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Thread: 6L80E with big horsepower

  1. #21
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    For now, just assume the shift is based off MPH and set the RPM shift at what you think it should be at that MPH. Allow for 600RPM above that and set the fuel cutoff there.

    You will need to account for tyre growth, tyre size and overall gear ratio.

    Do it this way...

    1. scale the final gear ratio and tyre size correctly
    2. set the desired WOT RPM shift
    3. set the desired WOT MPH shift
    4. if it bounces, set the speed shift 5PMH lower
    5. keep doing (4.) until it is where you want it

    HPT just makes available the table data - they don't define the control logic for the A6 (that's GM's job)

    *** just because something is visible doesn't mean it is actually used ***

  2. #22
    i know this isn't the way to the fastest car but what if you lowered the power at lets say 6000rpm to help it get thru the shift. maybe use the "max tq" in each gear tables. reset the rpm axis so you can put in numbers at the higher rpms, then set the tq down some. i am guessing it would pull some timing and get he power down. another option would be a speed based boost controller or some other type of boost control that would pull the boost down at a certain rpm/speed to help it shift.

  3. #23
    Senior Tuner Mep_q8's Avatar
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    oh yeah, this is coming from the king of trucks! lol, it's a pleasure

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  4. #24
    Any solution to this yet? My buddy's 08 C6 has the problem of not wanting to shift into 4th gear at the topend when using nitrous. He ends up trapping at around 7000rpms in 3rd.

  5. #25
    i am getting my ass kicked at 500rwhp. that 3-4 shift is tuff.

    dont suppose anyone with high hp and a well working trans program would care to share?

  6. #26
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    Quote Originally Posted by parish8 View Post
    i am getting my ass kicked at 500rwhp. that 3-4 shift is tuff.

    dont suppose anyone with high hp and a well working trans program would care to share?
    are u still using some TM on the tranny side?

    u still letting it drop some power at shifts? seems to make it better if u ask me.
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  7. #27
    Advanced Tuner midevil1's Avatar
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    For vehicle's making 470rwhp and less I use no TQM for racing tunes. Above this number I have had great success with 10% TQM added to first 4 forward shifts. GM puts a limit of 469hp on this gearbox and they mean it. The 300mm converter boxes seem to handle more power than the 258mm boxes. A window switch for power adders is highly recommended for converter life. With PWM lockup any major slip detected by the TCM will result in a "NO" shift scenario....
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  8. #28
    what do you mean by a window switch? It sounds like you are assuming lockup during shift, whereas most people would leave the TCC unlocked at wot.... in which case there is always slip.

  9. #29
    Advanced Tuner midevil1's Avatar
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    Quote Originally Posted by icicleboy View Post
    what do you mean by a window switch? It sounds like you are assuming lockup during shift, whereas most people would leave the TCC unlocked at wot.... in which case there is always slip.
    Not for lockup but for the shift. Locking the converter at WOT is great for dragracing, but you better have BILLET shafts and billet muti-disc converter.
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  10. #30
    Quote Originally Posted by midevil1 View Post
    With PWM lockup any major slip detected by the TCM will result in a "NO" shift scenario....

    what about cars that are trying to make a shift WITHOUT locking the converter? that means slip is inevitable even on OEM applications with low power.

  11. #31
    Advanced Tuner midevil1's Avatar
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    "Major" is the keyword. Just because a converter isn't locked doesn't mean it is "slipping". Factory converter slippage in a stock app. is virtually non- existent. I am working on a ZF tranny that uses a "clutch, pressure plate" and TQ Converter setup. Converter to get the power moving and clutch to shift the tranny. No 3rd pedal BTW.....
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  12. #32
    Tuner TYRFRYR's Avatar
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    Quote Originally Posted by INTENSE-Racing View Post
    It almost seems like parts of the upshift table are random, or there’s some other contributing factor here that I am unaware of.
    Since the ECM and TCM are separate controllers, the TCM may be relying on the CAN bus to acquire engine speed and wheel speed. If so, the irratic behavior could be the result of network latency.

    This could also help explain why there is a relatively unpredictable delay between a Manual Mode shift command and the actual transmission shift.

  13. #33
    TYRFRYR, I could see that being a contributing factor.

    I have had this problem with 1000+hp 4l65's, just have to lower the shift point, pull timing close to the shift and use TQM. They can then be a little off from time to time depending on trans temp and track prep.

    I have had good luck on the G8's to 600hp, but I have not tuned any making more then that yet.

  14. #34
    Tuner TYRFRYR's Avatar
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    Another thing that I noticed today while I was working on the 2-3 shift was that even when I had the pedal pressed to the floor, the WOT status bit was not on.

    By intuition, that tells me that the part throttle shift schedule is going to be used.

    When I looked at the data logs, and compared the actual shift point to the settings in the part throttle table, they matched.

    What we probably need to do here is collect some data that correlates engine speed and wheel speed. Unfortunately every car will be different based on the converter and power level.

    Based on the collected data, update the part throttle shift table from say 70% and up for each gear to a speed that has you shifting at the RPM you want.

    Update the WOT shift speed to match what you put in the Part Throttle table and set your WOT RPM to match.

    Any thoughts???

  15. #35
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    i was having the same shifting issue, and then i got an updated tune and it will now shift fine, but am having another issue just on the 2-3 shift.

  16. #36
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    flare 4 gear 6l80

    Quote Originally Posted by soundengineer View Post
    try setting the WOT shift MPH upshift to 0
    and set all of the shift properties desired shift times to 0

    this will help a lot
    problem is that the tranny is just really slow so you have to set it somewhat early...
    by getting rid of the adaptive shift learning(the desired shift times set to 0) you gain some control over it and can make it predictable