general tuning (with WI) questions

[cabe]

i understand the concepts of water injection, and will be setting up a direct port water injection system on my turbo 4cyl with a map for a secondary set of injectors that my ems provides me with. i believe that this will provide me with the most flexability. still, there are a few things that i do not know the answer to. here goes.

the one thing i still cannot understand is why the 12-12.5 number keeps coming up when people say "richer than 12-12.5 and there will be no more o2 to burn fuel" when i am under the impression that 14.7:1 is stoich.. i have a feeling that this somehow has to do with the fact that fuel does not react with just the oxygen in the air at high combustion temps. clarification greatly welcome. :wink:

anyway, the way i understand it, the tuning process should consist of a few things..

1) tuning the afr at each load/speed point so that there is no excess fuel left over after combustion (only a system with a seperate injector driver would be able to tune like this due to differing ammounts of water needing to be injected at different load/speed points) however i have no idea how i would determine the correct afr to shoot for.. anyone have any suggestions?
2) a balancing act between injecting water and advancing timing until peak torque is reached at each load/speed point (which would obviously have to be done at a load holding dyno)

^-- now there is nothing in there about keeping the water to fuel mix below any ratio (25% etc) because i could not find any reason in my research why there should be a cap on how much water to fuel there is. (maybe this is because not many people are doing it with a secondary bank of injectors dedicated to water injection, and thus do not have the flexability to tune at all load/speed points?)

sorry for the long post and thanks for taking the time to read this far :smile: . (constructive) comments on this are greatly desired!