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Thread: TIII Boost Control

  1. #1
    boostaholic
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    TIII Boost Control

    Does anyone have a firm grasp on how the boost control works on a TIII Sbec or SBECII car? There are multiple lookup tables that can be changed, the TIII boost controls is a complicated thing. I would like to understand it so I can begin to learn how to tune it. Currently I have been fiddling around with it and I can either get my car to run at waste gate pressure of 20 psi or the solenoid wont open and it will pull in excess of 30 psi causing detonation. I want to get a handle on this soon.

  2. #2
    Visit www.boostbutton.com... Turbo Mopar Contributor ShelGame's Avatar
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    Re: TIII Boost Control

    Quote Originally Posted by DoubleD View Post
    Does anyone have a firm grasp on how the boost control works on a TIII Sbec or SBECII car? There are multiple lookup tables that can be changed, the TIII boost controls is a complicated thing. I would like to understand it so I can begin to learn how to tune it. Currently I have been fiddling around with it and I can either get my car to run at waste gate pressure of 20 psi or the solenoid wont open and it will pull in excess of 30 psi causing detonation. I want to get a handle on this soon.
    Your wastegate doesn't open until 20psi? Why so high? You won't be able to control the boost any lower than the WG open pressure.

    The TIII boost control is similar to the T1; just with a more complicated spike management system.
    https://db.tt/SV7ONZpQ
    Rob Lloyd
    '89 Daytona C/S

    2.5 T1 Auto
    13.24 @ 100.5mph
    NHRA #3728 AF/S

    boostbutton.com
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  3. #3
    boostaholic
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    Re: TIII Boost Control

    Holset HE 341 turbo and waste gate can, I don't want to control it any lower, the car is decently dialed in at 20 psi. I want to be able to have the waste gate open above 20 psi. The plan is to run the stock ecu and use stock boost control for 35-40 psi. The solenoid does work because it will limit the boost when set really low, but I can get it to open and close any higher. I want to understand how the ecu decideds to actuate this solenoid.

  4. #4
    boostaholic
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    Re: TIII Boost Control

    Here's all the tables that are used in MPScan.

  5. #5
    Visit www.boostbutton.com... Turbo Mopar Contributor ShelGame's Avatar
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    Re: TIII Boost Control

    Right, those are the target lookups. Like all other cals, the lowest value from those tables is used.
    https://db.tt/SV7ONZpQ
    Rob Lloyd
    '89 Daytona C/S

    2.5 T1 Auto
    13.24 @ 100.5mph
    NHRA #3728 AF/S

    boostbutton.com
    tuning wiki

  6. #6
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    Re: TIII Boost Control

    Do you have a preference of which table to use? Thanks for this valuable info, I wonder why they choose to use so many look up tables.

  7. #7
    Visit www.boostbutton.com... Turbo Mopar Contributor ShelGame's Avatar
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    Re: TIII Boost Control

    For different conditions - coolant temp, RPM, speed, etc. You need to set them all up. The software looks at all of the tables and always chooses the lowest value from them all. If you don't want to use a specific table, just set it's points to the max. Then it will have no effect.
    https://db.tt/SV7ONZpQ
    Rob Lloyd
    '89 Daytona C/S

    2.5 T1 Auto
    13.24 @ 100.5mph
    NHRA #3728 AF/S

    boostbutton.com
    tuning wiki

  8. #8
    boostaholic
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    Re: TIII Boost Control

    I set them all high and then set the "allowedboostpartthrottle from throttle" 18.159 @ 1.0v and 20.234 @1.25v. Boost is controlled at 26 psi. Works great now!

  9. #9
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: TIII Boost Control

    Sounds like the WOT Duty Cycle needs adjusting...
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

  10. #10
    boostaholic
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    Re: TIII Boost Control

    Do you have any experience with that? Sounds like the next area of the mptune that I need to teach myself.

  11. #11
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    Re: TIII Boost Control

    I can confirm that after a couple of WOT pulls after a computer reflash that the ECU will adjust the wastegate duty cycle to maintain what ever the boost target is set to. How do I adjust the Waste Gate duty cycle to eliminate the computer having the adjust and have it correct after a flash, otherwise I have to do a couple of overboost pulls to cause the computer to adjust the duty cycle.

  12. #12
    Visit www.boostbutton.com... Turbo Mopar Contributor ShelGame's Avatar
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    Re: TIII Boost Control

    Theres a table for the WG Duty Cycle. Log what your actual DC is to maintain a given boost, and adjust the last datapoint in the WG DC table to match.
    https://db.tt/SV7ONZpQ
    Rob Lloyd
    '89 Daytona C/S

    2.5 T1 Auto
    13.24 @ 100.5mph
    NHRA #3728 AF/S

    boostbutton.com
    tuning wiki

  13. #13
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    Re: TIII Boost Control

    Rob,
    I finally have dug into the WGDC table and all the associated info and have a decent understanding how it works. How does the boost control on this car work, is the solenoid acting like a bleed not letting pressure to reach the wastegate or is it closing off pressure till a predetermined boost level is met, how does this system work? Will a higher WGDC give me a higher boost level or do I lower the WGDC in order to get the boost higher, can not get the car to boost over 25 PSI right now and the boost target is 30 PSI, as displayed on MPScan.

  14. #14
    Visit www.boostbutton.com... Turbo Mopar Contributor ShelGame's Avatar
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    Re: TIII Boost Control

    It's kind of a hybrid system. It controls the signal to the WG can (like the 2.2 T2), but with a failsafe (like the '89/90/91 2.5 T1). So, 0 WGDC = minimum boost. 100% WGDC means no boost signal to the WG can.

    The TIII also has some more 'advanced' adaptives. Like a more primitive version of the torque control the SRT4 used...
    https://db.tt/SV7ONZpQ
    Rob Lloyd
    '89 Daytona C/S

    2.5 T1 Auto
    13.24 @ 100.5mph
    NHRA #3728 AF/S

    boostbutton.com
    tuning wiki

  15. #15
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    Re: TIII Boost Control

    Got a handle on it now, stock ECU and solenoid are controlling the boost accurately above 30 PSI with 75% WGDC, no need to replace the solenoid, stock one is fine.

  16. #16
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: TIII Boost Control

    Quote Originally Posted by DoubleD View Post
    Got a handle on it now, stock ECU and solenoid are controlling the boost accurately above 30 PSI with 75% WGDC, no need to replace the solenoid, stock one is fine.
    Can you elaborate on this some? I'm having the same issues on a 91 RT with a ported head and cams, but with a S70 turbo. Got boost targets all set to 20 psi, but won't go over 14-16psi unless we pull the line off the wga, even with the WOT duty cycle at 20psi set to 100%.
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

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