To investigate the relation of NOx emission and consumption rate in a direct injection diesel engine with a multihole nozzle under same fuel consumption and rpm, a naphthyl ethylenediaming method on NO, emission and Tektronix oscilloscop on the indicator diagrams have been used. Comparisons of the NOx emission and fuel consumption rate made on various conditions have led to the fllowing results. 1. The higher the injection pressure in the later injection time the lower NOx emission and the fuel consumption rate have been attained. 2. By the change of nozzle hole diameter under the same injection pressure, the NOx emission was much more lowered in the small diameter than large one, but fuel consumption rate was in inverse proption to the NOx emission. 3. The effect of injection spray angle, 1ndn on NOx emission, fuel consumption rate under same injection time and injection pressure was neglectable.

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