What is the key difference between two-stroke and four-stroke engines?

The key difference between two-stroke and four-stroke engines lies in the number of strokes required to complete a power cycle. In a two-stroke engine, the entire power cycle, which includes intake, compression, power, and exhaust, is completed in just two strokes of the piston (one full revolution of the crankshaft). This means that a two-stroke engine can fire once every revolution of the crankshaft, allowing for a higher power output relative to its size.

In contrast, a four-stroke engine requires four distinct strokes (intake, compression, power, and exhaust) to complete a power cycle, which takes two revolutions of the crankshaft. This results in a power stroke occurring only once every two revolutions, leading to a lower power-to-weight ratio compared to a two-stroke engine.

Understanding this distinction is crucial for grasping the operational characteristics of these engines, including their efficiency, power delivery, and application in various scenarios.