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With the intention of improving engine performance and emissions, the authors examined the influence of the method of initial fuel injection quantity reduction and of the injector configuration of a common rail fuel injection system on engine performance and exhaust emissions. Results showed that decreasing the nozzle hole diameter was an effective way to reduce the initial injection quantity without increasing black smoke. Compared to a three-way type injector, it was found that a two-way type injector can greatly reduce the amount of fuel leakage from the electromagnetic injector control valve and fuel consumption could be further improved by reduction of the driving loss. Furthermore, the increase of driving losses with higher injection pressure was small, and as a result, higher pressure injection was possible.

Recent global environmental problems which have come to light must be solved for ensuring the survival of the human race. And it is of the utmost importance that we give to our descendants a world full of nature and beauty. In the past years Mitsubishi Motors Corporation (MMC) has long been positive in research and the development activities so as to satisfy the demands for low emission and good fuel economy vehicles. (1) As one example of our research efforts, the technology that will meet the US '94 HDDE exhaust emission regulations, which is one of the most stringent regulations in the world, is described in this paper. The exhaust emissions were reduced by improvement of combustion, using the pre-stroke control type fuel injection pump and optimizing the combustion chamber shape. Efforts were also made to improve the oil consumption, in order to reduce PM (Particulate Matter) emission.

Oil consumption is able to be measured in short time by detecting SO2 concentration in exhaust gas by the “S-trace method” which uses sulfur in lubricating oil as a tracer. Application of this S-trace method to a diesel engine has not been reported yet. Our application of this method to a diesel engine has proved that S-trace method not only can replace the weight method, but also enables measurement of oil consumption in transient operation of an engine, though consideration must be paid to the accumulation of unburned oil. This paper describes the modification of S-trace method so as to be applicable to diesel engines and some examples of oil consumption measurement in transient operation of an engine. In certain conditions of transient operation of an engine, there is a great difference in the oil consumption data between the actual measurement and the estimation from steady state operation.