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Thread: 8 Speed shift points Questions

  1. #1
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    8 Speed shift points Questions

    Dear lord what's wrong with the dudes at ZF8 Lol. Where is the to table to adjust output shaft rpm vs TPS
    So i'm tyring to make the wife a little happier and simply make her Durango shift to 1st without having to come to a full stop.
    Learning how to tune this trasmission i found the articles by Steven@ HPT where he explains the basics for tuning the 8 speed.


    ------------------------------------------- From our HPT sticky ------------------------------------------------------
    "Getting to know your ZF TCM. Sticky please for updates.

    [​IMG] Originally Posted by Steven@HPTuners [​IMG]
    The ZF8 is used in many applications and when we originally added it last year, we tried to make it a little more Dodge specific, but quickly realized this was not an easy effort, especially as we add more manufacturers.
    The ZF8 is better thought of as its own controller by itself and not a "Dodge" controller, because that's what it really is.

    4WD Low are used only during 4WD Low applications, but the Hellcat does not ever use these. The reason you still see the tables is the operating system used by the Hellcat is not unique to the Hellcat, other applications that do have 4WD Low (the trucks) also have the same operating system. Because we define things by operating system, you'll see them in all applications, including unused ones.

    Normal, Perf, Sport, Max: these are shift strategies. Which one is used by which mode is actually quite a cluster and we don't have an easy way to show which is which, so its being added as a loggable parameter in Beta, under "Clutch Shift Type". For example, on a Hellcat, Normal trans mode in Drive, uses "Normal". But put it into Manual Mode with Normal Trans still selected, and now it uses Perf tables.

    It's also considered a "use the highest below this". For example, if your current type is Sport, but the table set only has Normal and Perf, it uses Perf. The idea being that Normal -> Perf -> Sport -> Max have increasing levels of shift speed and feedback.


    As to the "Normal, Normal Perf, Sport, Sport Perf, Track" shift schedules, I've started to relabel some of this to better correspond to whats happening. Basically depending on your actual selected trans mode, how aggressive you're currently driving, and your perceived hill grade, the shift tables are designed to get more or less aggressive.

    To explain this, I'll use the ZF9 as an example as I believe we will move everything to be more like it to better indicate this.

    Attachment 81473
    First, we decide our Aggression level. To do this, we need to know our current Shift Situation (which is basically your trans shift mode. In the Hellcat, Normal, Sport, Track, Valet, etc all have their own "situation"). This is loggable.

    The situation automatically puts you into a certain range of "Driver Type". 0 being the least aggressive driver, up to a max of 14 being the most aggressive driver.
    As well, there's a constant "counter" running thats basically an indication of the current aggression of your actions. Some situations may have a range, for example, 20 to 200 for your aggression counter. As you move up the counter, you start moving into higher driver types.

    Finally, your driver type is mapped into an "Aggression". For example, we have lower type = 0, upper type = 4, lower aggression = 0, upper aggression = 1, this means that driver type 0 is aggression 0, driver type 4 is aggression 1. In between driver types are blended between the various aggressions.

    For Dodge, we simply named the aggression modes. Normal = 0, Normal Perf = 1, Sport = 2, Sport Perf = 3, Track = 4. However, the Shift Pattern Aggression Mapping for the Hellcat actually has the highest aggression being 3, Sport Perf. I.e. the high part of the table for driver types 9-14 actually blends from 4 to 3 aggression.


    Now once you know your aggression, you'll notice there are 5 tables for that given aggression. These correspond to your accel factor / hill grade essentially. On the ZF9, its labelled by the Shift ID youd see if you logged Shift ID, on the ZF8 we still have it labeled "Normal 0, Normal 1, Normal 2, etc."
    Attachment 81474

    But, by using the "Accel Factor" tables, you can see what your final factor will be. Unfortunately this isnt straight forward to describe as the inputs are based on measured G-Forces, estimated road grade, etc. But the gist is Accel Factor 0 is typically when you're going downhill, Accel Factor 1 is normal, 2,3,4 are proceeding amounts of aggression (heavy Gs) or uphill orientation. You can log Accel Factor directly as well to help actually know what you're currently in!


    These are the standard, aggression based maps. As well, the ZF8/9 have 75 MORE maps for various other conditions, though usually not all of them are used. I've placed these in a non-aggression section, and it corresponds to stuff like Cruise Control, Rock Crawl modes, and so on. Which ID is used by the logic depends on what you're doing (Cruise Control), shift situation, accel factor, etc. It all depends on what that type is used for.

    Attachment 81475

    For example, if you have cruise control active with accel factor 1, this particular setup will use Shift Pattern/ID 35 no matter what shift situation you're in.


    BUT WAIT, THERE'S MORE.
    Even once you know this final shift pattern ID, it can be remapped into another ID entirely by one final table. On the ZF8 we tried to show this with a bunch of comboboxes, but ZF9 and moving forward we'll just show the raw table.
    Attachment 81476

    For our example, Cruise Control, Accel Factor 1, we desired pattern 35. However, this final step maps Pattern 35 to Pattern 67. Pattern 35 is never even used!



    I wish I could tell you this is easy or straightforward, but its not. It's a lot to swallow and understand. Transmissions are getting easily as complex as engine controllers, and the ZF especially so because its designed to be used in so many different applications by different OEMs. Because of this insane amount of configurability for the OEMs, the actual mapping itself is equally as configurable.

    Hopefully if you read through this a few times and try to follow along with your calibration, you can start to understand it a little. If you have more questions, just ask, I'll try to answer them as I can!"
    ------------------------------------------------------------------------------------------------------------------------------------


    I did some logging today today to check what shift strategies are in place here in my application
    the SXT doesn't have sport or performance mode, we only have an ECO mode switch, and i have to press it to disable ECO mode every single time. Should be easy right compared to the R/T or SRT8

    So i'm running V4.8.7, and i don't see a PID for Clutch Shift type. Do i need the beta to tune the 8 speed in my 2014 Durango ?Also I don't have performance anything options. is either Eco on which is the default when you start the SUV or you disabled the Eco crap just pressing the Eco option to disabled it.

    Logging with scanner i can see the Trans Shift mode PID changing from 0 (With Eco on set to Off)
    eco_off by RAM RSM, on Flickr

    to Trans shift mode 512 (With Eco On),
    eco_on by RAM RSM, on Flickr

    and if i look into the some of the trans values i can scan with Scanner v4.8.7 i can see for example commanded gear = 2, even at 2mph coasting so my feet is off the trottle, Trans shift situation 2 when Eco on, Trans shift siuation 0 when Eco is off

    1.) 1st question looking to just change the shift point for the 2-1 downshift so we don't need to come to a full stop to engage 1st gear, the tables i need to change will be in shift scheduling correct ? this is the area where the shift points are adjusted ?

    2.) how do i correlate the the shift aggression pattern using that Trans shift mode 0 or 512 for Eco on or eco off in the logs to what Steven is explaining.

    I see for example in the Trans normal 0 Aggression the output shaft speed RPM is only 7rpm for the 2-1 downshift at 0 acceleration throttle position, see print screen. I'd assume this is one of the tables i need to change to say 100rpm output shaft speed to have a 2-1 downshift at say 2-3mph ?
    trans shift normal 0 by RAM RSM, on Flickr

    Thanks a lot.
    Attached Images Attached Images
    Attached Files Attached Files
    Last edited by bluegoat06; 10-02-2020 at 08:35 PM.

  2. #2
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    You need to be able to log shift ID. Without that, you won't know for sure which of the 90 tables you're accessing during that downshift that you want to change. Send a ticket into support to have them add that for you in Beta, but first try the latest Beta to see if it's in there.

    There is a good chance it's one of the 5 (0,1,2,3,4) Normal aggression tables (probably 0), which you can simply make the same change to all of them.

    Log output shaft speed and throttle position and decide when you want the shift to happen and plug it in. It's probably going to be more than 7rpm! LOL Try replacing those 7s with something like 250 and see how that grabs you.
    If in doubt, multiply everything by 1.1.