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Thread: Why does no one care about WOT TCC Lockup?

  1. #1
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    Why does no one care about WOT TCC Lockup?

    I was going to ask the question on the thread below, but most everyone is not concerned about WOT, especially since the 8L90 only has shuddering problems at very light throttle (which I believe are 100% fixed by the new Mobil 1 fluid).

    Even though you know for sure you are commanding lockup at WOT, the TCM ignores you. My Camaro with the 8L90 sees about 150-200 rpms of slip at WOT, I don't know how to translate this to a power, but im sure it would add up to 10 maybe 20 or 30 or 40 rwhp at the wheels of wasted energy that should be put into kinetic energy to move the car forward but is instead lost to useless heat.

    The same problem was present on the Duramax on the Allison and the Allison TCM had a hidden table that inhibited lockup past a certain threshold of TC slip, and with increased power you would always run over this threshold. I wonder if that's the case here too?

    Earlier before I swapped in my cam and heads im pretty sure I remember seeing full lockup (0 slip rpm) at WOT, although it still didn't do it instantly like commanded, it would still take until the very top of 2nd before it fully lock with zero slip. Now its just completely ignoring it.

    I do have the stock torque converter and I have the latest Mobil1 fluid that fixes the shudder. The main thing is with everyone so obsessed with every last bit of HP they can get, why does no one care about the wasted power going through and unlocked TCC at WOT. I understand not locking it in 1st gear since you can use it to stall and I can also understand unlocking it during WOT shifts, but it is completely baffling to me why some people think it should be unlocked at WOT.
    Last edited by cmitchell17; 07-14-2020 at 11:45 PM.

  2. #2
    I care and am here to try and figure out a fix. Here is my post from another forum.

    Anyone have luck controlling the tcc lock up pressure? The logged pressure doesn’t match the apply ramp pressure at all and upping the pressure in the apply ramp and max pressure tables doesn’t seem to have any effect.

    My issue is I want to use my lock up at wot. If I command it with hp tuners bidirectional control it reads something like 594psi and will hold any power I have thrown at it. Letting the ecm control the pressure it rarely reads over 100psi and won’t hold much power at all.

    I have not messed with regulator gain or regulator offset. Anyone know what those do?
    2017 camaro ss a8 with low mount twins

  3. #3
    Senior Tuner kingtal0n's Avatar
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    I doubt this will help. But its just a thought. On the 4l60e and 700R4 and 4l80e the TCC is controlled by a lockup solenoid, and apply pressure afaik is based on duty cycle. So if you just wire it directly to 12v it goes 99.9% duty cycle manually and walaa its fully locked as hard as it can be. Not sure that will work on your trans but you might be able to use a similar tactic since... after all it is just a hydraulic device... you can usually over-ride electronics by manually activating something or drilling a hole or something like that.

  4. #4
    Quote Originally Posted by parish8 View Post
    I care and am here to try and figure out a fix. Here is my post from another forum.

    Anyone have luck controlling the tcc lock up pressure? The logged pressure doesn’t match the apply ramp pressure at all and upping the pressure in the apply ramp and max pressure tables doesn’t seem to have any effect.

    My issue is I want to use my lock up at wot. If I command it with hp tuners bidirectional control it reads something like 594psi and will hold any power I have thrown at it. Letting the ecm control the pressure it rarely reads over 100psi and won’t hold much power at all.

    I have not messed with regulator gain or regulator offset. Anyone know what those do?
    Haha thank you Parish, I have messed with all of those parameters too many times and notice absolutely no difference. And good idea about trying to use bi-directional controls, at least we can use these as a last resort.

    Also does anyone know a general equation for converter efficiency? or a way we can calculate the heat power lost as a function of slip RPM? Unfortunately there is not much published or standardized info for torque converters, even published SAE papers don't have any info on them. It seems like it was something that was well thought out and explored in the 50s (I think some Buicks had variable pitch stators in series instead of gear in their transmissions) but here lately no more development has been put into them.

  5. #5
    Quote Originally Posted by kingtal0n View Post
    I doubt this will help. But its just a thought. On the 4l60e and 700R4 and 4l80e the TCC is controlled by a lockup solenoid, and apply pressure afaik is based on duty cycle. So if you just wire it directly to 12v it goes 99.9% duty cycle manually and walaa its fully locked as hard as it can be. Not sure that will work on your trans but you might be able to use a similar tactic since... after all it is just a hydraulic device... you can usually over-ride electronics by manually activating something or drilling a hole or something like that.
    I believe you would burn up the solenoid if you just straight up ground it, I think you would need to build a stand alone PWM driver. This was the case with the Allison TCC in the duramax you would burn it up if you tried to ground it, but im not an electrical engineer.

  6. #6
    Quote Originally Posted by cmitchell17a View Post
    I believe you would burn up the solenoid if you just straight up ground it, I think you would need to build a stand alone PWM driver. This was the case with the Allison TCC in the duramax you would burn it up if you tried to ground it, but im not an electrical engineer.
    I am just looking to over ride it down the track. Maybe 6 seconds at a time. We’re they locking it up for long periods of time?

    I could set up a pwm or variable voltage control pretty easy but a direct on would be easier. It is nice there have an external controller so you don’t have to pull the pan to try things.

    I did try some tuning one last time last night. The gain and offset seem to do nothing to the reported pressure or amount of slip. Playing with the apply ramp seems to have got me a little more consistent pressure. It now goes to 113psi reported and pretty much stays there. That is an improvement but not enough pressure to hold at wot and I only have ~600hp right now. This is a circle d triple disk converter that holds solid when commanded with bidirectional control.
    2017 camaro ss a8 with low mount twins

  7. #7
    Yes I believe they were at least the length of a sled pull and a 1/4 mile run. What about trying to hack the bi-directional function to come on as needed I don't see any other limiters when it is active, I feel like if someone made a driver they would run into all kinds of other issues?

    I still kind of think the best course of action would be to expose the proper parameters in the TCM to get lockup to work correctly.

    Also this is kind of ancedotal by me but I swear I remember when stock the torque converter locking up better? It still wouldn't lock when commanded WOT MPH hit in first gear, but it would eventually at the end of second.
    Last edited by cmitchell17a; 07-17-2020 at 09:58 AM.

  8. #8
    The whole bidirectional control thing is sweet but it seems slow and not 100% consistent. Also I have no idea how you would do that. I currently have a stand beside ecm that runs a pile of stuff. I could set up a lock up output in a number of different ways and it would be consistent and built into the car. Just not sure about it going into limp mode.

    It would be great if they uncovered all the tables.
    2017 camaro ss a8 with low mount twins

  9. #9
    Quote Originally Posted by parish8 View Post
    The whole bidirectional control thing is sweet but it seems slow and not 100% consistent. Also I have no idea how you would do that. I currently have a stand beside ecm that runs a pile of stuff. I could set up a lock up output in a number of different ways and it would be consistent and built into the car. Just not sure about it going into limp mode.

    It would be great if they uncovered all the tables.


    Im curious about your apply ramp changes. When i messed with them i got locking unlocking and locking over
    and over. The only thing that even showed a hint of inprovement was setting my gain to 0. Still varies around starting at about 45psi.

  10. #10
    Seems like its going to take some high end racing teams to push HP Tuners to uncover the right tables. The Duramax guys got EFI Live to do it for the Allison TCMs they just need to realize the wasted potential by having the TC not lockup at WOT.

  11. #11
    Senior Tuner kingtal0n's Avatar
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    Quote Originally Posted by cmitchell17a View Post
    I believe you would burn up the solenoid if you just straight up ground it, I think you would need to build a stand alone PWM driver. This was the case with the Allison TCC in the duramax you would burn it up if you tried to ground it, but im not an electrical engineer.

    I understand why you would think that. However the ECU is able to command 99% Duty cycle which is a straight voltage DC current (99% = 100%). There is no "off" time for PWM when fully commanded *ON* to 99% or 100%. The same thing is seen in fuel pumps, using PWM to limit current but when it goes 99% or 100% That is straight up DC power.

  12. #12
    Senior Tuner kingtal0n's Avatar
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    Quote Originally Posted by cmitchell17a View Post
    Seems like its going to take some high end racing teams to push HP Tuners to uncover the right tables. The Duramax guys got EFI Live to do it for the Allison TCMs they just need to realize the wasted potential by having the TC not lockup at WOT.
    I asked a converter manufacturer a long time ago (Dave at Yank) And I believe he told me that the car would go faster with the converter unlocked. maybe not peak MPH but faster in the 1/4 mile ET. Although I think it depends on the exact nature of the setup. You might want to check with the converter manufacturer or try both. Don't just assume one is better.

  13. #13
    Senior Tuner mbray01's Avatar
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    Quote Originally Posted by kingtal0n View Post
    i asked a converter manufacturer a long time ago (dave at yank) and i believe he told me that the car would go faster with the converter unlocked. Maybe not peak mph but faster in the 1/4 mile et. Although i think it depends on the exact nature of the setup. You might want to check with the converter manufacturer or try both. Don't just assume one is better.
    depends on power output

    stock cube naturally aspirated, yes

    big cube, or power adders, and you start getting to a point where locking the converter brings efficiency back, and it will mph better locked

    how you control lock up is all in what you are doing!!!!
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  14. #14
    Quote Originally Posted by mbray01 View Post
    depends on power output

    stock cube naturally aspirated, yes

    big cube, or power adders, and you start getting to a point where locking the converter brings efficiency back, and it will mph better locked

    how you control lock up is all in what you are doing!!!!
    Can you elaborate a little more? Are you saying there is a way to make the TCM do it with what we have available? I'm pretty sure I remember the converter locking at WOT back when I was stock.

    There is definitely a lot of things going on that I don't understand in terms of the way the friction modifiers in the fluid are designed. For example, why does it shudder at low speed and it causes problems and eventually destroy the clutch material, but it can be at WOT with full torque at way higher relative slip rates and the TCM with stock tuning allows this, and also no shudder feeling is felt. The "controlled" slip is definitely very unstable and black magic filled.

    My guess is at peak slippage at WOT we could be losing 50hp through the converter? That's a lot of power. The only time I think it should be unlocked is in first gear below 3000rpm and when it shifts and downshifts to help absorb tie ups and torque reversals and spikes from the transmission shifting.

  15. #15
    Senior Tuner mbray01's Avatar
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    with the programming we have, you most certainly can make the converter do whatever you want.

    on the 8 speeds, n/a, stock displacement, i leave the converter unlocked until 6th gear, it "feels" better this way, no lugging, surging etc. it drives more natural, like most customers are accustomed to from previous models. WOT i do not lock the converter at all. it will mph better with it unlocked. Proven it many times. On the dyno, I lock it wot, but that is so I get a more accurate reading from the machine.

    the "shudder" is controlled with a couple tables, mostly apply ramp rates. if you look at this main table you will see your questions answered here on why it doesnt shutter wot. as torque is increased, so is pressure. The issue with the converters is many sided. more than just the fluid, its a cheap apply disk, and not enough pressure at cruise.

    in most instances the shutter can be eliminated with proper tuning, if done before it has done any actual damage.
    Michael Bray
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  16. #16
    Quote Originally Posted by mbray01 View Post
    with the programming we have, you most certainly can make the converter do whatever you want.

    on the 8 speeds, n/a, stock displacement, i leave the converter unlocked until 6th gear, it "feels" better this way, no lugging, surging etc. it drives more natural, like most customers are accustomed to from previous models. WOT i do not lock the converter at all. it will mph better with it unlocked. Proven it many times. On the dyno, I lock it wot, but that is so I get a more accurate reading from the machine.

    the "shudder" is controlled with a couple tables, mostly apply ramp rates. if you look at this main table you will see your questions answered here on why it doesnt shutter wot. as torque is increased, so is pressure. The issue with the converters is many sided. more than just the fluid, its a cheap apply disk, and not enough pressure at cruise.

    in most instances the shutter can be eliminated with proper tuning, if done before it has done any actual damage.

    Could you please elaborate on the function of the apply ramp table. What are the pressure numbers in relation to? I just want my converter to lock at a solid number and hold that pressure but no matter what i do it at light load i have a very low line pressure that gradually comes in with more throttle. Even when setting my tcc apply ramp to offset pressure across the board. I feel i am not understanding the proper usage of the ramp table. Thanks

  17. #17
    Senior Tuner mbray01's Avatar
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    the apply pressure ramp table is how much pressure is applied, or released to achieve the desired slip speed

    if you are commanding a slip speed of 20rpms, then the zero column is 20 rpms, if its slipping 25 rpms, it will apply the pressure from the 5 rpm column to bring it back to 20, if its slipping 15 rpms it will release the pressure in the -5 rpm column to allow it to slip to 20 rpms

    now if your commanding zero slip, the the table directly correlates to the slip rpm in the columns

    this table directly affects how fast, it locks, it directly correlates to lock up feel(how harsh)
    Michael Bray
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  18. #18
    ok so while that makes sense I still feel lost on adjusting this table. i just want the most pressure i can get at cruise. this is what i have so far. i just adjusted the ramp table and haven't tried it in the truck yet so im about to go do that. so please flame away if i totally botched it lol.
    Attached Files Attached Files

  19. #19
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    You don't think if we lock, then unlock for the shift, then relock we would be faster? Do you know how much power is lost at the torque converter at WOT? I see on average about 200 rpms of slip at WOT, I don't know of a way to equate that slip to efficiency loss, there is not a lot of scientific documentation on torque converters unfortunately.

  20. #20
    I am able to get some control of the tcc pressure. Just not as much as is needed to get it to completely lock up. I am also seeing about 200rpm of slip at my current power level(~600hp). That goes up with more power. When commanded with bidirectional control I see zero slip.

    The apply ramp only goes to 149psi so even if the reported tcc pressure went to 149psi it still may not hold. Currently the most I see is 113psi reported. With bidirectional control it reports 594psi and holds solid.

    In past vehicles I have seen small improvements in et and significant improvements in mph locking up the converter. In turbo cars getting a converter to slip enough to let you get to 4000rpm on the line and then all the sudden hold back lots of tq without flashing too far past peek tq is tuff.
    2017 camaro ss a8 with low mount twins