Simulated fuel dilution and friction-modifier effects on piston ring friction

Government legislation, customer requirement, and pressure from the original equipment manufacturers (OEM) continually pushes the issue of increased vehicle fuel economy to the forefront. Lubricant manufacturers responded by creating low viscosity lubricants with complex additive packages capable of reducing total engine friction while maintaining the useful life of the engine. An important component in the lubricant additive package is the friction modifier, whose job is to reduce the sliding friction of components operating in the boundary lubrication regime. It is widely agreed that 40-60 per cent of mechanical friction can be attributed to the piston/ring/ cylinder wall interface, much of which is as a result of the compression ring whose lubrication is kept purposely minimal to control exhaust emissions. A logical progression to research suggests utilizing fuel to administer friction modifier directly to the top ring zone of the engine, the area where its effects are most beneficial. This article describes a series of tests conducted using a Plint TE-77 reciprocating tribometer to investigate the synergy of lubricant and fuel containing friction modifier at the top ring zone. A computational model has been modified and utilized to further investigate the potential impact of administering friction modifier at the top ring zone via the fuel.