AY Honors/Small Engines/Answer Key
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< AY Honors | Small EnginesAY Honors/Small Engines/Answer Key /
Describe the design and operation of the two-cycle engine and the four-cycle engine.
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 draws a mixture of fuel and air into the cylinder. The fuel and air enters through an intake valve which opens during this stroke.
- Compression stroke: Once the fuel and air have been drawn into the cylinder, the intake valve close and the piston returns towards the engine's head. This compresses the fuel.
- Power stroke: When the piston reaches the top of the cylinder, 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 engines power (and noise!) 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 clylinder reaches the top again, the four cycles are ready to repeat.
