I have been researching the Economy and Hydrogen world for sometime now. Being a auto mechanic and being not only booksmart but streetsmart, I have decided to try to evade people from throwing away their hard earned cash.
First the Hydrogen deal:
Lets get the facts straight. Water is H2O aka- 2parts Hydrogen, 1part Oxygen combined together. When put under electrolysis or electrosis these molecules split forming a gas known as HHO which is a very explosive and powerful gas. The smallest of sparks can ignite the gas and if stored into container which for some reason caught fire the result could be fatal. No need to get scared though, if the proper precautions are made, no danger is to be seen.
HHO is about 3 times more powerful than gasoline vapor. Meaning 1L of HHO would give your vehicle 300% more power than 1L of gasoline vapor. But feeding an engine pure hho would destroy it due to the fact timing is advanced(spark before TDC) on most vehicles but needs to be retarded(spark past TDC). Also the temperature at which HHO Burns is melting point of the metal it touches. SO...your valves and head would burn through in a matter of weeks. Also when you completely remove gasoline or diesel from an engine the upper cylinder gets no lubrication and will wear out your piston rings FAST.
Getting enough HHO to power a car is pretty hard if not impossible. Explanation: a 2 cylinder 1L engine uses 1L of air per 4 revolutions (rpm). Gasoline is injected as a mist which turns into a vapor instantly at a ratio of 15 parts air to one part vapor. Which is .07 L. At 2000 RMP the engine uses 1/2L of vapor per SECOND. HHO is already one part oxygen to two parts hydrogen so too much air would thin it out too much and give no explosion. SO, even at a ratio of 10:1 that would require .85 L per second of HHO to power that same engine at 2000RPM. Kinda alot. NO generator I have seen or made can come close to the requirements.
So we use HHO to Boost the efficeincy of our gasoline engine, giving it pure hydrogen and oxygen to let the fuel burn better. This is where the good part starts.
Most sellers are selling systems that give less than 1/2 LPM of HHO. When mixed with the air going to the engine that makes NOTHING. 1/10-1/2 LPM of HHO will do some good for a small engine like 50CC-2.0L again more HHO to the bigger engine. Any engine over this size needs 1+ LPM. Alot of the sellers dont even know how much their system makes! They say "ALOT" but in reality all the cells I have tested that seemed to make alot, made 1/4-3/4 LPM. If the kit supplies gas via an aquarium air line, the system makes nothing, trust me. LOOK OUT FOR THE GAS OUTPUT.
Second, if a system uses alot of AMPS, it will fry your alternator and battery in no time which no one will tell you though. Look out for systems that draw over 15AMPs but put out less than 1LPM. This is not a wise investment. A full size truck can handle 25 AMPS but I dont recommend going over 20.
MORE EXPENSIVE DOESNT MEAN GOOD!
Upon testing, I find that without proper circulation of air around a unit (which is impossible under the hood of the car where it is already HOT) the unit boils over in a matter of minutes. So it starts drawing more amps, if you start at 10 you will get above 20 at boil. NOT GOOD.
Any system made out of PVC(white) or ABS(black) Plumbing pipe that draws over 15 amps is likely to boil. That pipe is not made to withstand that kind of temperature. It turns soft and flexible at that temp. It will warp, deform and likely leak in short time if there is any connections below the water line. Watch out for these types of systems.
The biggest concern is that most none of the sellers tell anyone that if you own a EFI (fuel injected) car which most people do, that you will need either and EFIE on your Oxygen sensor, or a resistor on your MAP or MAF sensor. These are fairly easy to build and install but it is a MUST and you will not see much difference in fuel savings without one, you even might see a loss of economy. It is used to trick the computer into thinking that the fuel mix is richer than it is. You want LEAN mix if you are running HHO boost. But too much oxygen in the exhaust will tell the computer to add more fuel which would cancel any HHO boost. Moving the Oxygen sensor out of the pipe but still mounted on the pipe will work on some vehicles (1996o or older). BE WARNED: too lean of a fuel mix WILL burn your valve seats and valve heads! Diesel cars do not suffer from this.
CONCLUSION!
I have tested many systems and put over $5000 into it all, I have built many different cells and tried many electronics. I have come to a conclusion that as of yet, there is no system out there worth "investing" into just yet. The reason for this is that the energy your car has to spend turning an alternator at full load is equal to running your a/c compressor full time and the fact that your battery suffers from this is even more costly. Add it all up and this "investment" isnt quite that. The cleaning of the cell and the measuring of electrolyte is also time consuming.