Background:
I always thought that drilling a hole in your intercooler was a bad idea. With a tune and higher than stock boost, I worried about sending my turbos out of their efficiency range by creating a boost leak. Our turbos are so tiny that it doesn't take much extra spinning to make them into hair dryers, adding tons of heat to the combustion chamber.
I bought a used Wagner intercooler which already had a drain hole drilled in it. I was torn on whether I should plug the hole or keep it. After running with the hole for a while I found that quite a bit of liquid was sprayed on the undercarriage from the hole, so obviously it was a useful drain. I decided that I still didn't like having a boost leak from the hole, so I came up with a plan to place a valve on it.
Materials:
-JB Weld
-brass barbed fitting
-vacuum hose
-worm gear clamps
-female spade connectors
-normally open adjustable Hobbs pressure switch similar to this (Hobbs Switch, Boost Activated, Boost Level Adjustable :
atpturbo.com)
-brass barbed fitting for the Hobbs switch
-wire
-fuse
-normally open 12V solenoid valve (I used an old fuel pressure solenoid I had laying around)
Procedure:
I cut off the threads of a barbed fitting and used JB Weld to glue it over the CAC drain hole. This way it was flush with the CAC and the hole continued to be at the lowest point in the system. I thought if I threaded it in, the threads would be too high and all of the fluid wouldn't drain out.
I have a small valve on my air compressor with a detailed gauge, so I hooked it up to my Hobbs switch. I then used an ohm meter to adjust the trigger point of the switch to about 8psi.
Next, I tapped into a constant boost source. Below is the vacuum hose coming off of the upper intercooler pipe to the solenoids on top of the intake manifold. I added a "T" inline to go the my Hobbs pressure switch.
Then I ran wires into the fuse box above the radiator and created a fused connection from one of the open spade connections.
Next I ran wire from the fuse box (+) to the Hobbs pressure switch. Then a wire (+) from the Hobbs switch to one side of the solenoid valve below the CAC hole. Next I found a stock ground location and ran a wire from there to the other side of the solenoid valve (-).
That's it! Fairly simple. You can test that your wiring is working by using a jumper wire between the terminals on the Hobbs switch. You'll hear your valve close.
Conclusion:
So the way this works is the CAC drain flows freely until the Hobbs pressure switch sees 8psi (or whatever you set it to). That triggers the solenoid valve to close, sealing off any boost leak. Once the boost drops below 8psi, the valve opens and the CAC drains away. Now while I'm towing up mountain passes I don't have to worry about my boost leak driving my turbos out of their efficiency range (something that altitude does more easily anyway) and adding unwanted heat into the mix.
Please let me know if you have any questions. I hope this is helpful to someone.