The mixture formation and combustion process in direct fuel injection engines was analyzed using the simulation program developed by the authors. The following conclusions were obtained. (1) The swirl air motion generated in the cylinder plays an important rule for carrying fuel vapor around the spark plug. (2) The combustion period becomes shorter due to reduction of attachment of fuel on the piston when using the skewed spray. (3) There is an empirical correlation between homogeneity of the in-cylinder mixture and the engine torque obtained experimentally. (4) Generation of a uniform mixture in the cylinder is important to improve combustion efficiency.