Model Engine Company of America
The Basics - 2 Stroke Principal
A two stroke engine must transfer the fuel charge from the crankcase into the cylinder. As the piston moves downward and the intake port on the crankshaft closes (see crankshaft rotation) the fuel charge is compressed. This fuel charge must be directed into the cylinder and accomplish several things. The attempt is to have the have the cleanest fuel/air charge for the next combustion. The remaining exhaust gases from the previous combustion must be pushed out the exhaust port by the incoming fuel/air charge. A clean sweep of the entire cylinder volume is attempted without any of this new fuel charge to escaping out the exhaust port.Port timing and direction are used to accomplish this.
 
ALL THE DIFFERENT PORTING
Schnuerle Porting and the boost port
Named for its inventor, Dr. Schnuerle, these ports are two angled ports that focus the incoming fuel charge towards the back of the cylinder. A Schnuerle ported engine only has to have the two ports to be considered Schnuerle Ported. The boost port, the single angled upward third port, is not a Schnuerle port. It is an additional port to force the fuel charge upward into the cylinder.
   
   
Loop Scavenged. This the the original 2 stroke porting.
 
  PDP - Perry Directional Ports
   
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