Counterbalanced throttle for I.C. engine

In a fuel supply means for an automobile engine, an inlet induction passage, a fuel supply port opening into said passage, said passage having an upstream inlet for receiving air and a downstream outlet for discharging a fuel-air mixture, throttle means in said passage downstream of said fuel supply port for controlling the axial flow of said mixture in said passage comprising a pair of throttle members movable axially of said passage and dimensioned to effect a variable restriction for said passage upon simultaneous movement of said members in axially opposite directions, said variable restriction comprising a variable geometry flow diffuser for conducting said flow therethrough at nearly sonic velocity at its region of minimum cross sectional area throughout the major operating range of said engine, and means for essentially balancing the force required to move either member in one axial direction against said flow by simultaneously moving the other member axially with said flow throughout the movement of said members.