Wastegates control the amount of boost turbos create. When they areclosed, the turbo is the only pathway for air to follow. When thewastegatesopen, they allow an alternate path for air to move through, allowingboostto drop. The wastegates are controlled by a pair of actuators that movedepending on the amount of vacuum pressure applied to them. In stockform,the amount of vacuum is a function of the entire system. With boostjets,the amount of vacuum is restricted slightly, keeping the wastegatesclosedlonger, but vacuum is still a function of the system. As a side note,thestock design has a set of boost cut solenoids in the vacuum pathway tovent any vacuum from getting to the wastegate actuators. The stockwastegate springs, set at 6 psi, are the only things controlling theboost as a fail safe. This is known as 'safety boost'. Generallywhen an EVC is installed, these solenoids are removed from the pathway.This is good and bad: Good because there's no more safety boost. Badbecausesafety boost exists for a reason, to protect the engine's functions.Operationof an EVC (Electronic Valve Controller) or boost controller is prettystraightforward. It regulates the amount vacuum applied to the wastegates tocontrolthe total amount of boost produced. The wastegates are now controlledindirectlyby the electronics, still utilizing vacuum provided by the system totheactuators, but in a more controlled fashion. It uses a solenoid tomaintaina specific vacuum. In the case of the AVC-R this is accomplished bycontrollingthe solenoid duty cycle which determines how long the solenoid staysclosed vs. open in a 40 msec cycle, and can be based on RPM, Gear, andInjector Utilization. Another nice feature of the Apex'i AVC-R is thatwill allow monitoring of a series of functions such as boost pressure,duty cycle, injector utilization, RPM, etc., and can provide a peak holdor a linear map of the results.

For more information on the AVC-R, take a look at http://www.apexi-usa.com/superavcr2.htm

The following procedure is compiled from three installations on '90-'93TTs

Special Tools:
Drill and drill bits Carbide bits if mounting the solenoid on thefront bumper.
Soldering iron
Solder

Other Items:
Electrical Tape
10' to 20' of ¼" vacuum hose 
Although hose comes with the kit, it wouldn't hurt to get some extra,and it's cheap. Re-using the stock boost hoses (the orange lines in4.)requires 10' of hose. To replace everything requires 20'. The differencesare explained later.
2 - ¼" Barrel connectors
Zip Ties Both short and long. The ones provided won't be enough.
¾" #12 nuts, buts, and locking washer or self tapping screwsForthe solenoid mount
½" #10 self tapping metal screws
A pair of self tapping metal screws
2 - ¼" Hose clamps
Wire coat hanger

Preparation:

1. Read these instructions entirely and make sure to have all the itemsand tools necessary. This includes an inventory check to make the AVC-Rkit is complete. Make sure to get everything now as not to be missing somethingthen suddenly having to go out and get it, only to find the store is nowclosed.

2. Use picture 3. to locate the following items on the car:
ECU location (passenger floorboard, not shown in 3.)
Boost solenoid electrical connector (one on each side of engine)
Vacuum hose on passenger side of balance tube (pressure sensor tiein)
Fender opening beside the battery and firewall access inside the passengerfender well
stock vacuum hose that goes to stock solenoids (boost hose connectionin 3.)

Procedure:

There are 5 distinct components to the installation:

I. Run wiring harness and splice into ECU
II. Install the pressure sensor
III. Install the solenoid and all vacuum hoses
IV. Install and connect the display unit
V. Set up the AVC-R parameters
 I. Run the Wiring Harness and Splice Into the ECU

1. Disconnect the battery ground. Turn the steering wheel all the wayto the right, exposing the rear of the passenger fender well.

2. Remove the windshield trim overhanging the battery. There are typicallytwo plastic phillips type connectors. If careful (and they're not too brittle),unscrew the center 'screw' then pop them out and reuse them later. Loosenthe terminals of the battery and remove them. Remove the battery bracketand then pull the battery and take care not to sit it directly on the groundwhich will cause it to drain and be ruined. It's best to sit it on a tableor a piece of wood. Locate the hole in the fender wall at the base of thebattery compartment. It may have a black plastic shield covering it whichcan be removed. (6.)

3. Next remove the screws on the passenger fender liner (7.)to gain access through the firewall into the passenger floorboard areawhere the ECU is located. If there is a mud guard installed, remove itto get full access. 

4. Expose the ECU by pulling up the passenger floorboard carpeting.Use a 10 mm socket to remove the 4 bolts holding the wooden panel in place(8.- White circles). Remove the running board trim (8. - Yellowcircles). Remove the passenger side kick panel. There is a sunkenphillips head screw that holds it in place (8. - Green arrow).

5. Feed the AVC-R wiring harness through the hole by the battery (6.).Use a straightened coat hanger and electrical tape one end of it to theAVC-R wiring harness where the bundle of colored wires is hanging out.This will help feed the wiring harness through the firewall. Look insidethe fender well and pull loose the big rubber boot that protects the mainwiring harness. (9.) This exposes a hole through the firewall. Feedthe coat hanger through the firewall and it will poke out in the ECU compartment.Get inside the car, grab the hanger, and gently pull the AVC-R wiring harnessthrough. Also have pull the display unit connector of the wiring harnessthrough. Make sure to pull enough cable through to connect to the displayunit in desired mounting location. More on this later. Remove the coathanger from the harness. I use an Xacto knife and cut a notch in the rubberfirewall boot so it can be put back in place and allow the AVC-R harnessto rest in that notch.

6. Remove the ECU from the floorboard (3 x 10 mm screws) (10.)Then remove the ECU harness cable by unscrewing the plastic holder (1 x10 mm) (11.). Now the tricky part. The AVC-R wiring harness needsto be spliced into the ECU harness. If using snap-on 'piggyback' connectors,this will go fast. All three of the installs contributing to this pageuse a solder splice for a more secure connection. Refer to picture 12.for splice points. Note that the circles show the relative locationof the connection. They are not necessarily circled around the proper wirecolor. The following table shows the relationships of the AVC-R harnesswires to the ECU wires.
 
 

 

Function	AVC-R Color	ECU color	Pin #
IG Power	Red	White	59
RPM *	Purple	Yellow/Red	07
Ground	Green	Black	50
Ground	Black	Black	50
Throttle	Gray	White	38
Speed	White	Yellow/Green	53
Scramble	Orange	N/A	N/A

*The purple wire from the AVC-R is either connected to the RPM signal(as shown in the chart) or to the injector wire. All three installationsfor this page have connected it using the RPM signal on the ECU.

NOTE: For the ground wires, splice both the green and black wiresto a single ground wire on the ECU. Splice the GREEN wire closest to theECU connector and splice the black wire 1/2" further away. Sounds odd,but is rather critical.

My preferred method of splicing is the military splice. It takes a bitmore time but guarantees a solid connection. Take the target ECU wire andstrip away a piece of the insulation. Using a small screwdriver or otherpointed tool, poke a hole through the bundle of exposed wire strands. Next,strip the end from the appropriate AVC-R wire, feed it through that holeand wrap it securely around the ECU wiring. Then, use a soldering ironand heat up the wire until the solder will melt on the wire (not the iron),this prevents a 'cold' solder from happening (breaks apart easily). Useelectrical tape to wrap up the splice and make sure that it can't touchany other bare wire. A small zip tie over the electrical tape ensures itdoesn't go anywhere. The best method for insulating is using heat shrinktubing and a heat gun.

7. Re-connect the ECU harness to the ECU and reinstall the ECU by reversingthe removal procedure. Make CERTAIN that you tighten the screw onthe ECU harness all the way down. Then push in both ends of the connectorto ensure a good seat in the ECU. 
 II. Install the Pressure Sensor

8. This entire procedure references picture 13. The best mountingplace for the pressure sender is on the firewall behind the balance tube.Use two self tapping screws to mount the sensor. 

9. Use the supplied 1/8" hose and secure it to the bottom of the sensor.I prefer to use zip ties to secure all vacuum connections, but the providedbrass clamps work too.

10. Determine where to tap into the vacuum system. On Carlos' install,the stock boost gauge hose was used (Inset 1, 13.). On Greg (Dallas)'and nixit (Da][as)' installs, the sensor was tapped into the vacuum hoserunning between the balance tube and the fuel dampener (Inset 2, 13.).Carlos' method is probably easier as the hose for the fuel dampener isvery short which makes it harder to deal with. Cut the selected systemvacuum hose and insert one of the small T's. Then attach the other endof the pressure sensor hose to the T. Secure all connections with zip tiesor hose clamps. 

11. Find a point on the new hose and cut it to insert the AVC-R suppliedair filter, which is the clear top/UFO looking thing. (Circled in 13.).Again secure the connections with zip ties or hose clamps. These tend tofail over time, if problems arise later, this is the first item to checkfor leaks.

12. Connect the sensor into the wiring harness. From the hole in thefender wall by the battery (6.), run the sensor connector aroundthe back of the battery compartment along the firewall and secure it invarious places with zip ties. Be SURE to not let the harness hang closeto the plenum or other part of the rear of the engine that will get veryhot. Disconnect the stock boost solenoid electrical connectors. There isone on each side of the engine. The easiest way to spot them is they arerectangular black connectors... everything else is grey. (14.) (15.)
  III. Install the Solenoid and All Vacuum Hoses

13. Remove the throttle body hoses. These are the big black hoses inthe front of the engine. I recommend marking them if the factory coloredpaint dots are worn off or keep track of them to know which side is upand what hose belongs where. A good idea is mark the hoses from left toright as 1,2,3 and 4. This will only save headache later if done now. Oncethe hoses are removed stuff the opening with some shop towels to avoidanything falling inside. This is a good time to do a throttlebody cleaning. 

14. Remove the center panel (4 x 10 mm). On '90 models there may onlybe 2 bolts. 
Depending on where the solenoid will be mounted (see next item) theintake might need to be removed. This entire procedure assumes a cone intakeis installed. To remove it, first release the mass airflow sensor connectionwhich is the black box just above the cone part of the intake. Unscrewthe filter from the shield, if it's connected. This is located on the endof the filter. Loosen the two hose clamps on each end of the larger rubberT using a flathead screwdriver or 8 mm socket and pull the entire intakeassembly out. Stuff rags in the remaining openings to make sure nothingfalls into the intake tracting.

15. There are several different mounting places for the solenoid. Picka favorite. On Greg's Z it is mounted directly against the front bumper.On Carlos' Z it's mounted on the driver's side behind the POP charger.On nixit's Z (displayed in the images) it is mounted on the passenger sideheadlight wall near the bumper. Things to consider for placement: Makesure the vacuum hoses can't be interfered with by the auxiliary fan. Ifplanning to install a dual POP charger later, put the solenoid where itwon't have to move again.

16. If mounting the solenoid directly on the back of the bumper, thecarbide drill bits are needed to drill through the steel. Otherwise, normaldrill bits can be used. Get the rectangular black rubber 'cushion' outof the AVC-R bag of parts and use it as a template to drill your holes.There are four screws but two should be plenty. Drill the holes, then securethe solenoid in place with the screws. Make sure to put the rubber 'cushion'between the solenoid and the mounting point. Nixit's installation isshown in (16.).

17. Thread the electrical harness for the solenoid from the batterycompartment forward to the center panel area. There are several pointsalong the way to zip tie it down to make the installation neat. Poke itthrough an opening by the radiator on the passenger side. (17.)Connect the harness to the solenoid.

18. Disconnect the stock boost hose underneath the INTAKE pipeon each side of the engine. This is the pipe connecting up directly tothe throttle bodies. (passenger side 18.) The yellow lines indicatewhere the hose actually connects underneath the hard pipe. (driver side19.) points out the correct hose.

NOTE: On the passenger side, make SURE to remove the correct hose.The stock recirculation valve hose connects to the other hard pipe on thepassenger side. The line in question is closest to the radiator.

If boost jets were installed, they will be in the ends of these twohoses. If they're close to the end, use a pair of needle nose pliers tosqueeze the hose behind the jet and work it forward and out of the hose.or cut the hose behind the boost jet.

19. The easiest way to install the AVC-R is to simplyconnect new hose to the ends of these boost hoses which go down to thewastegate actuators. By disconnecting the stock solenoids earlier, it effectivelykills the stock boost control system. However, contrary to what many peoplebelieve, there ARE stock boost jets installed at the other end ofthese hoses (near the stock actuators). By leaving this hose in place thecar will run slightly higher 'natural' boost, i.e. when the AVC-R is totallyoff, it will still be able to run about 9 PSI. With these hoses completelyremoved and replaced by new hose, it will run the correct 'natural' boostof 7 PSI with the controller turned off.

20. Greg's installation completely replaced the hose all the way tothe wastegate. The main reason this was done is because he was alreadydown in the engine replacing the valve covers and plenum. Both Carlos andnixit used the existing hose because it's a lot less work. If choosingto replace the entire hose, remove the hard pipes running alongside theengine to get to the other end of the hose. There is a T down there connectingthe hose to the wastegate actuator and the stock boost cut solenoid. Connectnew hose in at this point and cap off the stock solenoid with a vacuumcap. Sorry, no pics of this procedure as Greg didn't have the digital camerawhen he did the work on his car.

21. Connect the ¼" hose to the output where the stock boost wasconnected on t he hard pipe up front and use the clamps provided with theAVC-R kit or zip tie them down. Run through the headlights around pastthe center panel and back onto the other side. Yes, this is a loop!

NOTE: Since the hose has to loop back on itself to go to thefront of the car, take care that you don't get a tight crimp in it. Also,be careful on the passenger side not to end up with an excess of hose inthat area near the alternator pulley.

22. Now connect a ¼" barrel connector to the stock boost hosefor both the driver and passenger side and clamp or zip tie them down aswell. Run another piece of new ¼" hose from one barrel, throughthe headlight, center panel area, headlight and connect it to the otherbarrel connector on the other stock hose. Loop #2. Clamp or zip tie everythingdown.

23. Tie the solenoid into these two loops. Split each loop in the middleto make an equal length on each side. Insert a ¼" T connector. Cutan appropriate length of hose and run from the solenoid to the T. Connectthe COM side of the solenoid to the loop that goes to the wastegates. Connectthe NO side to the loop that is connected to the front hard pipes (intakeside). Clamp or zip tie all connections. Finally, secure the hose to variousparts of the car (frame walls, auxiliary fan, etc.) with zip ties to keepthe hoses secure. Take care, if necessary, that the hoses cannot come incontact with the opening in the auxiliary fan. Pictures 20. &21. show different approaches for the hose connections and solenoidplacement.

NOTE: Picture (21.) was taken before the install was finished.Do not leave loops in your vacuum hose as is shown in the picture. Afterthe picture was taken we pulled the rest of the hose through and got ridof the loops. Also, the T's in Nixit's install are closer to the passengerside so they wouldn't lay over the cone intake. However, the length ofhose is still the same to the passenger and driver's side. We just allowedmore hose on the passenger side that is not seen.

24. Remove the rags from the intake tracting. Reinstall the intake ifit had to be removed. Reinstall the throttle body hoses.
 IV. Install and Connect the Display Unit

25. This part is very subjective and just depends on personal preference.Greg (Dallas) installed it using the supplied bracket on the dashboardabove the center console. Carlos installed it in the second DIN slot ofthe center console and nixit's is installed in the glove box. Picture (22.)shows a couple of options.
 V. Set up the AVC-R parameters

26. Reinstall the battery and connect the terminals. Reinstall the trimpiece above it.

27. Start the engine. Go to the engine bay and listen for leaks, locateany and clamp them down tighter.

28. Enter the monitor section of the AVC-R and see if it reports a goodthrottle position (surge the engine to check), a good boost pressure (shouldbe about 1 Bar), speed should be zero as the car is not moving, and RPMshould be very close to what the dash reads.

29. There's been quite a bit of debate about how this thing actuallyworks. Basically, the FIRST thing to do is go to Car Settings and do thefollowing:
Cyl: 6
Speed: 2
Throttle: rising arrow from left to right
Decide how much boost to run. If there is not an upgraded ECU installed,set the boost no higher than .8 bar (roughly 12 psi) to be safe. If thereis an upgraded ECU, and stock injectors, set it to 1 to 1.05 bar (14 -15 PSI). If there are 555 cc injectors, set it to around 1.15 - 1.2 bar(17 - 17.5 PSI).

NOTE: These are just GENERAL guidelines. Remember, too much boostwill kill the engine fast, so if deciding to run extreme amounts of boost,don't come cry to us when the motor explodes on the freeway. Basically,this means take some responsibility for your actions, because we won't.

30. The AVC-R has three setting modes, A, B, and OFF so there are twodifferent boost settings. Choose one of them and set the base boost levelas desired. What actually controls the amount of boost is the duty cycle,not the boost setting. For 1 bar, try starting around 58%. Higher percentages= higher boost.

31. It is a good idea to find out what the 'natural' boost is with thesystem off. Set the AVC-R to OFF (hit the left arrow in the selection mode).Then go to the boost monitor screen. Find a stretch of deserted road andmake a wide open run in 3rd or 4th gear (4th goes to ~126 MPH). The boostmonitor screen should tell what peak boost was. It should be around 0.5- 0.65 bar (7 - 9 psi). This will show what the car will boost with noboost controller at all (Good to know). Put the AVC-R in the desired boostmode (A or B), get into 3rd or 4th gear again, and go full throttle again.If it boosts over your target amount, reduce the duty cycle and try again.If it boosts under, raise the duty cycle. 

32. Once it boosts correctly, make 2 more runs in succession (this meanswide open throttle). My understanding from LRD VDR and others is this triggersthe AVC-R into self learning mode which is supposedly a 'good thing'. Goback to the boost setting screen and if the duty cycle displays '***' thenit is in self learning mode and you're good to go.

Greg (Dallas)
Carlos Ramirez

Other Credits:
Greg:
Thanks to Kyle @ SGP who sold me my AVC-R and gave me the first introductionto it when I installed it on my car.
Thanks to LRD VDR who has helped me understand it a bit more than Idid before.
Thanks to nixit (Da][as) who was a willing guinea pig for my secondinstall :-)

Carlos:
I like to give credit to Sam from http://www.jspec.com/who sold me the AVC-R,
to Gyro from DSP Racing who helped me with some of AVC-R settings,
to Orion (John) from TT.NET who helped me with various questions, and
to Tom Bullinger who's web site I used as reference in the installationprocess (http://www.frontiernet.net/~tomb/BoostController.html) 

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