It is quite funny to watch idiots yelling scam on things that are definately not a scam - but I will skip that conversation for now.
If you are planning to generate this HHO for catalyst use on a car (to help the gas burn more efficiently) you will want to build an electrolyzer that draws no more than 20 amps. Depending on your array you might actually want less than that - sometimes you have to experiment to see where you get your peak LPM output. It could be 2 amps, could be 10, could be 20... It's also a good idea to draw the experimental power from the auto you are going to use the unit in, as the alternator and electrical system can have an effect on that optimum amperage, ie amount of baking soda.
The best thing to do is to use an amp meter to measure the draw of your cathode/anode array while in plain tap/distilled water (whatever your using). Obviously it depends on how much water you are using, but if your in the standard 1.5 to 2 liters for your electrolyzer start with a 1/2 teaspoon. Your optimum draw should be several amps less when cold so keep adding little by little (1/2 teaspoon) until you get to yor optimum amp draw. Make sure to stir as you go because it may take a minute for each 1/2 teaspoon to dissolve.
This is just very basic info to give you a general idea of how it works. Do your research either on the web or by experimenting yourself. You will find there are a lot of variables and tricks that can either hurt or optimize your LPM output.
IMHO, if you have to use anything besides tap water, you need a better cathode/anode array. There are plenty of designs out there than will give you about 1.5 to 2 LPM without the BS, etc..
Mine puts out about 1.5 LPM, which increased my BMW's mileage from 26 MPG to 42 MPG HWY.
I used to be able to go 400 miles on the highway on a full tank before the light came on... now with the HHO on I can go almost 700.
Don't listen to these people talking laws of physics crap(thermodynamics,etc).. they apparently have never heard of how electrons rotate around the nucleus of an atom, etc. Plus your not getting something out of nothing.. there is nothing such as nothing... even the ether contains massive quantities of energy just waiting to be tapped. The people who believe in some of these laws of physics relating to energy will be looking like the idiots that used to insist the earth was flat pretty soon here.. suck to be them!