I have started researching on a HHO(hydrogen system) and believe that it will work. Reallistically you will not get 40 MPG but you can get 20-35% increase in MPG.
I have started building a system.
You will need:
1. HHO booster (hydrogen/oxygen maker) hydolyzer. Smack's booster
2. safety circuit
3. O2 sensor circuit adjustor. (Depending on age od vehicle and CPU engine control).
These are all simple either build your own or purchase. (get places from site I post below)
This is an exciting idea which is not new. The first US patent was in 1913 I think.
Hydrogen IS VERY EXPLOSIVE !!!!!!!!!!!!!!!!
Do your homework.
With this caveat said, I think that it is a very doable and inexpensive way to increase MPG.
here is the Forum:
go to the FILE portion and find the "HOW TO'S" and they even have parts lists and where to purchase and schematics.
I am using :
1. Smack's booster
2. booster safety circuit (no power to booster if enginge not running)
3. Pat Kelly's O2 sensor circuit board modified by myself for dual O2 sensors)
Here is a senior class project done a MS state U. It used a Ranger as test vehicle.
In this experiment they used vacuum in the safety circuit. Vacuum drops to 0 at full throttle and other times. I am using a oil pressure switch relay in the safety circuit instead.
I am still in the build stage for the booster and design /parts purchase for the electric phase.
I should be able to make this for ~$150 or less. If you Purchase it all ~$350 maybe.
I will post here as project moves forward.
Hope this helps.