2010 brake system

Discussion in 'Gen 3 Prius Technical Discussion' started by bwilson4web, Jan 30, 2010.

?

Details on braking anomoly

Poll closed Feb 13, 2010.
  1. Happens in the beginning of braking

    19.4%
  2. Happens after braking for a bit

    79.1%
  3. Had a load in back of Prius

    1.5%
  4. No significant load in Prius

    70.1%
Multiple votes are allowed.
  1. tpfun

    tpfun New Member

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    I don't understand the lack of additional X deceleration on hitting the speed bump. When the wheels hit the bump, there should be an additional force component in the -X axis. Instead, the graph seems (eyeballing in lieu of a best curve fit) to indicate the opposite.
     
  2. KK6PD

    KK6PD _ . _ . / _ _ . _

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    Bob, NICE JOB, I am impressed with diligence, you shuuld hold a presser since Toyota has not and explain whats going on!!!!
     
  3. bwilson4web

    bwilson4web i3 and Prime

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    Monday morning we had a mix of snow, sleet, and wet streets. Instead of taking the wife's ZVW30 (2010 Prius), I took the NHW11 and started the accelerometer. I tried to drive over every speed bump, hump, pothole, railroad track including the speed bumps into Redstone Arsenal that showed the braking anomaly ... nothing.

    A negative result is not conclusive because we know it is an intermittent problem. It just means I haven't in a winter sleet/snow/rain mix been able to replicate the problem with our NHW11. However, the deceleration rate was consistent with the ZVW30.

    Bob Wilson
     
  4. mmurphy

    mmurphy Junior Member

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    According to an AP story this morning:

    "The Toyota executive overseeing quality Shinichi Sasaki said the delay that Prius drivers can feel when braking lasts for a fraction of a second as the antilock brakes kick in.

    The problem happens only on snowy or bumpy surfaces, and the complaints did not become more numerous until recently when the weather got colder, Sasaki said. "

    I've followed the PC discussion for a few months and haven't seen much on problems due to cold / slippery conditions or the antilock system.

    Can anyone help resolve the apparent discrepancy?
     
  5. qbee42

    qbee42 My other car is a boat

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    Ice and snow can certainly cause the regen/ABS transition that is at the core of the braking issue. Perhaps the reason that you don't hear about it much on PC is that most of us accustomed to driving in winter conditions are also accustomed to loss of traction and braking. Winter driving isn't for sissies. Regardless of what type of car or truck you drive, if you drive in winter conditions you expect braking and control problems.

    Tom
     
    3 people like this.
  6. bwilson4web

    bwilson4web i3 and Prime

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    In parts of the South, any rain makes our streets and roads exceptionally slippery. We noticed it 25 years ago when we moved to Huntsville Alabama and don't even think about any more. So we may have have had it happen before but not noticed it until folks starting describing it.

    Even though it may be galling to some, those who brought the problem to our attention deserve a "thank you." And from my point of view, those who put up with my pesky polls and questions, "Thank You Very Much!" And those who mindlessly "cut and pasted" opinions without bringing any facts and data ... still <ploink>.

    Bob Wilson
     
  7. energyandair

    energyandair Active Member

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    Great work Bob.
    I have been thinking about why the time (almost 1 sec) and distance your charts show lost braking might be so much longer than I recall in my 2 incidents and why peoples' reports and impressions vary so much.
    My impression is that most individuals sense fairly consistent behavior.
    One possibility is that individual cars are different.
    Another might be that different people might sense and control braking differently.
    I believe that your charts were based on constant brake pedal position.
    It would be very interesting to see what it looks like with constant pedal pressure.
    My guess is that both time and distance would be substantially less.
     
  8. mmurphy

    mmurphy Junior Member

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    Good idea! I'll bet if slippery conditions caused the regen/ABS transition, I'd never notice a brief delay in friction braking. I'd just assume lack of traction was at fault.

    I have experienced the bump-induced brake delay (very rarely), without any indication of ABS involvement. That’s why I wondered why Toyota was emphasizing delay in the antilock system.
     
  9. bwilson4web

    bwilson4web i3 and Prime

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    Remember, that was one instrumented incident. In any population of measured incidents I would expect to find a Gaussian distribution of values. In fact, many may occur below the level of human perception, ~200 ms.

    What I would recommend is if you've been thinking about getting an iPhone or an iPod Touch, you can get software that makes them into an accelerometer. Before the patches show up, it would be nice if we could gather a population of documented incidents. Then after the patch, we can see what the new data under similar conditions looks like.

    IMHO, this is not the end of the problem or even the beginning of the end of the problem but rather the end of the beginning of the problem (Winston Churchill.)

    Bob Wilson
     
  10. fuzzy1

    fuzzy1 Senior Member

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    Winter driving responses are the other half of what saved me from a long-ago Sudden Unintended Acceleration, really a fatigue-induced pedal misapplication. Despite the fatigue, and being in the middle of summer, the right foot reflex responded as if the 'failed' brakes were locked on slick roads, and moved to unlock them. (no ABS in that car.) Incident terminated.
     
  11. garygid

    garygid Senior Member - Blizzard Pearl

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    A very brief skid (for me, 1 foot on a wet pedestrian crosswalk line) or
    a "sufficient" bump apparently triggers the skid-sensor, which results
    in the regen braking being turned off for about a second.

    Even if one is FAST, it takes about a half second to realize what is happening,
    and another half second to figure out what to do about it.
    By then, you might have gotten too close to avoid a crash.

    And, for most of us, the first time it happens, we are just NOT that fast.
    Persons not knowing about it at all ... will likely be slower yet.

    So, the "fix" that Toyota has been putting in new-manufacture cars for about
    a month, is now available to the rest of us.

    Thanks, Toyota!
    I got it "installed" today.
     
  12. adrianblack

    adrianblack Member

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    While the SGII is slow to update and might not be hugely useful here, I added 3 new XGAUGEs to my spreadsheet tonight:

    - Regen Cooperation: On or Off depending if Regen braking is actually happening or not
    - Regen Requested: Shows in NM what the Skid ECU is asking for Regen wise
    - Regen Operation: Shows in NM what the Hybrid ECU is actually delivering in regen braking


    https://spreadsheets.google.com/ccc?key=0AiHL0r_2nhUEdF9lVVBxOVNoN3Zva3E0NmdZTUR1eVE&hl=en

    Could be useful to see if regen really kicks off at the slightest hint of ABS activation, etc etc.
     
  13. bwilson4web

    bwilson4web i3 and Prime

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    Thanks "adrianblack" for the scangauge hack. I don't have one but it looks to be helpful. But I wanted to sum things up:

    • 19 mph - threshold speed for regenerative braking referenced on page BC-49 in the 2010 Maintenance Manual
    • 7.9 m/sec (17.67 mph) - entrance speed to speed bump showing problem but requires a wet street for braking pause
    • 7.6 m/sec (17.00 mph) - exit from speed bump with brake paused, requires "wet street" condition on Huntsville roads, notoriously slippery
    • 700-800 ms. - duration of braking pause 5.32-6.08 meters (17.4-19.9 feet)
    • 22 images of street and road conditions
    • SSC-A0B - title of the skid control ECU fix (thanks "john1701a")
    Bob Wilson
     
  14. dzaky

    dzaky New Member

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  15. dzaky

    dzaky New Member

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  16. eric1234

    eric1234 Active Member

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    Hi - Are these documents :"New Car Features" publicly available? I've done a Google search, and the only result is this very thread. :)

    I think they'd be interesting to review.

    Thanks,
    Eric
     
  17. mjones12

    mjones12 Member

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    What a pompous a-hole you are. Strike one, right?
     
  18. mjones12

    mjones12 Member

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    PLOINK you and the Prius you rode in on. Strike two, right? Go ahead, get even.
     
  19. a priori

    a priori Canonus Curiosus

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    I'm trying to figure out what's going on here.

    You have the first two posts in a thread that had not seen any activity for two and one-half years. My hope is that you were looking to read up on braking anomalies in the 2010 Prius. If so, I'd also hope you would be engaging in some sort of positive discussion, like you have in the past.

    If you have some other objective or a particular beef with Bob Wilson, then say it straight out.
     
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