A direct-injection internal combustion engine has a rotationally symmetric combustion chamber which is located in the crown of a piston. Air for combustion is admitted into the combustion chamber in such a manner as to circulate about the axis of the latter. Fuel is injected into the combustion chamber through a discharge passage as a function of the engine load and speed. Within the upper range of engine load and speed, the fuel is injected as a concentrated jet and virtually all of the fuel is deposited upon the wall of the combustion chamber. The fuel evaporates from the wall and then mixes with the circulating air. In the lower range of engine load and speed, as well as during idling, the fuel is injected in the form of a finely atomized jet and mixes with the circulating air directly. The effective cross-sectional area of the fuel discharge passage in the lower range of engine load and speed is maintained between about 3 and 15% of the effective cross-sectional area at maximum output. Furthermore, the maximum injection pressure at the discharge passage at nominal rating is maintained at a value approximately 2 to 3 times greater than the pressure required to open the discharge passage.
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