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Installing an APEXi AVC-R 
Electronic Boost Controller

Now the cruise control and ABS harness can be reinstalled, followed by the cruise control unit. 
Next comes the solenoid valve. This unit needs to be fairly close to the wastegate actuator, but not so close that it gets exposed to high heat. I chose the opposite wheel housing for this component, as there was plenty of room after installing my APEXi Power Intake. 
Solenoid Valve.JPG (60074 bytes)
As with the pressure sensor, the wire harness was routed from the center console, and the two wire leads for the solenoid valve protected within a length of ribbed sleeving. The unit comes with a rubber mounting pad to reduce the noise level when it operates, however, I found that it was still too noisy in this location and I am planning on relocating the solenoid to a quieter location.
Here's a photo of the wastegate actuator, showing the two vacuum/boost lines. 
VSV Hose-01.JPG (82252 bytes)
The hose on the left connects to the turbo housing, while the hose on the right leads to the turbo VSV. 
Remove the hose between the turbo housing and the wastegate actuator. I used silicone vacuum hose, and ran a length from the solenoid's "NO" hose nipple to the turbo housing nipple. The solenoid's "COM" nipple is joined to the wastegate actuator with another length of hose. Here are a couple shots of the new connections: 
VSV Hose-02.JPG (82530 bytes)
Solenoid-to-VSV Hose.JPG (69021 bytes)
To disable the turbo VSV, remove the hose from the left side of the wastegate actuator. This leads down to the VSV:
Cap VSV-02.JPG (54288 bytes)
Cap both ends. You must securely clamp the cap on the wastegate actuator nipple, or you will experience uncontrolled boost (as I learned firsthand). Here's a photo of the rubber hose plugs I used, before they were clamped down:
Cap VSV-03.JPG (72341 bytes)
The cap on the wastegate actuator later developed a hole, so I installed a length of silicone hose with a tight-fitting plug in the end as a (hopefully) permanent solution.

All that remains to complete the solenoid installation is to join the two halves of the electrical connector.

UPDATE (May 4, 2001)
Annoyed by the loud clicking of the solenoid when under boost, I decided to relocate the solenoid. I fabricated a simple aluminum bracket and secured it to one of the unused airbox mounting holes using some rubber isolation washers and a stainless bolt. I then placed the solenoid on a 1/2" thick pad of Sorbothane, a type of polyurethane used for isolating vibrations and secured the solenoid to the bracket with nylon bolts to further eliminate the clattering of the solenoid. Here's a photo of the updated installation:
Solenoid Bracket.JPG (101746 bytes)
This completely stopped the solenoid noise from reaching the cabin, and also shortened the length of the vacuum hoses to the wastegate actuator, which improves response.
At this point, you are ready to make the splices into the ECU harness. My notes on installing the J&S Safeguard can be consulted to detail how I ran the wires into the trunk.

The following instructions worked on my car, a '93 U.S.-spec Turbo. The warnings about "you are on your own" are doubly important in this, since you can fry your ECU in the worst case scenario. 

At this point, stop what you are doing and disconnect the negative lead of your battery. If you have enabled the security features of your stereo, be advised that you will need access to the security codes to re-enable it when power is restored.

The ECU has 3 connectors. According to the BGB, "A" is the 22-pin connector, "B" is the 26-pin connector, and "C" is the 16-pin connector. The pin numbers below match the BGB designations.


I ran the following wire colors from the AVC-R harness to the ECU harness:

AVCR-to-ECU Connections

AVCR Harness
Wire Color
ECU Harness
Pin Number
ECU Harness
Wire Color
Red A12 Black/Yellow  
Purple B3 White/Red  
Green B26 Brown  
Black B26 Brown  
Gray C14 Pink/Blue  
White A9 Purple/White  
Once you've finished splicing into the harnesses, you can reconnect the battery. 

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