A controller, in electrical communication with the one or more of the injectors and a high-pressure fuel pump, generates a first signal responsive to which the valve in the injector opens or closes and a second signal responsive to which the high-pressure fuel pump increases or decreases the pressure level in the fuel accumulator. The system may also include one or more sensors for detecting a temperature of air in an air manifold, a pressure within the air manifold and a barometric pressure. The controller is programmed to estimate an in-cylinder gas density using data received from the sensors. The controller accesses a database having data representative of one or predetermined in-cylinder gas densities that are associated with one or more predetermined fuel injection parameters. The controller then generates one or more commands indicative of the fuel injection parameters that are associated with a predetermined in-cylinder gas density.