Most people refer to WATER sprayers when they speak about intercooler sprayers, although the companies that make nitrous kits also make nitrous sprayers, which sprays much, much cooler. I have heard of guys putting ice water in their IC sprayer reservoirs on track days.
To know how a sprayer system works, you have to know how an intercooler works, which you probably do already.
You already know that hot air from the turbocharger goes through the IC and heats up the metal fins. Or another way to look at it is the metal fins remove heat from the air inside the IC, thus lowering the temp. On the outside of the IC when you are moving the cooler air rushing past, the fins do the same thing, the cool air pulls heat from the metal. This is why people like to use intercooler spray systems. A light mist of fluid like water will pull more heat away from the metal and then in turn form the air going into the motor. Basically it's eaporative cooling.
Not long ago there was a guy who set up some temp. probes on his TMIC, which had a home-made water sprayer (he used windshield washer fluid sprayer pump, etc...) He took readings before and after spraying water on his intercooler. Anyway, it turns out that while the car is going fast, the spray hardly does anything, because there's plenty of cooler air passing through the IC fins. while the car was stopped or in city driving however, the spray did make a pretty decent impact on the IC temp.
RED_DET - Thanks for the swap info. I did track down some additional info on G20.net and SR20forum.com. Both of those sites have more transverse SR guys than Nicoclub, apparently.
Regarding heatsoak on my Subie, check this out:
http://www.speedmonkee.com/det...ID=56 It has worked great for me in preventing heatsoak to the point where I'm amazed at how effective it is. Where my IC used to be hot to the touch on summer days after stop-go traffic, now it's just slightly warm. The chimney shield works by diverting hot air from the turbo up out of the hood scoop while you're stopped, and at speed, it diverts some air down right over the turbo. I'm sure it doesn't cool the turbo down much, but at least it's keeping that air moving down and away from the IC.