With the advance of computational fluid dynamic methods for simulation of diesel engines, the requirement is felt to find the optimal operational design by scanning through various design points. In this sense, a design of experiment technique was applied to a baseline 1.8L Ford diesel engine by defining a multi-objective function that is consisted of sub-objectives of NOx emission and spray droplet diameter. The success of the optimization procedure is contingent upon reduction of emission and enhancement of the spraying characteristics.It is determined that the effect of adjustment in injection strategy is more important than that of the engine modification. A slight reduction of inner bowl diameter and bowl radius should be concomitant with decrement of spray cone angle and injection angle with respect to the baseline engine. The best design configuration is achieved at Run ID 22 (R4/Di/injection angle/spray cone angle=5.77mm/43.7mm/121.9deg/4.11deg). DoE method using Sobol sequence is used incorporating with the support vector regression to predict output parameters with acceptable accuracy in this research project.