Straight waters effect on the A/F of a wideband O2 meter?

[XX4me]

I've read most of the posts here and can't find what effect the WI has on wideband O2 meters.

Example being if I'm running an A/F of 12:1 without water will it remain the same with water.

[Richard L]

We have touched on thsi subject many times but nothing too conclusive - is it possible to tune for 12:1 first and add water later and see if you notice any changes.

[XX4me]

Unfortunately I can't without getting unleaded race gas.
I'm running 18psi on 93 octane pump gas with an intercooler and H2O injection.

[Richard L]

You can turn the boost pressure down to 10-12psi and try it, the lambda will not notice the change of boost pressure.

[tici]

I tried with my blowed 5.7L LS1 engine (6 PSI Vortech) and I saw no difference with or without water.
Right now I'm tuning that way for 12.5 AFR, then I'll switch to 50% alcohol.
Water alone allows a certain pressute/timing being on the safe side.