I have been interested in water injection on and off for years, I just read the article on the Auqa-tune and it just kind of hit me.
Why not put a water feed carburetor in line in between the intake manifold and the air filter-MAF unit.
There are bubbler, spray, and air water injection systems out there, but from what I see you either you get a vacuum leak or engine drowning. It seems the flow can't match the intake air curve for the engine. So this is when it hit me, run a small water tank and an MG style thumper fuel pump to pump water into a carburetor. Have linkage to sync operate the butterflies on the carb and the throttle body and viola, you now have a metered atomized flow system thru the rpm range. No air leak, no drowning, you can even leave the accelorator pump hooked up for a blast of steam. Combine all this with an HAI and I think water atomization can show some super benefits.
I know my Solstice has a thing about humidity and water, GM uses a type of what they used to call a Hot Wire MAF unit, get this thing wet and the engine goes into safe mode untill what ever dries out. The Solstice has a washable factiry air cleaner, put it in the engine wet and the MAF freaks out and the car will only do 25 mph. This relates to the placement of the caburetor between the MAF and intake manifold.
Also I noticed a huge drop in mpg last week when it went from 70 outside to 50 and the humidity went down to 9%. My car went from 29 mpg to 26 mpg, so I started thinking of ways to ad humidity to the engine.
Now as far as caburetors go, there are 2 bbl down drafts, or perhaps a large SU carb from one of smog year MG's. Another big side draft SU would be a Rover 3.5 V8 carburetor. You'll have to play around with jetting and ad antifreeze or alcohol to the mix in winter, but I think it could work.
Best of all its free, new carbs are super expensive and all this technology is out there in junk yards for the picking. This is not reinventing the wheel, so theres no money to be made reinventing the carburetor. When I get my next used car, it will be a rolling mpg laboratory, I can't wait.
My thoughts are: I suspect the drop in temperature had a much greater impact on your fuel consumption than the change in humidity.
EDIT: that said, I did hear some anecdotal info about DIY water injection just this week.
His car failed his smog test due to high NOX and unburnt hydrocarbons, so he added water injection through the EGR circuit ... and passed the next test with flying colours having made no other changes.
He left the water injection on following the test, but noted no change in fuel consumption.
(Of course nothing he said proves anything either way.)
It would decrease economy by decreasing power output without affecting the amount of fuel output by the injectors...
Water Injection does not add power, it is an anti-detonant period.
It is useful only when paired with combustion chamber conditions that far exceed the stability of the given fuel.
Secondarily it helps by cleaning the combustion chamber and general valve area of carbon.
So.... Unless you're running very high amounts of static compression and/or charge temperatures that grossly exceed your fuels ability to pre-ignite under light loads, it would not be useful.
It would also destroy cheaper quality MAF's... aka Ford, GM, Nissan, while at the same time shorting out any IAT, or MAF sensor it comes in contact with. Remember that at some level it will be coaxed backwards up the intake...
wi is not a fuel, it is a cleaner and an anti-detonant.
on an engine that is NOT experiancing power loss due to pre-ignition, running pump gas + wi will have the same end result as trying to run 105-110-115 octane pump race fuel in it.
the engine will:
bog on tip-in throttle enrichment
using fuel that is more stable than required always lowers power output. the only way to offset that is by running the more stable fuel it out of conditions the less stable fuel can be run at.
you put race gas in a stock engine and it'll drop power, economy and throttle response. the flame front is too slow, and the overall entire combustion process simply takes too long. all of that fuel that can't be used in the meaningful portion of the expansion stroke simply flies right out the exhaust pipe
the exact same thing happens when you put water injection to an engine that can't benifit from a higher octane fuel.
most things associated with water injection are complete myths:
the state change is meaningless in the combustion chamber!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! (it does not create some magical steam power to push the piston down...)
wi does not appreciably cool the incoming charge temp (it is exposed in the charge for milliseconds before entering the combustion chamber, while the thermocouple you shove in the intake tract trying to "prove" it does cool it is exposed to evaporative cooling in an extremely high velocity of airflow for aslong as you want it exposed...)
the amount of air/fuel displaced is inconciquential
wi cools the various combustion chamber faces itself only a small amount at most
water injection is, and never has been anything more than a cheap means to raise the effective pre-ignition resistance of the fuel you're using. it's the poor man's race-gas.
If you're not running an engine that experiences pre-ignition <cough>forced induction, or a grossly high effective compression normally aspirated engine <cough>.
you don't need a higher octane fuel, race gas, or water injection.