Excessive Wheel Spin

Discussion in 'Prime Main Forum (2017-Current)' started by m8547, Jan 10, 2019.

  1. m8547

    m8547 Member

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    Is it just me, or is it way too easy to spin the drive wheels in EV mode? If I accelerate too quickly from a stop the wheels sometimes spin, that's fine. But if I'm accelerating moderately through a turn sometimes it happens. Or if I hit a pothole or a manhole cover while accelerating. Or recently I ran over a single piece of gravel pulling out at an intersection and I could hear that wheel spin, followed by a huge CLUNK as the wheel either regained traction or the ABS kicked in to stop it.

    Why doesn't the motor controller limit the speed of the motors? Or why doesn't the ABS kick in faster?

    I have Blizzaks on right now, so not terrible tires. The problem was similar with the factory tires.
     
  2. schja01

    schja01 One of just a few in Chicagoland

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    What mode?
    Power? Normal? Eco?
    Nit, its traction control kicking in not ABS.
    ABS keeps wheels from locking during braking.
    But you knew that. :)J
     
  3. m8547

    m8547 Member

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    Eco mode.

    It's all the same thing that pulses the brakes, whatever acronym they want to call it. ABS, EBD, TRAC, VSC, ATRAC, auto LSD, DAC, HAC, CRAWL control, etc. (all used on various Toyotas. Other companies have their own set of acronyms). There are just two overall modes of control: Interrupt braking to allow a wheel to keep rotating, or apply brakes to slow a wheel that's going too fast.
     
  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Wheel must slip before slip can be detected and acted on. No practical way for the car to estimate how much traction it has, so all it can do is follow your foot's lead and then be ready to offer corrections.
     
  5. bisco

    bisco cookie crumbler

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    what kine of weather are we talking about? i don't recall reading this complaint ever
     
  6. schja01

    schja01 One of just a few in Chicagoland

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    I’ve noticed some slip on ice (not packed snow) when accelerating but always chalked it up to being normal so never gave it a second thought.
     
  7. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Also, I caught this one:

    Hmm... Turning and accelerating at the same time? In enough winter that you thought to hang blizzaks? I realize that it's subjective terminology but at face value it goes against the most useful nugget of winter driving education I ever found: "Accelerate, turn, or brake: pick one!"
     
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  8. schja01

    schja01 One of just a few in Chicagoland

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    I think accelerating out of a turn is normal.
     
  9. m8547

    m8547 Member

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    The roads are dry right now. Of course I expect to spin the wheels a little on snow or ice, and the traction control actually does a decent job if conditions are slippery. But probably 80% of the winter in Colorado the roads are dry. There's one spot in particular where this happens on my drive home. There's a light that's always red where I stop and make a right turn. There's a manhole cover exactly where my right wheel usually drives. If I don't intentionally avoid it, the wheel will spin a little (or sometimes a lot) as it hits the manhole cover. The turn is at the bottom of a big hill, so I have to accelerate moderately quickly to get up to speed and merge with traffic.
     
  10. bisco

    bisco cookie crumbler

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    potholes and manholes are common prius traction problems. not much you can do but try to avoid them.
    i'm constantly weaving within my lane, (and out of it, if theres no on coming traffic)
    peeps behind me know i'm crazy and hang back
     
  11. juhjuhjuhjames

    juhjuhjuhjames Junior Member

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    Lol, makes me feel better that I'm not the only one who has experienced that CLUNK. First time it happened, I was pulling out of a gas station and I thought something fell off from under my car. Funny you mention the whole EV thing because looking back, the couple times it's happened to me was while on EV mode as well. Wonder if you're onto something?

    Is the clunk exclusively a FWD or Prius problem? I've had mine for less than a year and had a Subaru for the 8 years prior to this, so I'm still adjusting
     
  12. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    When traction control cuts the power in a gas car, it takes a fraction of a second to actually slow down the crankshaft and driveline leading to the wheel. You'd certainly notice the loss of power but it isn't very sudden because it takes time to spin down the works.

    In an electric-drive car? The power cut is going to happen at the speed of light, and the driveline is considerably lighter, so the response you feel is much sharper- a clunk.

    Toyota has gone to some real effort to prevent these cars from getting into a situation where the wheels are spinning until the tires bite pavement. That sudden engagement is hard on any car, and especially hard on electrics. I don't know if they are trying to protect the inverter from the enormous current spike it would likely face in this situation, or if it is to mechanically protect the transmission from too much sudden torque. It could be both.
     
  13. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    The OP is also in Colorado so the only things I will add is that we like to spray granite chunks onto the road for winter traction and they often collect at intersections weeks after a snow. So basically from October through June, we drive on slippery surfaces due to either snow/ice or the granite. I've found with a lead foot the Prius will easily break traction with poor tires on these roads. One of the reasons why I run winter tires the entire year. The soft rubber grips and I can punch it all the time. Tires only last 3 years but it is worth it.
     
  14. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Clearly this was for you.:)

    [​IMG]
     
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  15. jaqueh

    jaqueh Active Member

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    I think it’s from the nanocrappers. Those tires are awful and downright dangerous in the rain. I have 23k miles on the car and they somehow still have 3” of tread left. Next rainy season I’m going with something better.
     
  16. m8547

    m8547 Member

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    What I'm seeing is the opposite. In a non-hybrid car, the engine can't spin up very quickly, so if one wheel momentarily loses traction you might not notice. But in EV mode the electric motor will almost immediately spin up and allow that wheel to spin fast. The speed should be limited by the control system for the motor which could react instantly, much faster than the traction control system which has to physically activate the brakes. But it's not for some reason.

    It's not really a 2WD problem, because as long as one wheel has traction and the engine or motor doesn't spin up too fast, the wheel with less traction won't spin up too fast. The problem is the speed of the electric motor increases too quickly, so the wheel with less traction spins.

    I don't think the clunk is the car cutting power. I could be wrong, so I'll have to investigate more. It sounds like either the wheel suddenly gaining traction or the brakes pulsing to slow the spinning wheel. Most of the time the traction control light doesn't come on, but sometimes it does if a wheel spins excessively. I agree that a shock load to the drivetrain is not good for it.
     
  17. Washingtonian

    Washingtonian Active Member

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    I think what the op is describing is just the instant low speed torque we have available in EV mode compared to what I am used to in all of my previous ICE cars.
     
  18. m8547

    m8547 Member

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    Mine came with dunflops, I think. But I have blizzaks on now and the problem is only slightly better than with the all season tires.
     
  19. m8547

    m8547 Member

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    That's part of the problem, but not totally. It's understandable if I floor it from a stop and the wheels spin because of instant torque. But the wheels also spin if I'm using constant pressure on the accelerator pedal and one wheel hits something very slightly slippery when I'm already rolling.

    Maybe it's unavoidable with an EV. But it seems like the motor could be controlled to not suddenly accelerate if one wheel breaks loose.
     
  20. fuzzy1

    fuzzy1 Senior Member

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    If you've been accelerating on slick manhole covers for years exclusively in a Subaru or other AWD, then suddenly switch to a FWD, you will need some adjustment time.

    I've been driving FWDs continually since 1986, and manual transmission Subaru AWDs continually since 1997. There is very clearly a difference in how these systems handle a single wheel slipping on a manhole cover.
     
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