Abstract: Apparatus and method for modifying existing internal combustion engines that fail to meet current air quality standards so as to bring such engines into compliance. The invention includes the provision of an injection valve assembly for the engine's cylinders that promotes mixing of injected fuel with air present in the cylinder by establishing a cyclonic jetting action in the fuel upon its introduction into the cylinder. The assembly includes a piston and cartridge that are configured for reciprocating engagement, one with the other. The cartridge has channels that impart a rotational spin on pressured gas as it is directed out of the assembly. At least two fuel distribution patterns are created; one that is focused, much like a beam and another that is flared into a conical pattern.