When to activate Water injection?

[Philip]

Hi,
thanks for that,
yes the sensor is after both where the water is going in and after the blower. (In the plenum) I havent got the room for an intercooler so i was hoping to use water for this purpose. I can reprogram the ecu to do what ever i want, im currently making it turn water on at 4psi boost as long as revs are over 4200 or manifold air temp is above 50degrees C. I havent got it running yet so these are all guessed figures. I could do as you say and start it at 50% duty cycle and work up to 100% as temp increases. Wouldnt be too difficult, just means a bit of programing and a driver pcb making up. DO these figures look ok to you or are they too low? Ive read that water shouldnt be turned on below 6psi, but i might not reach that level of boost,
Phil