What is under piston scavenging?

Under piston scavenging is a method used in two-stroke engines to enhance the efficiency of exhaust gas removal and air-fuel mixture intake. In this system, the piston itself creates a vacuum during its downward movement, which helps draw in fresh air-fuel mixture from the crankcase and expel exhaust gases. This technique allows for better filling of the combustion chamber, improving engine performance and reducing emissions. It is commonly found in lightweight two-stroke engines, such as those used in chainsaws and motorcycles.