Car Engine Explained:

The Engine Explained

 by: Kevin Schappell

The engine is the heart of your car, but instead of pumping blood, the engine pumps air and fuel. The engines main function is to convert air and fuel into rotary motion so it can drive the wheels of the car. How does it do that ??.... Well let's start with a cutaway of the engine and see all the major parts then we will get into the actual mechanics. p>

Pistons: Most common engines have 4, 6, or 8 pistons, which move up and down in the cylinders. On the upper side of the piston is what is called the combustion chamber where the fuel and air mix before ignited. On the other side is the crankcase, which is full of oil. Pistons have rings which serve to keep the oil out of the combustion chamber and the fuel and air out of the oil.

Crankshaft: The crankshaft is connected to the pistons via a connecting rod. As the piston moves up and down in the cylinder it rotates the crankshaft and converts the straight line motion into rotary motion.

Valve train: The valve train consists of valves, rocker arms, pushrods, lifters, and the camshaft. (shown in above picture in blue, yellow, and green) The valve train’s only job is that of a traffic cop. It lets air and fuel in and out of the engine at the proper time. The timing is controlled by the camshaft, which is synchronized to the crankshaft by a chain or belt.   

Now that we have a general overview of the parts involved let's talk about what happens. Most automotive engine today are 4-stroke (or 4-cycle) engines, meaning they have four distinct events which make up the cycle.

• Intake stroke: The camshaft opens the intake valve and the piston moves down the cylinder. This creates vacuum and sucks in air and fuel into the combustion chamber above the piston.
• Compression stroke: As the piston starts moving back up the cylinder the intake valve closes and seals off the combustion chamber. The causes the air and fuel to compress.
• Power stroke: As the fuel is compressed and the piston nears the top of the cylinder the spark plug fires and ignites the fuel and air. This explosion pushes the piston back down the cylinder and drives the crankshaft.
• Exhaust stroke: After the piston reaches the bottom of the cylinder, the exhaust valve opens and the gasses left over from the fuel and air are sent out to the exhaust system.