Reduction of Friction Loss through the Use of Rolling Big-End Bearings

We compared motoring friction loss, output performance at WOT (wide open throttle) and specific fuel consumption of big-end bearings on engines having identical specifications between the case of using plain bearings and rolling bearings to investigate the effect of the lubricating oil supply rate on these parameters in an attempt to improve output through reduction of friction loss for big-end bearings of small, high-output motorcycle engines. Testing was performed using a 125 cc, 4-cycle, single cylinder engine at high engine speeds mainly above 10,000 rpm. As a result, it was found that rolling bearings have a lesser effect on lubricating oil supply and crank pin temperature than plain bearings, that friction loss, output performance and specific fuel consumption of plain bearings and rolling bearings are roughly equal in the case of equal lubricating oil supply rate, and that since it is possible to reduce lubricating oil supply rate without an accompanying increase in crank pin temperature in the case of rolling bearings, the benefits of improved output performance and specific fuel consumption resulting from reducing lubricating oil supply rate can be realized to a greater extent than in the case of plain bearings, and the extent of that improvement is roughly 3% for both output performance and specific fuel consumption.