A method of calculation is proposed that allows, on the basis of cause-and-sequence approach, to improve the main quantitative characteristics of diesel engines by means of optimization of fuel injection conditions and finding out parameters of fuel injection equipment (TA) for their realization. When using the method, it is assumed that certain technical requirements and limits are to be observed (for instance, the maximum combustion pressure, engine noise, emission standards etc.). The two stages of the method are reflecting the natural sequence of TA design.Components of a developed mathematical model are described in this paper. In particular, special attention is paid to an original phenomenological model of a dispersed fuel spray on the basis of experimental data pertaining to its structure and mixture formation mechanism.This method has already shown its effectiveness for different practical tasks of minimizing fuel consumption of a diesel engine with known design and setting parameters. Some results are given of real calculations for diesel engines with different dimensions and supercharging rate.