Low Speed Running Characteristics of a Small Two-Stroke Engine with Auxiliary Exhaust Ports

Use of the two-stroke principle is favored in many small, lightweight engine applications. However, in its simplest form the two-stroke exhibits high specific fuel consumption and hydrocarbon emissions, and poor low speed, light load running quality. The need to resolve these problems and produce an environmentally friendly two-stroke engine has led to a variety of research and development efforts. At Michigan Technological University a marine-based two-stroke engine cylinder was reconfigured, with the objective of mitigating the low speed, light load problem. The cylinder utilizes auxiliary low speed ports which, when activated, are designed to reduce the trapped cylinder volume, and provide a higher purity trapped charge prior to combustion. Test results are reported for both intake and direct injection fuel delivery systems, and show that the reconfigured cylinder has improved low speed running characteristics. It is suggested that with further development the low speed port concept could be incorporated as part of an alternative cost effective low emissions solution.