Method for operating an internal combustion engine

A computer-readable medium containing a computer program which when executed by a processor performs the following method for operating an internal combustion engine working according to the Otto principle:

• injecting fuel directly into a combustion chamber for inflaming the fuel by self-ignition;
• ascertaining a characteristic quantity characterizing a stability of combustion of an air/fuel mixture located in the combustion chamber;
• and
• setting, as a function of the characteristic quantity, a residual gas proportion in a cylinder associated with the combustion chamber, the residual gas proportion being reduced as long as the characteristic quantity does not fall below a specifiable stability boundary.

A control unit for operating an internal combustion engine working according to the Otto principle, comprising:

• means for injecting fuel directly into a combustion chamber for inflaming the fuel by self-ignition;
• means for ascertaining a characteristic quantity characterizing a stability of combustion of an air/fuel mixture located in the combustion chamber;
• and
• means for setting, as a function of the characteristic quantity, a residual gas proportion in a cylinder associated with the combustion chamber, the residual gas proportion being reduced as long as the characteristic quantity does not fall below a specifiable stability boundary.