There could be a whole slue of things that could be causing the delay in activation. Lets say you make 20psi of boost how is that enough to stop a pump spraying at 60psi of pressure. Things like how your activating your system, the I.D of the hose your using all play a role in how quickly your pump will react. And are you using a pressure gauge vs a activation light to show this?
Boost pressure switches have a accuaracy tolerace of + or - 20% but I doubt that's why. Plus the smaller the I.D of hose you use the harder your pump has to work to get the initial spary going this is a issue. Rembember these were designed for 3/8" I.D hose.
There should be no way vac should effect the pumps ability to spray nor boost pressure in the line especially if a solenoid or check valve with a pressure higher than the vehicles boost capability or vac. Now being a pulling force (there is almost no vac before the throttle body blade) A 1psi check valve would do the job in that spot on any car and it won't pull fluid in. Most grand nationals do not even run a check valve because it's really not needed if the nozzle is mounted before the throttle body blade.
If a pump can go from 0 to 180 psi in under a second there should be no reason for a 2 second spray delay in any boosted enviroment with full voltage to the pump. The only pressure it needs to overcome is the boost going past it so even at the minimum 60psi there should be no delay.
Say a 25psi check valve was 4 inches from the nozzle it will always have 25psi of pressure behind it. Water is only pulled under vac not under boost air is being pushed into the motor under boost. At 0 vac no water would be pulled.
If your using say 1/8" ID hose it's going to take the pump a second or two to reach pressure because it has to build up some pressure before the fluid is going to move. But even with that the delay should be less than 1 second.
I'm doing a SRT-4 install on one of the forum members from Canada at my house today and I will give you guys the whole skinny on it. All I know people running larger ID hose don't have this issue.
People with pressure gauges will also tell you it's pretty much instant at least with 1/4" ID hose.
I'll try to find the video from about 2 years ago with a Turbod Civic with a clear intake tube with water injection on the dyno. He was using a older SMC kit but as soon as the light was on the spray started. And this car was making 28psi of boost
I'll have some results for you later on today. I'm on pacific time so it will be up late today.
