 Work published at SAE in 2012 points that loop scavenging is under every circumstance more efficient than cross-flow scavenging.In a uniflow engine, the mixture, or "charge air" in the case of a diesel, enters at one end of the cylinder controlled by the piston and the exhaust exits at the other end controlled by an exhaust valve or piston.The scavenging gas-flow is therefore in one direction only, hence the name uniflow.