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Thread: 6l80E 3-4 shift, Track only, can somebody at HPTuners take a look to see if there is

  1. #81
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    Quote Originally Posted by Bluecat View Post
    What you guys log would make a big difference on what I can see. The data rate is so fast on the new stuff there is no reason to not have your pid table full. Doing trans tuning I "need" to see Trans current gear, Delivered engine torque, PCS Pressure 1 - 5, TCC Line pressure, and tcc slip rpm. Would "like" to see if you have room, trans temp, Time of last shift, Trans calculated gear ratio. On the gear ratio part, that pid maxes out at 4.0. That is actually less that what first gear is. I chased my tail for years on cars that had 1>2 trouble because of this. The tranny can be slipping in 1st, but youll never know it because the pid it truncated. If you log trans input and output, and make a custom pid for trans gear ratio, you can really tell more about whats going on in 1st gear.

    Get me a log with all that data, one that shows a bad 1st 3>4 wot shift and then a subsequent good 3>4 wot shift and maybe we can get to the bottom of this. Plus a copy of the tune that was used to make the log.
    Be awesome if someone can get this happening. My car is away for the winter but if no one can do it before, I will when she comes out to play.

    Thanks Bluecat for offering to try and figure this out.
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  2. #82
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    Quote Originally Posted by SK360 View Post
    Blue,

    Don't exactly remember the feeling since I have been doing all I can to avoid that shift at the track since.

    But I can tell you that even driving it around at 10% throttle, letting it complete a 3-4 shift at 20 or whatever mph then going WOT, there are no issues with the shift. Same with getting it into 4th in the waterbox.

    It happens on bone stock cars on stock tune as well.

    I can do more logging once winter ends.
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  3. #83
    Advanced Tuner Dr. Nopps's Avatar
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    I could be the farthest from the diagnosis here, (never stopped me before) but it seems like this may be a mandatory pre-overdrive diagnostic cycle as it has to be repeated after a cool down, and for EVERY drive. I would wager a guess in this case that after a certain fluid temperature is reached, a calculation/comparison may be determined when engaging 4th to assure that there actually is in fact the expected 1 to 1 drive ratio, or some figure within tolerance. Now hopefully where that data is stored, (TCM, PCM?) and how to freeze it in there or bypass the diagnostic will be the next task driving you guys crazy.

  4. #84
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    Quote Originally Posted by Bluecat View Post
    I'm still not seeing it. I understand what your talking about. Obviously it exists, 04blackgmc stated that it will even cause it to hit the limiter sometimes. What you guys are describing I should be able to see in a log, I just haven't seen it yet, lol. First off, based off what 8850 said, your calculating your shift times completely wrong.

    Let talk about how the 6L's shift in general. Being a clutch to clutch transmission, it does a pre-shift kind of prep. The hand off from one clutch to the next is a tricky process to implement smoothly without a bog or a flare. To ensure the max amount of consistency, it pre loads the oncoming clutch with a light amount of pressure to ensure its ready to strike and to make sure their is no air in the circuit. Under normal part throttle shifting it does this for a small amount of time (usually less than a second) and then kicks off the shift. The pre-shift prep is where our delay comes from in manual mode. It can't instantly shift when you slap a paddle because it wants to get everything ready first, which takes time.

    In wot mode where the rpm qualifier is also used, it happens a little different. When the mph for the shift speed is met it goes ahead and changes to pre-shift mode. You will see the current gear change in the scanner, but that dosen't mean a whole lot. That doesn't mean its trying to shift, its just getting ready. Under normal circumstances the noid for each gear is basically solid on, and the line pressure noid is modulated to control the pressure to the clutch. When it goes into pre-shift mode they flop. The line pressure raises to the "shift pressure" and it starts modulating the noids for the on and off coming clutches. You will see it preload the oncoming gear just a little to get it primed. Then it waits... until the rpm qualifier is meet and actually kicks off the shift. So to say that the shift took "x" amount of time based off when "trans current gear" changes is incorrect. If there is a long amount of time between those events, all that means is that your wot shift speed is to low compared to what your have your wot shift rpm set to. It won't actually shift until both rpm and mph are met, but it starts getting ready as soon as mph is met (which is when you see "trans current gear" change)

    From the 10.949 log above posted by 8850:

    2-3 Shift starts at frame 3986 - 1:39.606s / Ends frame 4003 - 1:40.043s = 0.437s
    3-4 Shift starts as frame 4186 - 1:44.614s / Ends frame 4199 - 1:44.941s = 0.327s

    The 3-4 shift is a faster shift. Its even a better looking / cleaner shift by just looking at the rpm line compared to the 2-3. Which is what I look at when I look at a shift in a log. Both shifts kick off at about 6500, which I'll assume is what the wot shift rpm is set to in the tune. I seen no problems with the 3-4 shift in the mentioned log above.



    But, that doesn't do anything for addressing the problem. Obviously there is something going on or there would not be so many of you reporting it. Now, the log above doesn't show it, but I did notice something in a few of the other logs I looked at in this thread. The incline of the mph line shows the acceleration of the vehicle. I noticed in at least one log that the car was flat at the top of 3rd and not doing a whole lot. At first I assumed it was just someone shifting a car at 6500 that needed to be shifted earlier, lol. But then I though maybe it was pre-shift mode dragging the car down. The down side of setting the shift speed to early is that it does stay in pre shift mode a long time. And if the pressure used to prime the oncoming clutch is to high, your actually dragging the car down and burning up your clutches while you waist HP. The tcm is always learning and adapting. It may be that what is happening is to heavy and long off a pre shift prime pressure that is getting corrected for in subsequent shifts and is getting lost on a key cycle. On the first shift where you are seeing the problem, does it feel like the brakes are dragging and the car is smothered at the top of 3rd?

    Everything you are saying here makes sense, but it just doesn't seem to line up in my logs. I went back to a track day and compared the logs to the tune.

    Each gear starts the shift at exactly the mph I have set in the tune... which corresponds to what you are saying. The problem comes because the when the shifts actually occur, doesn't match at all the rpm I set them for.

    For example the 3/4 shift. Set at 30mph and 6300 rpm. The shift start at 30mph exactly but completes at 38mph / 6750rpm.
    I then changed the RPM down to 5800 to try and get it to shift earlier. It triggered and shifted at the same spots again. It seems the rpm is not having any effect, which is what Chris (subfloor) has always said.
    Getting it to trigger is easy, by mph, but getting it to actually shift where I want has been another story.
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  5. #85
    Advanced Tuner Bluecat's Avatar
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    Let me catch up with you here. In the example you said 3/4 shift, but list speeds in the 30's. I'll assume you are actually talking about the 1/2 shift in your example.

    Especially in 1st gear where things are happening fast, things have to be lead. Like I mentioned above, the preshift process takes time. If it starts at 30, and is not ready to strike until 38, then setting the rpm lower than what 38mph corresponds to isn't going to make it shift any earlier. Set the mph lower to like 20, then experiment with rpm changes. Especially in 1st gear with a high powered car both rpm and mph will have to be lead alot. I often set the mph to what 4000rpm would be so that it has plenty of time to get ready in preshift mode (only talking about 1st gear here). If you want it to shift @ 6300, you might have to actually set the rpm to 5600 or so to make it happen. If you watch what my trans program does, you'll see it leads all the mphs, more so in the lower gears. But it only leads the rpm in the lower gears when the lead setting starts to get cranked up. (rpm leads only show up when your ready to paste out from the export screen)

    Now to throw a monkey wrench in here. Saying that rpm doesn't make a difference can actually be taking place. There are tables we don't have in HPT that show if the wot rpm qualifier will be used. Lot of stock cals don't use rpm for 1/2 - Almost all do for the 3/4. It's been this was since genIII stuff. Back then speed was the only thing used for 1/2 and then rpm was included in the later gears. The newer calibrations seem to follow the same pattern. When the rpm qualifier is not used, it follows the same process it does when not at WOT. As soon as the pre shift process is ready and complete, it just goes ahead and shifts. Clear as mud now?

    Here is a screen shot from brand "C".

    Rpm_Qualifier.JPG
    Last edited by Bluecat; 02-23-2014 at 05:14 PM.

  6. #86
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    Quote Originally Posted by Bluecat View Post
    Let me catch up with you here. In the example you said 3/4 shift, but list speeds in the 30's. I'll assume you are actually talking about the 1/2 shift in your example.

    Especially in 1st gear where things are happening fast, things have to be lead. Like I mentioned above, the preshift process takes time. If it starts at 30, and is not ready to strike until 38, then setting the rpm lower than what 38mph corresponds to isn't going to make it shift any earlier. Set the mph lower to like 20, then experiment with rpm changes. Especially in 1st gear with a high powered car both rpm and mph will have to be lead alot. I often set the mph to what 4000rpm would be so that it has plenty of time to get ready in preshift mode (only talking about 1st gear here). If you want it to shift @ 6300, you might have to actually set the rpm to 5600 or so to make it happen. If you watch what my trans program does, you'll see it leads all the mphs, more so in the lower gears. But it only leads the rpm in the lower gears when the lead setting starts to get cranked up. (rpm leads only show up when your ready to paste out from the export screen)

    Now to throw a monkey wrench in here. Saying that rpm doesn't make a difference can actually be taking place. There are tables we don't have in HPT that show if the wot rpm qualifier will be used. Lot of stock cals don't use rpm for 1/2 - Almost all do for the 3/4. It's been this was since genIII stuff. Back then speed was the only thing used for 1/2 and then rpm was included in the later gears. The newer calibrations seem to follow the same pattern. When the rpm qualifier is not used, it follows the same process it does when not at WOT. As soon as the pre shift process is ready and complete, it just goes ahead and shifts. Clear as mud now?

    Here is a screen shot from brand "C".

    Rpm_Qualifier.JPG

    You are right. I was rushing earlier and meant to use the 3/4 shift but put numbers from the 1/2 .

    The 3/4 is set to change at 88 , and does start the shift there.. The actual shift occurs at 97-98 mph. Again, changing rpms didn't have much effect. When set to 5800, it shifted at about 6600.

    I have to play with it more when the snow melts, but I always have the same problem. It starts the shift where I want it to, but the completion is just not very consistent.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
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    ARH 1 7/8 headers,
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  7. #87
    Tuner hivoltagedriver's Avatar
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    Just to add to this, I have experienced the same problem. I thought it was fixed with my most recent tune because it behaves well on the street, but my last trip to the track proved me wrong. I got the opportunity to hot lap after sitting for a while, and picked up the better part of 2mph and got my best pass ever. As a matter of fact, I made three passes in a row and got quicker each time.
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  8. #88
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    Bump - anyone figure out a way around this besides running through the gears in the burnout box or staging lanes ?

  9. #89
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    Quote Originally Posted by Maxspeed96ct View Post
    Bump - anyone figure out a way around this besides running through the gears in the burnout box or staging lanes ?
    not yet that i am aware of.
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  10. #90
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    Once the weather clears up ill try to get it to happen again for me while logging.

    What if I just disabled abuse mode? what negative impact would that have and would it help?