This invention is a fuel valve used with a nitrous oxide delivery system to control supplemental fuel flow to an engine. This valve is typically a normally closed valve which is opened by application of nitrous oxide under pressure when the nitrous oxide delivery system is activated. This application of nitrous oxide pressure applies an internal force to a piston means whereby the valve is opened and supplemental fuel flows to the engine. Upon de-activation of the nitrous oxide system and subsequent decrease of nitrous oxide pressure, the valve closes and supplemental fuel flow to the engine ceases. This valve is smaller and less costly than electrical solenoid valves presently in common use.