What is the difference 2 Stroke Engine and 4 Stroke Engine?
How Do Combustion Engines Work, and What Is A “Stroke” Anyways?
- In order to understand how these two engines are different, you first need to become familiar with the basics.
- During an engine’s combustion cycle, the piston moves up and down within the cylinder. The terms “top dead center” (TDC) and “bottom dead center” (BDC) refer to the piston’s position within the cylinder. TDC is its position nearest to the valves, and BDC is its position furthest from them. A stroke is when the piston moves from TDC to BDC, or vice versa. A combustion revolution or combustion cycle is the complete process of gas and air being sucked into the piston, igniting it, and expelling the exhaust:
Intake: The piston moves down the cylinder allowing a mixture of furl and air into the combustion chamber
Compression: The piston moves back up the cylinder; the intake valve is closed to compress the gasses within
Combustion: A spark from the spark plug ignites the gas
Exhaust: The piston goes back up the cylinder and the exhaust valve is opened
Difference Between A 2-Stroke & A 4-Stroke
The Difference between a 2-stroke and a 4-stroke engine is how quickly this combustion cycle process occurs, based on the number of times the piston moves up and down during each cycle.
4-Stroke: In a 4-stroke engine, the piston completes 2-strokes during each revolution: one compression stroke and one exhaust stroke, each being followed by a return stroke. The spark plugs fire only once every other revolution, and power is produced every 4-strokes of the piston. These engines also do not require pre-mixing of fuel and oil, as they have a separate compartment for the oil.
2-Stroke: In a 2-stroke engine, the entire combustion cycle is completed with just one piston stroke: a compression stroke followed by the explosion of the compressed fuel. During the return stroke, the exhaust is let out and a fresh fuel mixture enters the cylinder. The spark plugs fire once every single revolution, and power is produced once every 2-strokes of the piston. Two-stroke engines also require the oil to be pre-mixed in with the fuel.