(taken from hhoforums.com http://www.hhoforums.com/showthread.php?t=714)
"The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
*Hydrogen does not fit well into the normal definitions of octane number. It has a very high Research Octane Number (RON) and a low Motor Octane Number (MON) so that it has low knock resistance in practice, due to its low ignition energy (primarily due to its low dissociation energy) and extremely high flame speed. Basically this means that hydrogen will ignite easier and have a lower octane rating at higher rpms and higher compression ratios.
That being said, hydrogen has been reported to have an octane rating of 130, and the fact that some people claim that hho made their knock go away would seem to support this.
However... HHO is 2 parts hydrogen and one part oxygen, so the octane rating and how your engine reacts, one would likely have to take into account the oxygen content as well.
Also one must keep in mind than not all HHO generators produce HHO of the same proportions. As the atoms are separated by the electrolysis. Hydrogen bubbles begin to collect on the (- Anode) plates, and Oxygen collects on the (+ Cathode) plates. So 1/3 of the gas produced is Oxygen, and the other 2/3 is Hydrogen.
Octane aside HHO does make the gas burn more quickly so the more HHO you add in the more you will need to retard the timing.
what I would like to say in summary is: when injecting HHO, less is more."
As far as the efie is concerned it is controlled with a "pot" (potentiometer) you turn the pot to change the offset voltage. Our efies have a range of 450mV. O2 sensors run on a 1V scale so you won't be able to lean the engine to a dangerous point. You want to cut the signal wire, not splice it. Having the efie in the cab is a good idea in my opinion so you can have a friend adjust it on the fly.
HHOdirect is a guy named Bob Volk, he purchases his efies from us and his kit looks good. Go for it. It is a more than fair price, our kits (http://www.dry-cells.com
) are $575.00