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Thread: How-To Control Boost with the Gm 3 port solenod

  1. #1
    Join Date
    Nov 2009
    Chico, CA (Nor Cal)

    Default How-To Control Boost using the stock ECU and a Gm 3 port boost solenod

    DISCLAIMER - This mod will change boost charateriscs drasticallly. Do at your own risk.

    BIG THANKS TO razorlab aka Bryan@GST, Malibu Jack, mrfred, jcsbanks, and anybody else that has helped in the development of ECU controlled boost.

    You will need:

    3/8 rachet
    10mm socket
    phillips screwdriver
    regular (flat) screwdriver
    regular pliars
    needle nose pliars
    soldering gun
    heat gun

    From the store(s):

    5/32 (4mm) vaccum hose (3-4 ft)
    heat shrink
    10 ohm 1 watt resistor

    From GM dealer or online:

    *** All prices here are old and wrong. I will update it shortly. Prices now are around 50 for solenoid and 20-30 for pigtail***

    Got it from Rock Auto (
    GM 3 port: 12.69. AC Delco part number 214-474.
    GM pigtails for 15.64. AC Delco part number PT 374.

    GM boost solenoid, GM Part # 1997152
    Pigtails, GM Part # 12102747

    Total at the dealer was around 50$

    Step 1

    You need to solder the resistor inline on one of the wire on the pigtails.

    **Update - the subject of the resistor is kinda up for debate. You can use the 10ohm 1 watt, as specified in this how-to, a different resistor (look up MRFREDS thread about testing Boost solenoids on EvoM for more info), or you can run without a resistor. There is a good amount of cars that have been running for multi years with no resistor



    Step 2

    Cover the connection with heat shrink


    Step 3

    Remover air filer and stock boost control lines and solenoid. Use the last how to for info on this.

    Step 4

    By now you have the stuff removed. Connect the pigtail to the stock wire. I cut off the solenoid and connected with the butt connectors that were included with the pigtails. There is also alternatives, you could solder it and you could also use in-line taps, so you dont have to cut the stock plug off.

    Last edited by Evo_Kid; 11-25-2009 at 09:21 AM.

  2. #2
    Join Date
    Nov 2009
    Chico, CA (Nor Cal)


    Step 5

    Now you have to mount the solenoid. The first way I mounted it DID NOT work with the stock intake, but will work with an aftermarket intake.


    This way will work with the stock airbox.


    Step 6

    Now you have to run the vacuum lines. You WONT NEED ANY brass restrictors/boost pills or tee's. Here is a pic of the GM BCS. Pretty self explanatory. Port "A" goes to the wastegate. Port "B" goes to the lil port on the bottom of the stock intake (If using a aftermarket intake, the line can just VTA, if there is no lil port on the aftermarket intake). Port "C" goes to the the nipple on the turbo/turbo outlet pipe (or other source of vac/boost)

    Last edited by Evo_Kid; 11-25-2009 at 09:42 AM.

  3. #3
    Join Date
    Nov 2009
    Chico, CA (Nor Cal)



    Step 7 - Tuning
    The following maps will need to be changed for basic boost control

    Max WGDG/Basline WGDC (NOTE: map will be titled MAX WGDC or Baseline WGDC, based on what definitions your using. They are the same map.)

    Boost Desired Engine Load

    Boost Control Load Offset

    Turbo Boost Error Correction

    Boost Limit - This is the famous "Boost/fuel Cut". Set this about 20 higher then your max load.

    ***When taking the car out for the first test drive, roll on to boost SLOWLY and constantly monitor boost. If it starts to boost more then a safe amount for your octane and tune, LET OFF THE GAS.

    Zero out the right side of the "Turbo Boost Error Correction" map. (keep a copy of the stock settings somewhere)

    Then use the "Max WGDG/Basline WGDC" to get your desired boost curve in 3rd gear.

    **Here is an example
    RPM - WG duty
    2000 - 70
    2500 - 60
    3000 - 50
    3500 - 50
    4000 - 50
    4500 - 50
    5000 - 55
    5500 - 55
    6000 - 60
    6500 - 65
    7000 - 70

    After you have your desired boost curve, log your load (preferable 2byte load) in 3rd gear from 2500-7500RPM.

    Set "Boost Control Load Offset" and the "Boost Desired Engine Load" so when they are added together, they add up to the load in your log (@ the same RPM point). ie if you logged 240 load @ 3500RPM, then the "Boost Control Load Offset" would be 100 and the "Boost Desired Engine Load" would be 140 @ 3500RPM.

    After you have your "Boost Desired Engine Load" completely filled out, using your logs for load amounts, then re-enter the stock setting on the right side of the "Turbo Boost Error Correction" map (Stock setting can work, but you may have to tune this map)

    It will take some tuning to get everything perfect. Log Load, boost, WGDC, Load Error and WGDC Correction and make correctiosn based on those.

    Also, here is a great description on how the error correction work. Thanks mrfred
    *BDEL=Boost Desired Engine Load

    Quote Originally Posted by mrfred View Post
    The "Max WGDC" table is poorly named. It should be called "Baseline WGDC" table. When you are cruising, the car is at 0% WGDC (at least that's what EvoScan says), and when you stomp on the gas, the ECU looks at the engine RPM, then goes to the Baseline WGDC table, reads the WGDC number, and applies that value to the BCS. At that point, the ECU then starts comparing the actual load to the target load (BDEL + boost offset) about once every 0.4 seconds. If the actual load matches the target load, then the ECU continues to follow the WGDC value (vs RPM) in the baseline WGDC table. However, if the ECU sees a discrepancy between actual and target load, then it can/will apply a correction to the WGDC. The amount of correction depends on the values in the boost error correction table. The correction is simply to raise or lower the entire Baseline WGDC curve. So after the correction is applied, the ECU follows the raised/lowered curve. It checks again 0.4 seconds later, and if necessary, raises or lowers the curve again. This is why the correction table isn't a function of RPM. The graph shows the behavior well. The blue arrows show when corrections are made, and its apparent that the ECU is simply raising/lowering the baseline WGDC curve.

    Last edited by Evo_Kid; 11-25-2009 at 09:24 AM.

  4. #4
    Join Date
    Nov 2009
    Chico, CA (Nor Cal)


    Here are link to "mods" that can be done to make ECU boost better and easier to tune

    Fine tuning Load based boost control to prevent weather based boost variation by mrfred

    Direct ECU boost control by mrfred
    Last edited by Evo_Kid; 11-25-2009 at 07:28 AM.

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