I'm certainly not the first person to do this, but I haven't seen anybody else get this good of results for so little money. With that being said, I'll continue with the post, which is really just a copy/paste from my blog. Since this was originally a blog post, it does not have the traditional step by step DIY format. Sorry about that.
Once I felt my intercooler after a few runs of auto-x, I knew I had to do something about heat soak. An intercooler sprayer seemed to be a relatively cheap/easy way to help deal with that. My goal was to cleanly install a quality IC sprayer for $40 or less. It's hard to do much of anything car related for $40, let alone something nice. Because of this budget, I went to ebay. I found a pressure switch that is perfect for this project, and a windshield washer kit. You can do this for even less money by not getting the pressure switch, but I wanted an automatic setting that runs the sprayer once a certain level of boost is reached. I also had to get a few misc items from Home Depot, but even so, I did a pretty good job of sticking to the budget.
This is the pressure switch I got: http://www.aquastealth.com/browsepro...re-switch.html This same item can be purchased on ebay for the same price. The one that can be triggered by 2-24psi is ideal.
This is the sprayer kit I got: http://www.carparts.com/autoparts/Pr...dshield+washer The overall quality of this kit is pretty low, but the pump and tubing, the only parts from it I used, are great. Also, it was $15. This kit does come with nozzles and a reservoir, but both are complete crap.
To save on weight, space, and money, I tapped into the windshield washer reservoir. To do so, I drilled a hole and added a brass fitting that I got from Home Depot. I then threaded it in and sealed it with silicon caulk. The pump is also mounted on the OEM reservoir. On my car, the tank is mounted inside the bumper/fender. To gain access, you will need to jack the car up a bit and peel back the fender liner.
Since I am using a pressure switch to trigger this, I had to run a boost line to the inside of the car. You could always mount the switch in the engine bay, but for the sake of reliability, I mount all my electronics inside the car. I already had a boost gauge that is tapped into the hose exiting the bypass valve, so I fitted a different tube to that and used a T splitter inside to enable both the pressure switch and the boost gauge to get pressure readings. At the same time, I ran a wire from the pressure switch, though the firewall, and to the sprayer reservoir where the pump was to be mounted. I also ran the tubing from the IC splitter down to the tank, because it follows virtually the same path.
For the electrical side of things, I put 2 switches in the change compartment/fuse panel door. The rocker switch in the center puts the sprayer on automatic, so that it is triggered by a predetermined amount of boost. The red push button(came with the sprayer kit) sprays the IC regardless of the boost level. This button is intended to be used between auto-x and rally-x runs to help combat heat soak. The pressure switch has 3 pins. One is "common", which I connected to the pump, the other is "normally closed", I connected this one to the push button. The 3rd pin is "normally open". I connected this pin to the rocker switch. For power, I tapped into the anti-lock brake fuse slot. I already had wires coming out of this spot for a disable switch, so that was easy. I used a 10 amp inline fuse to protect the sprayer system. The switch on the left is unrelated to this project, but it disables the anti-lock brakes.
When it came to nozzle selection, I was unsure as to which path I would take. The nozzles that came with the kit were junk. They were made of plastic and had terrible spray patterns. I thought about ordering nozzles from Mcmaster, but, at $10 each, they were horribly overpriced. I had some extra tubing and a T splitter laying around, so I made a ring of tubing to go around the perimeter of the IC. I drilled small holes in the tube, and ended up with a nice even spray that covered the entire IC. I mounted the tube with zip ties. I drilled a pair of holes in my splitter every inch, and ran the ties through those. My splitter was a DIY project, as well, so I drilled into it without hesitation. I have yet to get one, but I would highly suggest putting a check valve right before the nozzles(in my case, tubing) so the system will be more responsive. Currently, there is about a 1 second delay between when I push the button and when water flows out.
And here is a video of this thing in action. As you can see, it has a pretty healthy spray.
I'm pretty happy with how this ended up. It certainly won't have a big impact on performance, but it was cheap and added minimal weight. Also, anything that reduces intake temperatures will provide some benefit. If you're thinking about doing this mod, I say go for it.
I have some more DIY things on here: http://www.cgbagne.com/wrx/