Patent ID: 7013861

Claim:
A method of operating a self igniting internal combustion piston engine, comprising: injecting fuel directly into an engine combustion chamber in a plurality of fuel jets of a certain range utilizing an injection nozzle having a nozzle needle and injection holes, said injecting including a plurality of sequential clocked pre-injections at respective pre-injection pressures followed by a main injection at a higher injection pressure than the pre-injection pressures, wherein the clocked pre-injections are controlled so that the injected fuel jets have a range smaller than a distance to a boundary of the combustion chamber, and wherein the combustion chamber is bounded by a cylinder and a piston, said injection nozzle being disposed in a region of a cylinder central axis and said piston including a piston head which in use faces the injection nozzle and includes a piston recess with an approximately centrally disposed recess projection.