Two-Stroke Engine
In a two-stroke engine, the piston completes one power stroke during each revolution of the crankshaft. This is accomplished by having two strokes of the piston for each complete cycle:
1. Intake and Compression Stroke: The piston moves down the cylinder, drawing in a mixture of fuel and air through the intake port. As the piston moves up, it compresses the fuel-air mixture.
2. Power Stroke and Exhaust Stroke: The spark plug ignites the fuel-air mixture, creating an explosion that drives the piston down the cylinder. As the piston moves down, it also opens the exhaust port, allowing the exhaust gases to escape.
Four-Stroke Engine
In a four-stroke engine, the piston completes one power stroke during every two revolutions of the crankshaft. This is accomplished by having four strokes of the piston for each complete cycle:
1. Intake Stroke: The piston moves down the cylinder, drawing in a mixture of fuel and air through the intake valve.
2. Compression Stroke: The piston moves up the cylinder, compressing the fuel-air mixture.
3. Power Stroke: The spark plug ignites the fuel-air mixture, creating an explosion that drives the piston down the cylinder.
4. Exhaust Stroke: The piston moves up the cylinder, pushing the exhaust gases out through the exhaust valve.
Comparison
The main difference between two-stroke and four-stroke engines is the number of strokes required for each power stroke. Two-stroke engines are more efficient than four-stroke engines, as they produce more power for a given displacement. However, two-stroke engines also produce more emissions and are generally louder than four-stroke engines.
In general, two-stroke engines are used in small engines, such as those found in chainsaws, weed trimmers, and motorcycles. Four-stroke engines are used in larger engines, such as those found in cars, trucks, and airplanes.
