Kaksitahtisella

Kaksitahtisella refers to a two-stroke engine, a type of internal combustion engine characterized by its two-stroke cycle of operation. Unlike a four-stroke engine, which completes its cycle in four piston movements (intake, compression, combustion, exhaust), a two-stroke engine accomplishes these same functions in just two piston movements, or one complete revolution of the crankshaft.

The two-stroke cycle typically involves simultaneous intake and exhaust processes. As the piston moves upwards, it creates a vacuum in the crankcase, drawing the fuel-air mixture into the crankcase through an intake port. Simultaneously, the upward movement also compresses the fuel-air mixture already in the cylinder above the piston. As the piston reaches the top of its stroke, ignition occurs, forcing the piston downwards. As the piston descends, it uncovers the exhaust port, allowing burnt gases to escape. Shortly after, it uncovers the transfer port, allowing the fresh fuel-air mixture from the crankcase to be pushed into the cylinder, simultaneously scavenging (pushing out) the remaining exhaust gases and beginning the next cycle.

This design results in a simpler engine with fewer moving parts, making it lighter and often more powerful for its size compared to a four-stroke engine. However, two-stroke engines typically have less efficient fuel combustion, higher emissions due to unburnt fuel escaping with exhaust, and often require oil to be mixed with the fuel for lubrication, as the crankcase is used for fuel transfer. Common applications for two-stroke engines include smaller motorcycles, mopeds, chainsaws, leaf blowers, and outboard motors.