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We review some of the key tribological issues of relevance to motorsport applications. Tribology is the science of friction and wear, and in a high performance engine, friction and wear are controlled by good component design (e.g. the engine and the transmission) and also by the use of high performance lubricants with the correct physical (and chemical) properties, matched to the machine they are used in. In other words, design of a specific lubricant for specific hardware can lead to optimised performance. (Tribology is also important in the tire-road contact but are not considered here.) The importance of key physical properties of a lubricant is demonstrated with an emphasis on how the choice of the correct lubricant can help to minimize engine friction (and thus increase available power output) whilst protecting against engine wear. Key lubricant parameters discussed in the paper are the viscosity variation of a lubricant with temperature, shear rate and pressure.

Piston rings are faced with a broad range of demands like optimal sealing properties, wear properties and reliability. Even more challenging boundary conditions must be met when latest developments in the fields of direct injection as well as the application of bio fuels. This complex variety of piston ring design requirements leads to the need of a comprehensive simulation model in order to support the development in the early design phase prior to testing. The simulation model must be able to provide classical objectives like friction analysis, wear rate and blow-by. Furthermore, it must include an adequate oil consumption model. The objective of this work is to provide such a simulation model that is embedded in the commercial MBS software ‘FEV Virtual Engine’. The MBS model consists of a cranktrain assembly with a rigid piston that contains flexible piston rings.

Lubricant samples were aged on a SI bench engine that was run using ten different gasoline fuels. For each gasoline tested, the oxidative stability of the lubricant and the extent of engine wear was assessed in terms of a number of different parameters. Surprisingly, it was found that fuels containing higher levels of olefin (whether C8 olefin, or a C5/C6 olefin blend, or a catalytically cracked refinery stream) performed directionally better than a reference gasoline with low levels of aromatics and olefins. Fuels with a higher final boiling point and higher aromatic content, appeared to be associated with enhanced levels of sludge formation than the reference gasoline, but did not give rise to enhanced engine wear.

The attributes of a traction fluid are fundamental to the successful operation of a traction drive transmission. The fluid must lubricate and protect the components against wear and corrosion, whilst simultaneously providing high traction to transmit power efficiently. A selection of commercial and candidate fluids have been assessed with both a bench-test and a novel traction rig. The principal objective has been to achieve a balance between the conflicting requirements of low temperature viscometrics and high temperature traction. Fluid performance is found to vary according to the rig employed underlining the need to test under prevailing conditions. Data from the traction rig is validated against a variator module.