When to activate Water injection?

[Philip]

Brad,
I had wondered wether it would be smooth enough as Ive no experience with this sort of thing. Im currently adding some code to my ecu to switch a valve from 80% duty cycle to 100% as boost increases from 3-6 psi. It will still be stepped but in 0.5psi steps. This will need some work before it is finished so will end up with my first idea to start with then change to this later. One question for you, any idea what sort of frequency the Aquamist fast shutoff valve works well at?
Thanks,
Phil