"Hydrogen Generator Cell"

If a car gets 38 miles to the US Gallon, that is about 10 miles per liter.

One liter of gasoline weighs aproximately .75Kg
The Gasoline / Air Ratio is about 1:14.7.
So the volume of vaporized gasoline will be about 15.7 liters

One Liter of gasoline produces about 13 Kwh of energy.
One Kilogram of Hydrogen produces 33.3 Kwh of energy.

So Hydrogen produces (33.3 / 13) 2.56 time more energy than gasoline.
The Hydrogen / Air Ratio is about 1:34.
So the volume of this mixture will be about .293 X 34 = 9.96 Kg 

Now if this same car above is run on hydrogen and you expect to get the
identical horsepower, it will require .75 Kg / 2.56 = .293 Kg of hydrogen
every 10 miles.

Next: 0.09 Kg of Hydrogen = 1 cubic meter of Hydrogen Gas or 1,000 liters.

This means that .292 Kg of hydrogen: .292 / 0.09 = 3.2444 Cubic Meters of
hydrogen or 3.2444 X 1000 = 3,244.4 liters of Gas per 10 miles

Assuming a speed of 60 Miles per Hour, or One Mile per minute, this works out
to Needing to generate (3244.4 / 10) 324.4 Liters of Gaseous Hydrogen
every Minute.