Development of Air/Oil-Cooled Motorcycle Engine Using Thermal and Fluid Analyses

To achieve power output and cooling performance in motorcycle air-cooled engines equivalent to those in water-cooled engines, an engine utilizing air-flow generated by the moving motorcycle and a new oil-cooling system for an air-cooled engine was studied. The engine temperature distribution was obtained based on a CFD (Computational Fluid Dynamics) analysis of cooling-air/oil behavior using an inline four-cylinder 900cm³ engine. As a result of this study, engine temperature was sufficiently decreased and the difference in temperature among cylinders was reduced; the engine was tested in a prototype motorcycle.