dwusuwowym

Dwusuwowy is an adjective used in Polish to describe a two-stroke internal combustion engine. Its instrumental form is dwusuwowym, which appears in phrases such as silnikiem dwusuwowym. Two-stroke engines complete the working cycle in two piston strokes per one crankshaft revolution, in contrast to four-stroke engines that require four strokes and two crankshaft revolutions.

In operation, the cylinder contains intake, compression, combustion, and exhaust events that are partially combined in each revolution. The engine typically uses ports in the cylinder wall for intake and exhaust rather than a separate valve train. Mixtures of air and fuel are drawn into the crankcase or directly into the cylinder, then compressed and ignited. Scavenging, the process of clearing exhaust gases, occurs through ports and sometimes additional transfer passages, enabling the fresh mixture to fill the cylinder.

Lubrication distinguishes many dwusuwowe engines from four-stroke designs. Traditional two-stroke engines mix oil with fuel, providing lubrication for moving parts as the mixture circulates through the engine and burns. Some modern designs employ separate oil lubrication or oil-inject systems to reduce emissions and improve reliability.

Advantages of dwusuwowy engines include a simpler construction, lighter weight, fewer moving parts, and a high power-to-weight ratio. Disadvantages are generally higher fuel consumption, greater emissions of unburnt hydrocarbons, more noise, and shorter component life due to lubrication challenges. These engines are common in small portable equipment, chainsaws, outboard motors, and many motorcycles and mopeds, especially where compactness and low cost matter.

Historically, two-stroke designs emerged in the 19th century and gained popularity in a range of lightweight applications, though environmental regulations have led to reduced use in some regions.