled from this open valve. Since that piston is now pushed to the top of the cylinder, all the exhaust is pushed out of the engine. As the crankshaft continues to turn, the piston is brought back down in the cylinder. Another valve on the other side of the cylinder opens and a gas and air mixture fills the cylinder. On the next rotation, the piston is pushed back up into the cylinder compressing the mixture. The spark fires and propels the piston back down again.
Starting the Car Engine
- When the car is turned on, gas is injected into the cylinder with air. The crankshaft is turned manually to compress the air and gas. The spark plug fires and ignites the air-gas mixture causing a contained explosion which propels the piston back down, turning the crank shaft halfway around. This starts the entire process. Remember, when one piston is being forced up the cylinder, another is being forced down in the cylinder, this keeps the crankshaft moving and the engine running.