Since you at one point ran a similar setup, would you happen to remember the correct connections? More specifically the connections made to/from the N75? I have the Snow Performance instructions on how to wire and connect the wastegate solenoid, but when it comes to the N75 portion it gets very general and just says "Manual Boost Controller/Boost Solenoid". Since our N75 has 3 ports, it would be nice to have something (diagram/photo) to check my connections against.
I was bored at lunch and looked into this a bit. The solenoid that goes in between the N75 and stuff is the same MAC solenoid most places use for stuff. It's the same one on my AEM boost controller.
When powered, ports 3&1 are connected. Not powered ports 3&2 are connected. Looking at the front of the solenoid, front port is 3, left is 2 and right is 1 (should be labeled).
The N75. The metal port is boost. The port parallel to that goes is the vent and goes back into the turbo inlet. The L or perpendicular port goes to the wastegate. When you are making boost above wastegate pressure, the N75 pulses and connects the metal port to the vent port. When you are only making wastegate pressure, the metal port and the L (wastegate port) are connected.
From what I read, the controller (or whatever) should send 0 voltage to the solenoid during favorable circumstances. So in that situation, you want boost to be able to flow through the solenoid, so ports 3&2 connected. When it failsafes, it will send voltage to the solenoid, connecting ports 3&1, which at that point you would want the boost being vented AROUND the wastegate to be directed back AT the wastegate to open it up.
So the way I see it, it should be plumbed as follows:
BOOST: Comes from the port by the DV and goes to the metal port on the N75. You 99.9% already have it this way or you wouldn't be making boost.
VENT: From the N75 (the port parallel to the metal port) should be plumbed to #3 on the solenoid
#2 on the solenoid should go to the inlet on the turbo
WASTEGATE: The L port on the N75 should be T'd with #1 on the solenoid and go to the wastegate
This way, with the solenoid not powered, boost flows as it should through all that stuff. When the solenoid is powered (failsafed) the vent pressure will be directed to the wastegate to open it up and cut boost. Let me know if all that makes sense. Like I said, looked around during lunch and did a brain dump. LOL