Just to clarify what I was trying to get over in the last post - The email Richard sent me does leave a few grey areas in it's translation and we did have a brief email conversation at midnight ... we were a bit tired and the spelling was getting a bit poor as we had both had a long day I think !
From the Subaru forums (and my own experiences) external water misters that spray a mist over the outside of the intercooler don't work very well. In my Scoobie STI I never noticed any difference and other forums where modified non-STI imprezas ask about the conversion are often told just not to bother retro-fitting the kit even though it's only about £100 for the bits- it might look trick and be a talking point, but in cooling terms it might get you a few degrees C reduction from a standing start but that's about it. Richards testing tries to back this up saying that in his testing, an external mister didn't reduce the temps by very much (if anything) when used for about 10 minutes continuously. I know the sprint uses a mister but it seems that was the act of a desperate man more than anything
(strangely enough one of the most talked about conversions is modifying the standard Subaru legacy charge-cooler (air-water) to fit imprezas).
Now on to the internal water injection bit .. (I know thorney and some others probably know the differences and principles, but I'm just trying to clarify for the masses
)
I for one know that on cold damp mornings my cars go better - you can't obviously notice this all the time, I think because it often goes hand-in-hand with icy/wet roads so foot-to-the floor isn't everyone's cup-of-tea during this time. Think back to those cold December mornings and how crisper the engine feels. This is due to both the air being denser (cold) and water moisture being present which the engine likes.
Typically when a WI (Water Injection) kit is fitted, water 'vapour' is injected into the engine inlet tract triggered by high boost pressures. On normal turbo cars (Impreza, VXT etc..) the guidelines are to put a single injector just before the throttle body (it's put here so that the vapour has less distance to travel to the engine once it has been activated so there is less of a delayed effect. If you put the jet further back along the intake system (say around the intercooler) then the vapour would be evaporated away before it hit the engine which would not stop engine knock, but would lead to lower intake temperatures, though.
Richards testing leads him to believe that the best system seems to have two jets, one injecting vapour into the engine by the throttle body, the other injecting vapour into the intercooler (internally) which is how he got his low temperatures. By just having the one jet by the throttle body he could see the temperatures rising, but with the extra small jet into the intercooler, these rises went away.
He believes that the sprint will not have the two-jet setup (probably just a single jet was fitted) as this is a more recent finding.
An interesting fact is that he claims they were using 70cc of water injection per minute (only during max boost) in their testing. This might seem a great deal of water to be chucking into an engine, and might logically seem to not go hand-in-hand with the fire/explosion/combustion that's going on in they cylinders, but remember that when you drive your car in the rain, it is probably taking in about 150cc of water at that time anyway from the water saturated ambient air !
Thankfully, Richard seems to be an enthusiast about their product and likes nothing better than to have people get maximum benefit from it. I for one do not want to start drilling holes all over my intake system trying different setups (which is why I started this thread !) but hopefully he can come back with some 'Specific' information on the VXT on how well it all works (if at all).
Best thing of all is that it's a British invention, a british product made here in the UK, the world leader in the technology exporting world-wide, and they used water injection in the spitfire during WWII to get higher supercharger boosts when dicing with then pesky ME109's over the channel
Another useless fact.. (I'm full of these
), The engine of the Harrier jump jet is so highly stressed that they have a large water tank sat behind the pilot that injects water into the engine to stop it from blowing up ! Without this water, the engine would quickly give-up the ghost ! (I used to work on an RAF aircraft maintenance field).. VXT with water injection.. dices with M3's and Merc's down the M4 .. is history repeating itself ?
Watch this space
Thks
PAul
A couple of points. The Sprint DOES use water injection (trust me on this), secondly the WRX has the engine at the front with a great big rad and excellent airflow, we do not. Subarau use the misters to great effect as they're there to simply calm things down under full boost situations, you'll be asking the misters to act as aditional engine cooling - not their design.
However thats not to say they're not a bad idea, I'd be interested simply for education purposes but I seriously doubt misters on their own could drop intake temps low enough to do the required job. (if they can then I reckon you'll need a trailer to carry the water bowser 
