Is Running Your Car With Water By Making Your Own Reactor A Realistic Option? Or Is Water4gas.com A Scam?

water4gas and a few other websites claim they have found the answer on how to run a car with water by making your own small reactor that converts the water into brown gas does this really work without out any other fuel supplement? If it does is there enough energy coming out to run your car and produce enough electric to continue the conversion or is it all a myth?