Use a 5volt relay, you can get them at digikey.com. They usually work as low as 3-4 volts, meaning near WOT you will activate the spray. You could also hook it to the stock MAP sensor, which should hit 3v after 1-2psi - that might be a better idea.

 

This might be a bit more indepth than u wanted but ----, this is some good info.

http://autospeed.drive.com.au/cms/A_...popularArticle

 

there will always be some people that say things wont work unless it costs alot of money or unless it has a name brand on it. from what i seen it worked great. i ended up hooking it to the vtec solinoid so when vtec hit it would power the sprayer. i datalogged a run where the sprayer was turned off and then another where it was on and it lowered the AIT 15* with the ice water. so in my mind it worked great and did exactly what i wanted it to do. not sure what that would have been on the dyno but i was happy with the results.

 

@ Zeniceguycrx

wouldnt it be a better idea to take all 4 pulses of each fuel injector, and wire them to 1 water injector? so you still have somekind of open/closing on the water inejctor.

@ TCC

thats indeed nice info, but i already knew that site.

@ jeffsciv23

i drove yesterday with my car, and the sick amount of heat that is produced by the manifold is sick!
my hood gets really hot, also the front strutbar get so hot.. (can barely touchit without burning my hand)

the inlet of the IC is hot, the outlet is colder, so ill put it on the hotside. when the chargepies come in to the engine bay, they get hot again...

 

My hood was hot too, get some aluminum tape on the underside of you're hood, it will help ALOT! so you dont burn the hell out of you're paint.