Schnuerle porting

Schnuerle porting[1][2] is a system to improve efficiency of a valveless two-stroke engine by giving better scavenging.

Apart from large diesels with separate superchargers, two-stroke engines are generally piston-ported and use their crankcase beneath the piston for compression.

This "cross scavenging" performs poorly, as there is tendency for the flow to pass from the inlet directly to the exhaust, wasting some of the fuel mixture and also poorly scavenging the upper part of the chamber.

In 1926, the German engineer Adolf Schnürle developed the system of ports that bears his name.

Adolf Schnürle was a prolific engineer and is named on many patent documents.