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On the Characteristics of Fuel Injection Equipment of Direct-Injection Diesel Engine Influencing Vehicle Driveability
Published January 01, 1980 by Verlag Des Verein Deutscher Ingenieure GmbH in Germany
Today, the control of emission and economy of fuel are the most important subjects for automotive engines. A higher injection rate in the fuel system is frequently adopted for the diesel engine in order to obtain better fuel economy with a lower exhaust emission level.
However, in the jerk-pump system, the higher injection rate induces poor driveability of the vehicle which includes rough idling, surge, hesitation and stumble. Among these factors, the surge which is a cyclic acceleration change due to fore and aft oscillation of the vehicle is considered to be caused by influence of the engine torque variation, the fuel control system (governor) and the dynamic characteristics of powerline.
Though S. Suzuki has already introduced these phenomena mostly with regard to the fuel injection pump system, in this paper the authors have tried to analyse these phenomena in connection with the vehicle and engine behavior. Namely, the regions of surge and unstable injection both for the vehicle and the engine have been clarified, and the relation between surge and torque fluctuation due to combustion fluctuation by an unstable fuel injection has been found. The behavior of bubbles in the injection pipeline during the unstable injection period was also observed by high speed photography.
Finally, the authors have given some suggestions with actual examples for improvement of the surge by modification of the injection system.