I have been doing some research on water injection for my 1.6l 16v.  The results that I have found all seem to be good improvements in HP and economy.   I know that this is a great mod for a forced air induction engine to keep the intake temps down.

Has any one tried water injection on a normally aspirated engine?  

You can add up to 50% of the fuel flow
in water or Alcohol/Water mixture, over
50% alcohol water has no additional benefit

I don't know if you will really get any improvments
in performance, you can advance the timing with
less or no ping, I think you will need to increase
compression in a N/A engine to get real HP gains.

On the other hand, lowering compression and
adding some forced induction is a good way to use
a Water injection system, and one that I can say
is too much fun in a Zuke    

Wild

pure water?

when i was planning on turbo, i was told to use 50% water to 50% metho for injection to keep temps down.

maybe its different?

Under boost the alcohol adds additional
fuel to richen up the mixture, as well as
boost the octain during boost.

Water works fine, but adds no fuel to the
mix, just reduced detonation

if its mileage your looking for add about 5 oz. of acetone to your zuk but no more, and for a diesel like a power stroke add no more than about 2 oz per tank full, you can gain as much as 31% mileage per tank.