Translations:AY Honors/Small Engines/Answer Key/30/en
From Pathfinder Wiki
The four-cycle engine is easier to understand, so it is presented here first. Once the four-cycle engine is understood, it is easier to understand the two-cycle engine.
Four-cycle Engine
A four-cycle engine is so named because it makes four strokes to generate power. These strokes are as follows:
- Intake Stroke: During this stroke the piston moves down in the cylinder, which creates vacuum, drawing air through the carburetor, and sending the mixture of fuel and air into the cylinder. The fuel and air enters through the intake valve which opens at the beginning of this stroke.
- Compression Stroke: Once the fuel and air have been drawn into the cylinder, the intake valve closes and the piston returns towards the engine's head. This compresses the fuel.
- Power Stroke: When the piston reaches the top of the cylinder (just before Top Dead Center or TDC), the spark plug fires, igniting the compressed fuel and air mixture and causing an explosion. This explosion causes the gases to expand which powers the piston downwards again. This is where the engine's power comes from.
- Exhaust Stroke: When the piston reaches the bottom of the cylinder, the exhaust valve opens, and as the piston returns to the top of the cylinder again, the exhaust gases are pushed out. When the piston reaches the top again, the four cycles are ready to repeat.
