Abstract: A combustion engine is provided with a fuel supplementation system in which water is broken down by electrolysis into hydrogen and oxygen which are then added to the fuel delivery system. The electrolysis takes place in a chamber in which a pusher gas rises through perforated horizontal electrode plates to sweep the hydrogen and oxygen from the plates as it is generated, thereby preventing the accumulation of these gases in the chamber. In addition, the electrolyte can be circulated, passing it through a filter, to increase the turbulence and agitation within the chamber. The rate at which the water is electrolyzed is varied, as by modulating the voltage applied to the plates, in accordance with the throttle position of the engine. Since gases do not accumulate in the chamber, variations in the rate at which these gases are yielded are affected substantially instantaneously. Lignite activited water can be added to the electrolyte to inhibit the formation of sludge.