Abstract: An injection nozzle for injecting a fluid, the injection nozzle including a nozzle body and a nozzle hole defining a flow passage for fluid, the flow passage including passage walls and the nozzle hole having an inlet in fluid communication via the flow passage with an outlet wherein, the inlet is larger than the output and for at least one section through the inlet and outlet along the flow passage that the nozzle hole is defined, for all distances x within a substantial length of the flow passage, by the condition: |(dS/dx)|>45 microns/millimeter, where S=passage wall separation and x is the distance from the inlet.