Development of a High-Frequency Measurement Apparatus for Evaluating Piston Friction in a Small Gasoline Engines

Efforts to enhance fuel efficiency in small gasoline engines, vital for reducing CO2 emissions, are concentrated on minimizing piston friction losses. Achieving this balance while addressing concerns such as piston seizure prevention and minimizing oil consumption presents challenges, particularly in small gasoline engines operating at higher speeds where the risk of piston seizure is significant. Hence, there is a critical need for accurate methods to measure piston friction. This study introduces the development of a measurement apparatus employing the floating liner method, initially devised by Takiguchi [1] and further adapted by Yamasaka for a mono-cylinder air-cooled gasoline engine [2, 3]. Yamasaka’s research successfully investigated the correlation between the apparatus’s natural frequency and the maximum engine speed measurable, achieving piston friction measurement up to 5000 rpm. Expanding on this achievement, this research aims to broaden the application of the floating liner method to a mono-cylinder water-cooled gasoline engine, enabling precise piston friction measurement up to 6000 rpm. The developed apparatus effectively captured piston friction forces at high engine speeds, offering insights into friction force generation characteristics during each engine stroke. In conclusion, the newly developed measurement apparatus proves to be a valuable tool for piston development aimed at enhancing fuel economy. The findings from this study contribute to ongoing endeavors to improve the efficiency of small water-cooled gasoline engines, thereby reducing their environmental footprint.