Fuel injection strategy for internal combustion engine having dedicated EGR cylinders

A method using exhaust gas recirculation (EGR) in a spark—ignited internal combustion engine having a number of cylinders, each cylinder operable to undergo a series of main combustion events when provided with fuel and air, comprising:

• using one or more of the cylinders as a dedicated EGR cylinder, such that all of the exhaust produced by that cylinder is recirculated to the cylinders;
• using the remaining cylinders as main cylinders, operable to provide power to an engine crankshaft;
• operating the main cylinders at a stoichiometric air-fuel ratio;
• operating the dedicated EGR cylinder at a rich air-fuel ratio;
• and
• using a fuel injector to inject fuel into the combustion chamber of the dedicated EGR cylinder after initiation of the main combustion events, thereby increasing the amounts of hydrogen (H2) and carbon monoxide (CO) in the exhaust gas of the dedicated EGR cylinder.