uniflow two-stroke-cycle engine

A uniflow engine is a type of engine where steam or gas enters through admission valves at the cylinder ends and exits through exhaust ports uncovered by the piston near the end of its stroke. In a uniflow two-stroke gasoline engine, the fresh fuel mixture is forced into the cylinder through ports by a blower. Exhaust gases exit through poppet valves in the cylinder head.12

Opposed-piston engines also utilize uniflow scavenging. These engines have two pistons moving in opposite directions within the same cylinder, eliminating the need for poppet valves. While two-stroke engines can be noisy and polluting, advancements like fuel injection can improve their efficiency and reduce emissions.32