By the systematic variation of the combustion process, the following important influences could be determined: Highest efficiency is reached with a position of the center of gravity near the TDC, low calorific value of the fuel/air mixture and the necessary combustion procedure. The time of combustion itself has no direct influence. Low emissions require a retarded position of the center of gravity. The time of combustion itself has likewise no direct influence. Smooth engine operation can be obtained with a short time of combustion. The noise emission, however, is negatively influenced by it. The selection of the "correct" combustion procedure depends partly on the priorities of the target values.