Ethanol can be used if the system components will tolerate it. The board was started by those with affiliations to Aquamist (but is meant for all) so that is why you will see a lot of no ethanol comments.
Water is being used for knock suppression only. You want to inject enough to suppress knock sensitive areas which are usually more correlated to torque/cylinder pressure than load. Load is more of a type of proxy for torque/cylinder pressure but not identical. You do not want to inject so much water as to displace fuel that would have been consumed in combustion. For instance you can displace fuel from a lambda of .6 to a lambda of .85 - but you would not want to reduce your fueling to higher than around .85~.90 which would be your optimum power AFR depending on your intake and cylinder mixing efficiency.
Alcohol in the mixture is good because you can reduce gasoline in the mixture further and the alcohol will burn in its place - making it a hybrid fueling. Once you do this though be careful using AFR and try to work and think in lambda since lambda is a consistent measure between different hydrocarbons.
The amount of water to inject will really depend on how much gasoline is currently being used for in cylinder cooling and detonation suppression. If a lot of gasoline is being used more water can be used while leaning out the gasonline mixture. If only a little bit of gasoline is being used to suppress knock - less water should be used. In any case injecting alcohol will permit gasoline to be leaned even further than water alone. As a rule 10% to 25% water to fuel can be used - but you will see applications all over the range.
Whatever system you use you want to bench test for how much flow your system actually generates no matter what the specs of the components are. Then take into account the reduced flow from boost across the jet face.
Injection should only be being used at higher torque generating conditions. You shouldn't be in those conditions before being warmed up in any event. Even without water injection generating high torque before being at operating temperature will damage your oil from the rich warm up fuel settings. Generating boost before getting to operating temperature is always a bad thing.
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