Abstract: A method of reducing nitrogen oxide (NOx) emissions of a four-stroke turbo-charged piston engine by injecting water or steam into the combustion chamber of the engine, wherein the water injection is carried out at least substantially during the intake stroke of the engine. The injecting of water is initiated at the earliest when the inlet valve has moved through about 50% of the total range of its opening movement.

Abstract: An injection arrangement for an internal combustion engine, especially a diesel engine, for injecting different pressure mediums directly into a cylinder of the engine, which arrangement includes a first valve (3), which is arranged to inject fuel, and a second (4) valve, which is arranged to inject an additional medium, by means of which the content of noxious substances resulting from burning of the fuel can be decreased. Said second valve (4) comprises an elongated valve member (5) movable within a valve body (2) against the force of a spring (12) and in association with the part of which located on the cylinder side there is arranged a chamber (6), which encircles the valve member (5) and into which said additional medium is arranged to be fed continuously under pressure.