Abstract: A water induction system for internal combustion engines which is comprised of a metering device for metering controlled amounts of air and water, a reverse needle vacuum control valve which is operated in response to intake manifold vacuum and is connected to the metering device, and a heater wherein the air-water mixture is vaporized. The manifold vacuum regulated reverse needle control valve allows an increasing amount of air and water to be drawn into the heater as manifold vacuum pressures drop, engine load increases and the engine requires more vapor. At lower loads, the valve operates to cut back the air-water flow into the engine.