Results 1 to 19 of 19

Thread: Max Pressure and Base Line Pressure

  1. #1
    Tuning Addict WS6FirebirdTA00's Avatar
    Join Date
    Jan 2005
    Location
    Concord, NC
    Posts
    8,093

    Max Pressure and Base Line Pressure

    I have been trying to search with mixed results and a lot of old posts showing up, so time to make my own thread.

    I am trying to understand max pressure setting vs. the line pressure set point.

    For example, my stock tune has 110 PSI as max pressure. In 1st gear, 200 Nm of torque is 110.x PSI.

    So, does that mean as torque increases the pressure will never exceed that 110 PSI?


    I read a lot, saw Chris post a good bit of detail on the 6 speed several years back. I am curious to see what guys are doing with the 8 speeds (especially trucks) with line pressure. I see some guys increasing line pressure, but if you don't touch the max pressure, at high loads it will basically do nothing from what I understand. Based on some reading, I tried mine at 235 PSIG, but backed it down to 125 PSI until I can better understand. I know what Chris said was that was similar to the water valve in your house. It set the max pressure that could be obtained, but did not mean it would actually go to that pressure. I also read where some trouble codes will force max line pressure, so that was a big concern too.

    I adjusted some of the excessively high shift times and went up 1 point in the inertia tables. I am trying to avoid the pressure table changes until I understand the max vs base. Really, can I leave the pressures stock and just live off the inertia changes. My main goal is to ensure the reduce shift time is properly balanced with line pressure.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  2. #2
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
    Location
    Regina, Sask.
    Posts
    4,213
    I never touch the max pressure or inertia tables. I firm up the shifts with the base shift pressure tables & the upshift desired shift times. But can you post your stock tune? As I've only tuned the 2015-16 8 speeds. Maybe there are some differences in the 2017-18 8 speeds?

    Russ Kemp

  3. #3
    Tuning Addict WS6FirebirdTA00's Avatar
    Join Date
    Jan 2005
    Location
    Concord, NC
    Posts
    8,093
    Here is the stock TCM tune, read it separately, sorry lol
    Last edited by WS6FirebirdTA00; 01-21-2019 at 07:35 PM.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  4. #4
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
    Location
    Regina, Sask.
    Posts
    4,213
    Ok, the 2018 is basically the same as the 2016 trans. I add 10 psi to the 221 lb-ft column & 40 psi to the 295-590 lb-ft columns of the base shift pressure TCC on & off tables.

    On the 8 speed trans, I disable the upshift & power downshift torque management. But leave the CT downshift enabled.

    Then I lower the Desired Shift Time > Upshift Normal by 10% at a time until the shift firmness is to your preference, do the same for the Upshift Pattern A (Tow/Haul). I usually leave the stock shift times up to 1700 RPM.

    I also set the WOT shift RPM to 5800.

    Russ Kemp

  5. #5
    Tuning Addict WS6FirebirdTA00's Avatar
    Join Date
    Jan 2005
    Location
    Concord, NC
    Posts
    8,093
    Thanks Russ, great info!

    So if the base line pressure exceeds the max line pressure, would it not be clipped? That is where I am getting confused.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  6. #6
    Tuning Addict WS6FirebirdTA00's Avatar
    Join Date
    Jan 2005
    Location
    Concord, NC
    Posts
    8,093
    Would also be interested to see what you think about this:

    https://forum.hptuners.com/showthrea...-Normal-or-Bug
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  7. #7
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
    Location
    Regina, Sask.
    Posts
    4,213
    Quote Originally Posted by WS6FirebirdTA00 View Post
    Thanks Russ, great info!

    So if the base line pressure exceeds the max line pressure, would it not be clipped? That is where I am getting confused.
    I used to believe that, but I can make the shifts violent without touching the Max Pressure table. I'm thinking the Max Pressure table is the max pressure on top of the Base Shift pressure that is allowed.

    In fact, on some 6 speeds, changing the Max Pressure tables caused the trans to fall out of gear intermittently. Returning the Max Pressure tables back to stock was the fix every time.

    Russ Kemp






  8. #8
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
    Location
    Regina, Sask.
    Posts
    4,213
    Quote Originally Posted by WS6FirebirdTA00 View Post
    Would also be interested to see what you think about this:

    https://forum.hptuners.com/showthrea...-Normal-or-Bug
    The 2016 5.3/8 speed, has the exact shift pressures as your truck. Just set up the shift pressures as I suggested & fine tune with the shift times.

    Russ Kemp

  9. #9
    Tuning Addict WS6FirebirdTA00's Avatar
    Join Date
    Jan 2005
    Location
    Concord, NC
    Posts
    8,093
    Interesting, thanks!
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  10. #10
    Tuning Addict WS6FirebirdTA00's Avatar
    Join Date
    Jan 2005
    Location
    Concord, NC
    Posts
    8,093
    Russ - one more question - how fast do you draw the line for trucks on shift times?

    I am around 0.30-0.33 sec on 1-2 and 2-3 shifts. It feels alright, could be a little snappier, but I don't want to push it too far. Just looking for some feedback based on success
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  11. #11
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
    Location
    Regina, Sask.
    Posts
    4,213
    Once I get the part throttle/low RPM shift firmness right, then I keep lowering the 4800-6500 RPM columns by 10% at a time. I have .152 in the bottom right of the 1-2 shift & .209 in the bottom right of the 2-3 shift. Did you disable the upshift torque management?

    Russ Kemp

  12. #12
    Tuning Addict WS6FirebirdTA00's Avatar
    Join Date
    Jan 2005
    Location
    Concord, NC
    Posts
    8,093
    I have TM on for now, little hesitant to remove that.

    What am I risking disabling that and power downshift?
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  13. #13
    WS6FirebirdTA00 I posted looking for an answer for the exact same question. Have you had a chance to try any of this? My Max line pressure is at 200psi right now. I am going to take it back to stock setting and increase oncoming presets even more and lower the shift times a little more. I was afraid of going to far below .3 but I won?t know until I try. I kept raising the max pressure setting thinking that it was the limiting factor on line pressure.

  14. #14
    Tuning Addict WS6FirebirdTA00's Avatar
    Join Date
    Jan 2005
    Location
    Concord, NC
    Posts
    8,093
    No clear answer unfortunately.

    From what I gather, the inertia and time settings - paired with adaptive parameters - get your final line pressure. I have made some line pressure changes that I feel were ultimately “learned out” because it didn’t meet the shift time criteria. I honestly feel the inertia table is what ultimately clips it.

    That being said, take it for what it is, my opinion lol You may see line pressure change feel right away, I wonder if it will learn out. There may be cases where the adaptation hits a limit and no longer can adjust enough to satisfy the request.

    To be honest, I am happy with how mine shifts and I didn’t mess with any line pressure tables with the exception of 3-4 because I saw some flare at time. I am not sure if it was a cold transmission and fillup time due to bleed down after long periods of not driving or what. I noticed it a lot more flare after reflash, which makes me wish I could pull the adaptive values and hardcode the baseline values. With the pressure changes I made I did get better stability in the long run. Even then, I bumped up some low values by what I consider a stupid amount - shifting flex no different. I am talking about 50% changes! Again, just me wondering and tinkering. My knowledge of autos isn’t enough to give sound advice.
    Last edited by WS6FirebirdTA00; 03-11-2020 at 07:25 PM.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  15. #15
    Thanks.

  16. #16
    Tuner
    Join Date
    Dec 2019
    Location
    Boerne, TX
    Posts
    117
    Quote Originally Posted by Russ K View Post

    On the 8 speed trans, I disable the upshift & power downshift torque management. But leave the CT downshift enabled.

    Russ Kemp
    Hi Russ,

    Are you referencing these two settings under TM? Is that a safe thing to do on a 5,500 lb truck? If it's too aggressive, how can it be tamed? enable it and start modifying the shift torque factor tables?

    TM.JPG

  17. #17
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
    Location
    Regina, Sask.
    Posts
    4,213
    That’s where I disable the upshift & downshift torque management. On some vehicles, I leave the power downshift field stock as some owners say the part throttle downshift is too harsh.

    Russ Kemp

  18. #18
    Tuner
    Join Date
    Dec 2019
    Location
    Boerne, TX
    Posts
    117
    Thanks Russ. Do you have any experience with these tables (in green below)? I changed my minimum TPS to 40% and increased minimum torque too. With these two fields it seems like the TCM needs to satisfy both to activate TM on upshifts. First, the TPS, second, the torque. Or vice versa. Just food for thought.

    TM.JPG
    Upshift TM.JPG
    Upshift TM 2.JPG

  19. #19
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
    Location
    Regina, Sask.
    Posts
    4,213
    I don't touch those tables, as I disable the upshift torque management as in post #16.

    Russ Kemp