Method of controlling a direct-injection gaseous-fuelled internal combustion engine system with a selective catalytic reduction converter

Abstract

A method controls a direct-injection gaseous-fuelled internal combustion engine system to improve the conversion efficiency of an SCR converter that is operative to reduce levels of NOx. The method comprises detecting when the internal combustion engine is idling and timing the injection of a first quantity of fuel to begin injection when the engine's piston is near top dead center; and controlling the temperature of exhaust gas to be above a predetermined temperature that is defined by an operating temperature range that achieves a desired conversion efficiency for the selective catalytic reduction converter, by: (a) timing injection of the gaseous fuel to begin after timing for injection the first quantity of fuel, and (b) increasing exhaust gas temperature by increasing a delay in timing for injecting the gaseous fuel, while limiting the delay to keep concentration of unburned fuel exiting the combustion chamber below a predetermined concentration.