We developed the numerical simulation tool by using OpenFOAM® and in-house simulation codes for Gasoline Direct Injection (GDI) engine in order to carry out the precise investigation of the throughout process from the internal nozzle flow to the fuel/air mixture in engines. For the piston/valve motions, a mapping approach is employed and implemented in this study. In the meantime, the spray atomization including the liquid-columnbreakup region and the secondary-breakup region are simulated by combining the different numerical approaches applied to each region. By connecting the result of liquid-column-breakup simulation to the secondary-breakup simulation, the regions which have different physical phenomena with different length scales are seamlessly jointed; i.e., the velocity and position of droplets predicted by the liquid-column-breakup simulation is used in the secondary breakup simulation so that the initial velocity and position of droplets are transferred. The simulation technique above is verified as the follows. Firstly, the air-flow simulation for engines is compared to the experiments. The simulation results agree will with the experiment in terms of the velocity profile and the turbulence velocity profile. Secondary, the spray shape and the penetration are quantitatively compared to the experiments. It is observed that the simulation results agree well with the experiment. Finally, the spray simulation is implemented in engines with piston/valve motions. The fuel/air mixture during the aspiration process can be predicted.