A hydrogen generation system for producing hydrogen and injecting the hydrogen as a fuel supplement into the air intake of internal combustion engines. Hydrogen and oxygen is produced with a fuel cell at low temperatures and pressure from water in a supply tank. The hydrogen is directed to the air intake of the engine while the oxygen is vented to the atmosphere. The device is powered by the vehicle battery. The system utilizes an engine sensor that permits power to the system only when the engine is in operation.