Traction Control feature

Discussion in 'Prime Technical Discussion' started by EdTechGuy, Feb 22, 2021.

  1. EdTechGuy

    EdTechGuy New Member

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    This is my first winter with my 2020 Prius Prime, and I finally found a reason to use the Traction Control button. I found that while climbing the icy hill in the alley leading to my garage, my Prime brakes were pulsing crazily and the car wouldn't climb the hill. I found that hitting the "TRAC" button let me spin my way up, as all my past cars have been able to do. Great! And there's no way to forget it's off, since the on-screen message overrides my other info display.

    The manual makes it sound like Traction Control interacts with other systems and generally shouldn't be used. Has anyone found other scenarios where turning off Traction Control is helpful?
     
  2. jdenenberg

    jdenenberg EE Professor

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    One of my very few complaints about my Prii (I'm on my third one) was the so-called "traction Control". In the early days (my 2004), it was actually there to protect the drive train from sudden, high torque, events (a spinning wheel hitting a patch of dry pavement) and breaking something. There were much better solutions to that problem than shutting down the drive train when a wheel slip occurred. There is already a torque limiting clutch between the engine and the HSD that deals with excess torque at that point in the drive train. Two more of those clutches, one in each half shaft, would protect the system and not leave me vulnerable to being broad sided when the Prius stops while accelerating into traffic and a bit of slippage occurs due to sand on the road.

    My new 2020 AWDe Prius does not exhibit this issue due to the extra traction from the rear wheels so all is good now.

    JeffD
     
  3. ChapmanF

    ChapmanF Senior Member

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    The first-gen Prius (2001-2003) did indeed have a "traction control" that could not do anything but limit power, and was really only there to prevent the magnets in MG1's rotor taking an unscheduled departure from the car.

    With Gen 2 (2004 on), there was a traction control like those in other cars, where it can detect if a particular wheel is slipping and selectively apply the friction brake on that wheel, keeping more power available to the wheel that isn't slipping.
     
  4. jdenenberg

    jdenenberg EE Professor

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    My experience with my 2004 was that the brakes were not involved (my 04 just stopped). This may have been introduced with the 2006 update to the design, but I never looked into it.

    JeffD
     
  5. ChapmanF

    ChapmanF Senior Member

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    See page TH-47 of the 2004 New Car Features manual.

    [​IMG]
     
  6. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Snow tires? They’ll help a lot too.
     
  7. jdenenberg

    jdenenberg EE Professor

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    Note that it says "if one of the wheels", when both spun my 04 Prius just shut down the engine(s) so getting up my driveway was sometimes a challenge. The problem was greatly improved when I replaced the OE tires after a few years first with Michelin MXV4+ and then later with Nokian WRs.

    JeffD
     
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  8. m8547

    m8547 Senior Member

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    In my experience the traction control on the Prime could use some fine tuning. If one of the wheels loses traction it should pulse the brakes to that wheel so that the wheel with grip also has torque. Sometimes it works, but sometimes it allows excessive wheel spin which is counterproductive and risks damaging the drivetrain if the spinning wheel suddenly gets traction. It seems to work OK once the car is moving, but from a stop or especially if the steering wheel is turned it often allows excessive wheel spin. I mostly drive in EV mode, so I don't have much experience with how it behaves in HV mode. Turning traction control off should allow as much wheel spin as you want, but I can't see how that would help in most situations.

    I also have a Toyota 4Runner, and it's ability to use the brakes to transfer power is incredible. It works almost as well as a locking differential. I can crawl up obstacles off road with one or two wheels in the air. So Toyota is capable of programming a system that makes good use of available traction.
     
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  9. ChapmanF

    ChapmanF Senior Member

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    Naturally, if there are only two driving wheels and more than one is spinning, that'll be a challenge for even the cleverest traction control. If that's happening routinely, the real solution is going to be to make the traction better, as with better winter tires.

    Indeed. It will pretty much always be more effective to try to look like one of these guys




    than to polish the ice like this guy

     
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  10. davecook89t

    davecook89t Senior Member

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    That last video makes you want to shift quickly from D to R, as if it was a manual transmission. That's what I did with our 2004 Sable, and had to replace the transmission shortly thereafter.
     
  11. jdenenberg

    jdenenberg EE Professor

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    The ford auto tranny in that era was very unreliable. Almost all of them failed just out of warranty. your Sable tranny failure may not have been your fault.
     
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  12. davecook89t

    davecook89t Senior Member

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    I didn't think it was a coincidence. I did get out of the snow (I guess doing what I did caused it to rock back and forth a little bit, which is what I was trying to accomplish), but it failed a month or 2 later. It was the wife's car, I accepted blame for it, but it was just another failure in a long line of failures on that car.
     
  13. ChapmanF

    ChapmanF Senior Member

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    Not guaranteed to be innocuous in a manual either. I had about 20 minutes of rocking once to get a manual transmission truck out of a plowed-in position. Nothing failed, but the clutch left a strong scent of 'foundry' all up and down the block. (I once lived not far from some foundries; it was that smell.)
     
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  14. pghyndman

    pghyndman Active Member

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    It's been many years, but I recall lightly apply the parking brake to limit wheel spin. I may be wrong, but he lurching seen in the above videos seem to indicate too much throttle is being applied and the car is trying its best achieve traction (ie: spinning too fast = less traction). A case of steady, slow, and easy controls the day, not ooh, ooh, ooh... I'm slipping, better give it more throttle!
     
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  15. m8547

    m8547 Senior Member

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    The parking brake only works on the rear wheels, so unfortunately the parking brake trick won't work on these FWD cars.

    Most people give it way too much gas when the wheels start to slip, then complain about the traction control system cutting power.
     
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