Role of Scavenging in Improving Irregular Combustion and Misfiring in Small Two Stroke Engines

The role of transfer port geometry in improving scavenging near the spark plug with consequent improvement in cyclic variations and irregular combustion have been studied through engine tests by recording the pressure-time data of many cycles with the original and modified ports on a 150cc crankcase compressed shnurle loop scavenged two stroke engine under various operating conditions. The results show that there is an optimum upsweep angle which gives reduction in cyclic variations and lowering of delivery ratio at which irregular combustion starts. The side sweep angle does not seem to affect much. The improvement seems to be closely related to the reduction in the duration of the initial phase of combustion and its variations.