water injection requires fuel alteration ?

does the use of water injection requires alterations to the fuel strategy ? like does it require more/less fuel te be injected while spraying water in the engine intake to keep the afr's constant ?

is water injection benefical on a boosted engine run on E85 ? or would playing with injection timing be as good to extract heat in the intake charge

My thoughts, which may be incorrect.

It shouldn't, you're still supplying the fuel to match the air entering the engine.

If you were to use an alcohol mixture, you may find reducing the petrol/gasoline might help as the alcohol will also be burned - going to be trial and error.

Well, usage of just water spray usually richens the mixture a little bit as water replaces some air in combustion chamber.

Water injection on boosted engines with E85 is also efficient as water has much higher latent heat evaporation ratio comparing to petrol and ethanol- it is especially beneficial with very high boost levels. Water cools down combustion chamber temperature big time allowing to advance ignition timing to get more power..

AS above comment by Shota but make sure you use fail safes !

Uh, I may be missing something here, but while the evapored water vapour does indeed displace some of the oxygen bearing gas entering the cylinders, that also means less of that air is going to be drawn into the engine - so it 'should' be self correcting?

Of course, with any alcohol content in the "water", there will be an imbalance from the additional fuelling.

It will be the case with MAF system but it will take a while to adjust. With speed density system it will not adjust automatically unless closed loop mode is activated...