I built a 4 cell hydrogen booster like the one in the pictures. I mounted this cell behind the front bumper of a friends 1997 Ford Escort. The engine was a good running four cylinder and we hooked up a PWM and oxygen sensor simulator and also a MAF Modification to run the cell on his car. A PWM is a pulse width modulator, and electronic control for controlling the current going to cell as in our case, or an electric motor.
The cell had an electrolyte solution that would let it pull 21 amps if it was running straight battery voltage. We ran it at 12 amps when hot with the controls of the PWM holding it at this setting. The electrolyte was water and sodium hydroxide mixture. 6 table spoons to 1 gallon of water which gave us a draw of 21 amps.
After testing and tweaking everything he made a trip of about 1000 miles and his mile per gallon increased from 34 to 38. Not bad for the little four cell. He lives in Iowa and can't run it in the winter because of the freezing but it helps all summer long. We are going to experiment some more with it and see if we can increase his miles per gallon a little more.
If you would like to build one like this then visit my website to see how I made it. I have some pictures of it while I was assembling it and how it was mounted in his car. they are simple to build and could save a bundle over the long run in gas savings.