The Relationship Between Port Shape and Engine Performance for Two-Stroke Engines

Measurement using a three-dimensional anemometric-tester was made for the gas flow inside the cylinder of a two-stroke engine while the shape of the transfer port was modified. The relationship between port shape and engine performance was investigated for various factors that characterize the flow in cylinder. In this paper, we focused mainly on two engine running conditions: the maximum output at 11750 rpm and the output at 10000 rpm. As a result, we found that the maximum output is most related to the tangential inclination angles of the main transfer port, and the inner vent radius of the main transfer duct.