A method for providing adaptive control of the flow of a plurality of ejector valves arranged in close proximity to each other in a sorting machine is described. The method comprises measuring a temporal response curve for each ejector valve, comparing the measured temporal response curve for each ejector valve to a library set of previously stored temporal response curves, determining from the comparison a predicted flow for each ejector valve, and adapting a drive signal for each ejector valve in dependence on the predicted flow. Temporal response curves may be measured and compared in a calibration (non-sorting) mode, and real-time feedback of the measured temporal responses in a sorting mode may be used to indicate health of a valve and to further adapt the drive signal to provide conformal performance. The number of neighboring ejector valves may also be taken into account.