ECONOMY FROM THE TRUCK DIESEL ENGINE

This article is concerned with the fuel consumption of the medium and large sized four-stroke truck diesel engine, through the study of the various factors which affect the fuel energy conversion within the unit. These factors are classified under two basic headings namely combustion effects and mechanical efficiency. The former group comprises the fuel/air ratio, injection and combustion timing. It is stressed that operating conditions may demand settings of these systems above or below that required for optimum efficiency, and that any mismatching of fuel injection characteristics and air motion can produce significantly worse results. The mechanical efficiency is examined by making measurements of frictional losses with the engine in various stages of assembly. It is shown that losses in the running gear including auxilliaries amount to half of the total at full engine speed, whilst the largest single item contributing to friction loss is the cylinder head, it being responsible for mechanical losses in the valve train, pumping losses and compression losses. /TRRL/