A method of igniting gaseous fuel directly introduced into a combustion chamber of an internal combustion engine comprising the following steps of: injecting, through a pilot injection passageway in a fuel injector nozzle, a pilot amount of gaseous fuel into the combustion chamber during a first stage injection event, igniting the pilot amount of gaseous fuel, injecting, through a main injection passageway in said fuel injector nozzle, a main amount of gaseous fuel into the combustion chamber during a second stage injection event, using heat from combustion of said pilot amount of gaseous fuel to ignite said main amount of gaseous fuel, wherein the pilot injection passageway comprises a pilot cross-sectional area perpendicular to gaseous fuel flow therethrough and the main injection passageway comprises a main cross-sectional area perpendicular to gaseous fuel flow therethrough, characterized in that the method further comprises the following steps: - heating a space around a fuel injector nozzle, - controlling gaseous fuel flow into the combustion chamber between said main amount of gaseous fuel and said pilot amount of gaseous fuel by providing a ratio between the main cross-sectional area of said main injection passageway and the pilot cross-sectional area of said pilot injection passageway within a range of 4 to 49, - wherein the pilot amount of gaseous fuel is introduced into the combustion chamber in a plurality of pilot fuel jets angularly spaced equally around the fuel injector nozzle within a predetermined range of tolerance. injecting, through a pilot injection passageway in a fuel injector nozzle, a pilot amount of gaseous fuel into the combustion chamber during a first stage injection event, igniting the pilot amount of gaseous fuel, injecting, through a main injection passageway in said fuel injector nozzle, a main amount of gaseous fuel into the combustion chamber during a second stage injection event, using heat from combustion of said pilot amount of gaseous fuel to ignite said main amount of gaseous fuel, wherein the pilot injection passageway comprises a pilot cross-sectional area perpendicular to gaseous fuel flow therethrough and the main injection passageway comprises a main cross-sectional area perpendicular to gaseous fuel flow therethrough, characterized in that the method further comprises the following steps: - heating a space around a fuel injector nozzle, - controlling gaseous fuel flow into the combustion chamber between said main amount of gaseous fuel and said pilot amount of gaseous fuel by providing a ratio between the main cross-sectional area of said main injection passageway and the pilot cross-sectional area of said pilot injection passageway within a range of 4 to 49, - wherein the pilot amount of gaseous fuel is introduced into the combustion chamber in a plurality of pilot fuel jets angularly spaced equally around the fuel injector nozzle within a predetermined range of tolerance. - heating a space around a fuel injector nozzle, - controlling gaseous fuel flow into the combustion chamber between said main amount of gaseous fuel and said pilot amount of gaseous fuel by providing a ratio between the main cross-sectional area of said main injection passageway and the pilot cross-sectional area of said pilot injection passageway within a range of 4 to 49, - wherein the pilot amount of gaseous fuel is introduced into the combustion chamber in a plurality of pilot fuel jets angularly spaced equally around the fuel injector nozzle within a predetermined range of tolerance.