Driveability Evaluation of Two-Stroke Engine at Part Throttle Operation by Torque Map

With a view to improving the driveability of two-stroke SI motorcycle engines in the region of partial load running over off road surfaces, the quantitative expression of which has generally been difficult, an attempt was made to derive a simple evaluation by using the engine torque map.

Three engines of different specifications to give different control characteristics and torque maps were produced. The identification of passage curves on the torque maps by means of frequency distribution during the running of actual motorcycles has revealed the presence of correlation between the range of the torque fluctuation on passage curves and the evaluated value of driveability.

This made a simple quantitative evaluation of driveability possible without conducting actual running tests. It has been shown that, in the provided engines, nearly satisfactory driveability can be obtained when the range of torque fluctuation is less than about, 100Nm*.