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Anyone notice the other regen braking dropout?

Discussion in 'Gen 3 Prius Technical Discussion' started by Lewie, Feb 5, 2010.

  1. Lewie

    Lewie Junior Member

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    Now that the bump-induced regen braking dropout issue has been identified, has anyone noticed another less obvious dropout when slowing gently through 7-MPH? I noticed it this morning and it has the same, but much smaller feeling, as the bump induced one. I was slowing gradually to a stop at a traffic light when I felt the deceleration drop for 1/2 second or so before the friction brakes kicked in. When they did, the deceleration was not as great as the regen's, requiring that I increase the force slightly on the brake pedal.

    I wonder if the software fix for the bump-float will fix the normal regen dropout float at 7-MPH? This could also be a low-speed safety issue.
     
    #1 Lewie, Feb 5, 2010
  2. georgew

    georgew New Member

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    I only feel that when my rate of de-acceleration is REALLY slow...the effect is so small I find it hard to see how it can be a safety issue....at least If i'm in the driver seat. :)
     
    #2 georgew, Feb 6, 2010
  3. seegarman

    seegarman Junior Member

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    Yup, I've experienced the same dropout too. At first this quirk distrubed me since I'm accustomed to a linear feel to braking while driving cars with mechanical brake systems and I like coming to a full stop smoothly.

    Now after 6000 miles, I am anticipating the dropout and just apply additional pressure to the brake pedal. No I do not like this condition and I hope the "fix" will solve this quirk too but I can live with it.
     
    #3 seegarman, Feb 6, 2010
  4. wvgasguy

    wvgasguy New Member

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    #4 wvgasguy, Feb 6, 2010
  5. wvgasguy

    wvgasguy New Member

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    #5 wvgasguy, Feb 6, 2010
  6. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I don't have a 2010, but on all Gen2 Prii, 7mph is the magic speed at which regen starts/stops. If you ever find yourself creeping to a four-way stop (for example) you will notice that if you roll at 8mph, you will have regen. At 7mph, you will have coasting. At 6mph, the battery will propel the car. (Keep in mind that my experience is limited to the Gen2)

    So to answer your question, whether people recognize it or even feel it or not, every Prius driver has experienced it at one time or another.
     
    #6 TonyPSchaefer, Feb 6, 2010
  7. garygid

    garygid Senior Member - Blizzard Pearl

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    My 2010 Prius-III (mfg July 2009) seems to have very smooth regen, even at low speeds, with an undetectable transition (if any) to mechanical brakes.
    I will watch the low-speed regen next time I drive.
     
    #7 garygid, Feb 6, 2010
  8. Tom183

    Tom183 New Member

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    I wouldn't call it a "drop-out" as the car continues to slow down. I think Car&Driver described it best by saying the Prius brakes are "non-linear".
     
    #8 Tom183, Feb 6, 2010
  9. cstone47

    cstone47 New Member

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    +1 on the experience and in hoping the "fix" cures it. BTW, I'm at 2000 miles.
     
    #9 cstone47, Feb 6, 2010
  10. pakitt

    pakitt Senior Member

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    I haven't noticed it (at 8000km). I don't know exactly when my car was built because the EU tag is completely different from the US one - I don't know how to find the manufacturing date...
     
    #10 pakitt, Feb 6, 2010
  11. adrianblack

    adrianblack Member

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    I've never felt this on my Gen III either. (Nor the other braking issue.) From 30 to zero with constant pressure gives very nice linear stopping and the transition from regen to full friction is seamless (on my car, at least.)

    I remember the car mags saying the brakes were "interesting" on the Prius -- perhaps earlier Gen III's were like this?

    It's almost like the amount of braking force the friction brakes are giving is less than what the ECU expects -- this could account for both people are having. Once regen cuts out, the friction brakes aren't doing enough and you have to push harder on the pedal.

    There is a calibration you can do with TechStream called "Linear Valve Offset Learning" ... it's supposed to take a couple of minutes to run and the car does it's thing on its own. The manual doesn't say what happens when this calibration is wrong ... and if you change parts of the brake system you need to re-run it.

    There is another calibration for the G-force and yaw sensors. I don't think this is related...
     
    #11 adrianblack, Feb 6, 2010
  12. brad_rules_man

    brad_rules_man Hybrid electric revolutionizer

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    Mine definitely drops out at lower speeds, but I heard that it decreases the lower the speed gets and the friction brakes take over. I mean, I obviously knew that much, but 7-4 it cuts out and 3-0 I think it's so inefficient that it's not worth it.

    Something to that effect.
     
    #12 brad_rules_man, Feb 6, 2010
  13. ScottG10

    ScottG10 Member

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    I can always feel the transition but my wife cant. I guess it just depends on the person.
     
    #13 ScottG10, Feb 7, 2010
  14. LeeB

    LeeB Junior Member

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    My experience exactly. I can hear the regen on my September 2009 build, but the transition to friction is seemless to me. I'll also pay more attention next time, if the snow melts enough to get the Prius out of the garage.
     
    #14 LeeB, Feb 7, 2010
  15. garygid

    garygid Senior Member - Blizzard Pearl

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    It "seems like" the regen braking continues below 8 mph.
    I have not been able to detect any "transition" from regen to mechanical.
    To me, it seems to be perfectly integrated with a totally hidden transition.

    My thought has been (and I tend to be critical), "Well done, Toyota!"
     
    #15 garygid, Feb 10, 2010
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