Injection control method

The method involves realizing a simple engine operating cycle comprising a main fuel injection step (PRINC) and not having a post-injection step (POST). A combined engine operating cycle comprising both the main fuel injection step and the post-injection step is realized. Total amount of fuel injected during post-injection step is reduced during determined fuel injection duration (Tinj) based on the theoretical fuel amount determined by a theoretical engine operating cycle associated with a theoretical fuel injection duration (TPOSTH).