Totakts

Totakts, in English known as two-stroke engines, refer to a type of internal combustion engine in which a complete power cycle is completed in two strokes of the piston, typically one revolution of the crankshaft. This contrasts with four-stroke engines, where the cycle spans four strokes and two revolutions.

The basic operation combines intake, compression, combustion, and exhaust within a single crankshaft revolution. The cylinder walls contain ports that are uncovered by the moving piston to admit a fresh air–fuel mixture and to vent exhaust gases. In traditional crankcase-scavenged designs, the crankcase itself acts as a temporary reservoir for the incoming charge; in other designs, valves, reeds, or direct fuel injection improve scavenging and reduce losses. The mixture is then compressed on the rise of the piston, ignited, and the resulting power impulse helps expel exhaust gases while drawing in a new charge on the next cycle.

Lubrication for many older two-stroke engines involves premixing oil with fuel or using an oil injection system. This results in higher deposition and smoke and contributes to greater emissions compared with many four-stroke designs. Modern two-stroke developments, including direct fuel injection and advanced scavenging, aim to lower emissions while preserving the high power-to-weight ratio typical of the design.

Applications are common in small motorcycles, chainsaws, lawn and garden equipment, outboard motors, and other lightweight power tools. While still favored for their simplicity and compactness in certain sectors, they face increasing regulatory pressure to reduce emissions, leading to ongoing design innovations and selective phase-outs in some markets.