A review of internal combustion engine losses - Part 2: studies for global evaluations

The global evaluation of losses is important in providing information about the behaviour of an engine. This may be used, for instance, in design and development of new models, where one with inherently the lowest friction may be chosen with a consequent potential gain in fuel economy. This paper reviews studies on the determination of total engine losses. Experimental works are reported from which, sometimes with theoretical support, empirical formulae are obtained that allow an extension of the results to engines similar to those investigated. Besides formulae in which losses are expressed as an equivalent pressure averaged in the complete cycle, more detailed formulae for the determination of instantaneous loss torques are reported, which are also useful in obtaining a better evaluation of the engine speed trend in fault diagnosis. All formulae can be used in computer programs for the numerical simulation of engine performance, a use that can reduce the time needed for experimental work.