Part of Lesson Plan: **The 4 strokes of an engine (updated) by Curt Erales

Activity Overview / Details

This lesson is designed for entry level students to understand the four strokes of an engine and how a 4 stroke engine functions.

The engines of cars actually have multiple cylinders. The movement of the piston from the top of its travel to the bottom of its travel is called a stroke. Each cycle required to the air-fuel mixture has 4 strokes.

During the intake stroke, the piston is pulled down by the turning of the crankshaft, creating a vacuum above it.

The piston moves back up in the cylinder on the compression stroke, compressiing the air-fuel mixture. As the piston approaches the top of its travel, a spark ignites the mixture.

During the power stroke the burning fuel expands rapidly, forcing the piston to move back down in the cylinder. The exhaust valve opens as the piston approaches the bottom of its travel. This is so that burning gases can escape before the piston begins to move upwards in the cylinder again.

During the exhaust stroke the piston moves back up forcing any remainding exhaust form the cylinder through the open exhaust valve. As the crankshaft rotates, the piston goes back down in the cylinder as the 4 stroke cycle repeats itself.