I built a hydrogen generator and need to know what I can do to increase production enough to actually help ?

It can hold a half gallon of water and has over 140'' of nickel wire inside. I think that it just needs more voltage, am currently running it with 12 volts and 20 amps. I already use electrolyte, but just need to know if there is some way to increase production, or if there is a way to increase the voltage input. My car is a 2.0L 4 cyl. with a five speed. Any help would be appreciated. Thanks for your interest.