It really is'nt a topic thats easy to discuss because its far more complicated than the figures imply. The actual time span available is not linked to the inlet valve open time, and neither is the engine air consumption linked specifically to the inlet valve open time.

However one fact that remains categorically is that we have 720degrees ABSOLUTE in every cycle of a 4 stroke engine to actually flow fuel from the injector.

As such the critical parameters are time available for 720degrees crank rotation at the point of peak bhp. From this we can determine what size injector we would use based on 100% duty cyle and then scale from this to use an injector size capable of less than 85%.