Browse Publications Technical Papers 2018-32-0024

The Effect of Organic Friction Modifiers on Fully Formulated Motorcycle Engine Oils 2018-32-0024

Most high-performance motorcycles use a multiplate, lubricated (“wet”) clutch pack. The main reasons for the lubrication are; cooling, and to protect the steel and friction plates from excessive wear. In such a motorcycle a single common oil sump is usually used to lubricate the engine, clutch and transmission. From a lubricant design point of view the ideal case would be to have individual fluids that are specifically designed for each task, as is the case in the majority of passenger cars. However, in most cases the extra size and weight that would be added by having separate oil sumps rather than one common oil sump is undesirable and would impact the ride and fuel economy. A motorcycle engine oil (MCO) must therefore perform well in several, seemingly contradictory, environments. This makes the choice of friction modifier (FM) more complex than it would be for a passenger car engine oil (PCEO). It is often the case that if a FM reduces friction in a steel/steel contact it will also reduce friction in a steel/friction material contact. Therefore, it is usually viewed that there will be a necessary compromise between maximizing engine efficiency and maintaining efficient clutch performance. In this paper we examine the effect of a range of organic friction modifiers on commercial fully formulated MCOs using benchtop tribotests and full-scale rig tests (SAE #2 clutch test machine). The results show that by careful selection of appropriate FM chemistry it is possible to reduce steel/steel friction whilst maintaining clutch performance.


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