Looking at the previous pages, you can clearly see all three of the four strokes are either to prepare for or clean up after the Power Stroke.
The Power Stroke is what makes the car move forward.
All the pistons in an engine are connected to same crankshaft. This crankshaft is connected to the transmission which
delivers the power to the tires, which is beyond the scope of this discussion.
Since we are converting up and down motion to circular motion, each stroke takes up 180 of crankshaft rotation. Therefore,
each piston requres 720 degrees of crankshaft rotation for all four-strokes to complete.
To achieve the necessary power that a car needs, engineers design engines with multiple cylinders. They they configure the cylinders
to be in their Power Strokes at differing times. This technique allows the Power Stroke to occur with less degress of separation between
them.
Generally you can determine the number of degress between a power stroke with the following equation:
How Often A Power Stroke Occurs = 720 / number of cylinders
Note: 720 is used since one cylinder needs 720 degress of rotation for the complete four strokes to complete.
Intake (180 degrees) + Compression (180 degrees) + Power (180 degrees) + Exhaust (180 degrees)
For example, a four cylinder engine has a Power Stroke every 180 degress; 720 / 4
Whereas, a eight cylinder engine has a Power Stroke 90 degrees; 720 / 8
Lastly, since we know that a Power Stroke takes 180 degrees, it can be seen why many performance engines tend to be over five cylinders.
Why? Those engine configurations have their Power Strokes overlapping.
