Method for operating a compression ignition engine

A method of operating a compression ignition engine, the engine having a cylinder and a piston movable in the cylinder, said method comprising:

• forming a combustible mixture by mixing substantially homogeneously a first fuel and air, and introducing the combustible mixture of the first fuel and air into the cylinder;
• compressing the combustible mixture with the piston in a compression stroke;
• injecting a second fuel into the combustible mixture at an injection-time of the second fuel during the compression stroke but before start of combustion to create a cylinder charge, the second fuel being capable of auto-igniting earlier than the first fuel;
• continuing the compression stroke until combustion starts in the cylinder at locations where at least one of (i) concentration of the second fuel is highest and (ii) temperature of the combustible mixture is the highest;
• monitoring emissions of the cylinder caused by the combustion by differentiating between NOx and HC emissions;
• and
• if said monitoring determines that HC emissions are above a predetermined HC emissions threshold value individually for the cylinder, then performing:
• increasing an amount of the second fuel injected;
• retarding an injection timing of the second fuel;
• and
• increasing a temperature of the cylinder charge.