I have a little to add......
AIR TO WATER
You are also limited by heat soak of the water, once the water becomes heated it will only cool so much due to the small coolers that most companies supply in their kits. Its definitly not as efficient as air to air but it is more practical when dealing with limited spacing.
Spraying on either intercoolers or blower housings are another way of helping to control boost temps.
One way is to use high pressure liquids/gases using a spray bar or injector to where the liquid is administered to the outside of the intercooler (or a roots blower housing) in which the liquids cold temperature OR high rate of evaperation supplies additional means of cooling.
Different brands used are SnowPerformance, Cryo Cool and of course Nitrous.. do NOT confuse the Cryo Cool spray bar with the "bulb" setup... the bulb is VERY inefficient and is not worth mentioning any further.
Even though SnowPerformance and Nitrous can be used as an external means of cooling they are FAR more effective if you inject them INTO the boost. When injected they are better atomized and transfer heat at a higher rate (actually in this case it would be removing heat)
I'm not going into the cooling properties of nitrous... since its obvious about how and why its used.
Meth/Water injection is a great way to cool your boost... in an experiment that Tom showed me we sprayed Meth on the outside of an intake manifold and even without running the car the manifold became cold to the touch... I would guess by 20*F if not more, so you can imagine how good it would work if you injected it directly into the boost.
The biggest and most obvious con is that with ANY form of chemical cooling you have to keep refilling it and refills aren't free. BUT when you are limited by space or design (roots/JRSC) chemical cooling is still better than no cooling at all.
Personally I use Meth injection, but only as a SAFETY system I do not tune for it.
[B]1951 McCormick FARMALL M
2007 MINI Cooper S Turbo... new project car
1998 Chevy 3500 Ext cab, long bed, 4x4, duelly, turbo diesel
2004 Harley V-Rod.... sex on wheels
2011 Harley Electra Glide Ultra Limited