For me it all goes back to the idea that if these gimmicks actually worked they would be bought up by the vehicle manufacturers and put in their products. Every maker is looking for an edge to make their cars, bikes or whatever better than the competition so it's unlikely they would pass up the possibility to improve their product with such a simple addition. Any piece of junk they have to sell with puffed up ads in magazines and "as seen on TV" type sales has got to be such a small operation that Ford or GM could buy them out with pocket change if they wanted to or they'd find a legal way to get around a patent and add it to their vehicles. After all, how long did it take for all automakers to find a way to get around the patent on the electric starter?
exavid, actually water injection works quite well. High performance aircraft, even tractors of the 30's & 40's used it. We have come close to releasing it for production on low production automobiles a couple of times.
The thing to remember is: water injection is like Nitrous Oxide it is just an enabler not a primary fuel. Water injection allows higher compression for more powerfrom the same size engine, allows more turbo or blower boost, allows slightly more spark advance to be run,allows the use of a lower octane fuel, does a great job of eliminating combustion chamber carbon, cools valves, the steam it produces promotes flame travel in the combustion chamber & removes latent heat.
The drawbacks for production are the main reason it isn't used. Any failure of the system that allows water to continue into the engine is deadly for the engine. Keeping the water system topped off by the end user was & still is a big concern. Cold weather usage is iffy at best as system heaters or alcohol is needed.
BUT, just adding water to the intake doesn't add much by itself, itallows other improvements to add up to a power gain.
When you added that water system to your car (or truck) if you would have leaned the carb slightly at light load cruise & bumped the mid range ign timing up a couple of degrees you would have seen a slight mileage improvement.