understanding a car engine

A basic car’s engine can be broken down into terms that anyone can understand. The goal of an engine is simple, move the car, which is accomplished by turning the wheels. The wheels are connected through the driveline (transmission, rear end gears), which connects to the engine. The rotation comes from a part in the engine called the crankshaft. The crankshaft is connected to a straight “bar” of metal called the connecting rods. On the top of the rods are pistons, cylindrical aluminum pieces that have rings of metal around them. The rings seal them close to the cylinder bore. The cylinder bore is simply a long hole that the pistons can move up and down in. This up and down motion pushes the rods down and rotates the crankshaft. Make sense so far? Next, the piston gets it’s motion from an “explosion” that happens when it is in the top part of the cylinder bore. This makes the piston move downward very quickly. For an “explosion” to occur the engine needs two things, air and fuel. At the top of the cylinder bore, it is sealed, to force the piston down, with a cylinder head. The cylinder head also allows fresh air to come into the cylinder bore and after the “explosion” allows the used air (exhaust) to leave the engine so more fresh air can come in next time.

 

The air and exhaust openings have to be controllable so that the “explosion” can still move the piston. The holes are controlled by valves, which move into the cylinder bore slightly, to move air in or exhaust out. They both close when the “explosion” called combustion happens. The valves are lifted and closed by a round metal rod called a camshaft or cam. The cam has lobes or “lumps” that move the valves up and down as it rotates. The cam is rotated by timing chain or timing belt that runs back to the crankshaft. As the exhaust moves out of the cylinder and travels past the valve it moves through “pipes” called an exhaust manifold or header. From there it moves through the actual exhaust pipes through the catalytic converter, muffler and out the tailpipe. Now the air coming into the cylinder first passes through an air filter. The amount of air being let in is controlled by a rotating plate, turned by your foot stepping on the “gas” petal. The air passes this plate which is part of a carburetor or throttle body. It then passes through tubes called an intake manifold, past the valve and into the cylinder. Some where in this air intake process fuel gets mixed into the air. When this mixture of fuel and air reach the cylinder the valve opens up and sucks the air into the cylinder as the piston moves down. The valves are closed as the piston moves up compressing the air in the cylinder. When the piston reaches the top of the cylinder bore a spark plug, located in the cylinder head sparks. This spark makes the flammable gasoline explode. Then the exhaust valve opens letting out the exhaust. The spark is timed by a device called the distributor. This is a very, very basic explanation of how an engine works. There is a lot more to the full process. I hope this opens the door for new people to learn more about engines on this site.