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Thread: Engine braking ZF8HP70

  1. #1
    Tuner EVguy1's Avatar
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    Engine braking ZF8HP70

    I'm slowly figuring out my mapping but have not figured out how to add more engine braking when going down a hill. When using cruise control it must do some engine braking to try to maintain speed going down hills? How do I replicate that in Sport mode?

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    Tuner EVguy1's Avatar
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    Once again I appear to have asked a question that no one knows, I'm good at that.
    Let me ask this, what dictates downshifts at zero throttle?
    If the 2>1 shift is set at 80 in the pattern tables, I would think that means the trans will make the 2>1 shift when OSS is at 80 RPM but at that point engine RPM would be less than idle RPM so I imagine that TC has unlocked and we are basically coasting?
    Will raising the 2>1 shift point to something like 450 OSS then allow a downshift to happed where the engine RPM is still high enough to do some braking as long as the converter is still locked?
    OR do I have the whole downshift theory wrong?
    What's the difference between downshift under acceleration (kick down) and downshift under zero throttle while slowing down?

  3. #3
    Tuner EVguy1's Avatar
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    Thanks for the response spoolboy. I have been playing with the shift map tables for a long time and have off throttle downshifts happening quite well but had to bump up the down shift OSS by quite a bit. I was just concerned that I was missing something else. So what is the spontaneous downshift map??
    If I'm cruising long in say 4th gear and punch it, it does not gear down, it pulls like a freight train but no downshift.

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    The way I do it is:
    Do the calculation for each gear (based on transmission gear spread) and than apply it to the tables you are during the situation.

    I do not like/recommend only multiplying everything to any value. This could either make it to aggressive or even prevent the shifit -> not even touching the shift harmonization.

    The way I do: https://www.youtube.com/watch?v=pvmaW3YmmGw

    Dodge Boy

  5. #5
    Tuner EVguy1's Avatar
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    This was the best reply I have had on this forum. I now have a very effective tune. I was a bit of work to get it just right as I'm a fussy old fart but DB was able to set it up just the way I wanted. Highly recommend!

  6. #6
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    I've noticed on my ram with vcm scanner that coasting downhill will almost always kick it from map 5 to map 0, and then spontaneous downshift occurs if you touch the brake

    You could do the same with your car and see which map is uses when coasting. Ram is almost always 5, 0 when coasting downhill and sometimes 10 or 15 when riding up a hill

    Cars are mapped a little differently so vcm scanner will be your best friend

  7. #7
    Tuner EVguy1's Avatar
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    Quote Originally Posted by donald7150 View Post

    Cars are mapped a little differently so vcm scanner will be your best friend
    I spent hours logging, tuning, logging, tunning etc and never got it just the way I wanted it. In just a few tries Dodgeboy_8HP made it perfect. Sometimes it pays to pay. ;>)

  8. #8
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    Hello donald7150,

    In case are looking for a specialized and personalized trans tune support, I am more than willing to support you!

    Please, get in touch via email: [email protected]

    Dodge Boy (https://www.youtube.com/@dodgeboy2785)