We are working on a rather long HHO injection thread on FTE, is it OK if I were to post a link? Several (some long time) members are reporting promising results with generators they built. This is something simple enough that almost anyone can try it to see for themselves if it works. My first attempt didn't work well enough to fit on the engine, so I'm back to the drawing board.
Hydrogen gas has a self ignition temperature of over 900F, so a backfire through the intake or preignition in the chamber is not something you have to worry about. Don't ever use salt as an electrolyte though (produces clorine gas). Baking soda is ok, lye or KOH will work better, but for casual testing baking soda is probably the safest as it is not caustic.
For fuel economy, its been a long line of mods and upgrages for my truck.
It had a C6 transmission and 4.10 gears when I bought it (tach was messed up so I thought it had 3.54
). At 60 MPH it got 9 MPG on high sulfur diesel. After swapping to 3.08s, and adding a ram intake the averaged went up to 16-18 MPG and on rare ocasions 20 MPG empty, but that changed with LSD and ULSD. My average with 3.08s was closer to 13 MPG becasue I was usually loaded or towing a trailer at 70 MPH.
Adding the E4OD was an improvement. In 3rd gear towing or loaded, 15 MPG was now the norm, the locking torque converter makes the difference. Overdrive can't really be used unless I'm empty or at least fairly light, but it is a pleasure to drive when I am able to use it. 1650 RPM at 70 MPH and usually gets at least 20 MPG consistently at that speed. Also because of the tall gearing, moderate engine loading and relatively low RPM, I have adjusted the cruise control to apply only the slightest amount of power to keep the truck going at my cruising speed. This seems to have made my 20 MPG runs more consistent and has removed one major variable in my quest for better MPGs; my right foot. Speed will typically bleed off by up to 5 MPH on the longer hills unless its a very steep grade, then I have to hit the OD cancel switch and take over until I get to the top of the hill.
The turbocharger didn't seem to do much for economy, but it most certainly did not hurt either.
I recently got a set of toyo open country HT highway ribbed tires and they seem to be doing well. The stock 235/85/16 tire size is probably the best configuration for fuel economy when you consider the increace in ride height and frontal cross section even with 255/85-16 tires, let alone the larger off road tires.
I have also removed my canopy from the truck, and when I am empty I have the tailgate up. Have not tried with the tailgate down or removing it.
All my estimates are for 70 MPH cruise speed except for when I had those darn 4.10 gears. I also live in a rather hilly part of the world and 2% grade is about as flat as it ever gets. I run the same 200 mile trip nearly every week, so I was able to establish the average very well by now.