A flow control system for use in a compressible fluid-fueled internal combustion engine includes a fluid metering device comprising a plurality of fluid lines for communication between an inlet fluid manifold and a metered fluid manifold. Bistable valves of various orifice sizes are provided, one in each of the fluid lines except for at least two lines, which are provided with pulsing valves. The device also includes sensors for determining parameters of the inlet fluid sufficient to determine potential mass flow of fluid through each of the valves, and valve controls for activating valve actuators to open the valves in combinations and for time intervals to give a desired total mass flow of fluid through the valves. The total fluid flow passing from the metering device comprises a base flow component established by opening selected bi-stable control valves to provide a continuous predetermined flow, discrete step changes in the base flow component being provided by opening and closing combinations of bi-stable control valves. Increments of fluid flow between the discrete steps are provided by opening at least one pulsing valve for a fraction of a predetermined time period to provide a desired average flow over the time period.