Abstract: A method is shown for operating an internal combustion engine having a combustion chamber with a piston, the internal combustion engine capable of injecting fuel into the combustion chamber multiple times during a cycle, the method comprising: performing a first fuel injection after approximately ?25 crank angle degrees after top dead center and before approximately 15 crank angle degrees after top dead center; and performing a second fuel injection at least 5 degrees after the start of the first fuel injection and less than approximately 25 crank angle degrees after the start of the first fuel injection.

Abstract: A method for operating a diesel IC-engine being able to run in a conventional mode and in a partial Homogeneous Charge Compression Ignition (pHCCI) mode. The method comprises the features of switching the pHCCI mode from lean pHCCI to rich pHCCI as a response to a control signal indicating that the NOx-absorbent shall be regenerated. In the rich pHCCI mode, the ratio of recirculated exhaust gases is from 20 to 55%. The rich pHCCI mode further comprises the feature of injecting at least 70% of the fuel to be injected in each working cycle in the main injection whereby the central axis of the fuel spray is directed towards the piston bowl cavity. The method will increase the operation window for rich pHCCI which in turn will have the benefits of less oil dilution and better fuel economy while regenerating the NOx-absorbent.