Abstract: The uniform distribution and experimental design (U-D design) experiments are made on a small D.I.(Direct injection) diesel engine consisting of the shallow W combustion system. The table of U-D design carries out the experiments on the combus-tion system parameters such as combustion chamber diameters, nozzle hole diameters and nozzle reach, which have influence on the engine’s performances. The better matching schemes are given by the regression analysis. The single factor experiments display that the combustion chamber has important function on engine’s performances. Thinking of the interactive effects, the parameters of nozzle hole and nozzle reach are selected with the combustion chamber. At last, the excellent performances of shallow W combustion system and the valuable conclusions are obtained. It also shows that the U-D design finds out the im-manent rules of experiments. The U-D design is an excellent method to arrange multiple levels’ experiments.

Key words: Shallow W combustion system D.I. (Direct injection) diesel engine, U-D design, Ball bearings, Creepage theory, Friction torque, Rolling contact