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The First Law of Thermodynamics has been applied to the analysis of the dynamometer performance of a 2.0 litre,115 PS, common rail, turbocharged, automotive diesel engine operating under steady state conditions. Validation of the method is presented with correlation between the input fuel power and summed loss terms shown to be better than 3%. The study was conducted over a matrix of engine speed-load sites and maps of the underlying trends and magnitudes are presented. Detailed analysis of the relative heat balance contributions at a range of loads at fixed engine, water pump, and oil pump speeds is also presented. The proportions of heat rejected to the different primary paths (i.e. brake, coolant, oil, charge cooler, exhaust, and external) were found to vary with engine speed and load. Also, friction power was found to vary principally as a function of engine speed with some small dependency on engine load.

This paper questions whether the application of steady speed volumetric efficiency data to transient SI engine operation under WOT is a valid one. A state-of-the-art computer simulation model is used to compare steady speed volumetric efficiency with instantaneous values. A baseline engine model is first correlated with measured volumetric efficiency data to establish confidence in the engine model's predictions. A derivative of the baseline model, complete with variable geometry inlet manifold, is then subjected to a transient excursion simulating typical, in-service, maximum rates of engine speed change. Instantaneous volumetric efficiency, calculated over discrete engine cycles forming the sequence, is then compared with its steady speed counterpart at the corresponding speed. It is shown that the engine volumetric efficiency responds almost quasi-steadily under transient operation thus justifying the assumption of correlation between steady speed and transient data.