Winter Weather Warning for Prius Drivers

Discussion in 'Toyota Prius Family' started by xcel, Feb 9, 2008.

  1. WriConsult

    WriConsult Super Moderator

    Yes, there are many situations where moderate wheelspin is the only way to get -- or keep -- yourself moving. I understand that excessive wheelspin can damage things, but only when excessive. After all, those of us privileged enough to have grown up in states that required Drivers Ed recall the warnings about transmission damage from careless back-and-forth rocking to get unstuck -- but they taught that technique for a reason.

    By all accounts the Prius' TC is excessively aggressive and cuts power even at a hint of wheelspin. In very slick conditions you can't help but have some wheelspin. And in deep snow (as well as mud and loose gravel) you actually get better traction by breaking the tires loose. Studies have shown ABS to be very detrimental to stopping distances (by as much as 30-40%) in those conditions, because on loose/deep surfaces you can actually stop much faster by locking up the wheels. [This is not true on solid surfaces like wet or dry pavement, hardpacked dirt, packed snow or ice -- then you're better off with ABS].
     
  2. BillLin

    BillLin PV solar, geothermal HVAC, hybrids and electrics

    There _is_ a problem with the traction control because so many experienced drivers perceive there to be a problem.

    The stock Michelin low RR tires on my '04 Solara are useless on certain types of snow. Switching to different tires in the winter solved my problem. If you live where you feel stock all-season tires are not doing the job, consider an alternative set. Wouldn't a few percent loss of FE be worth peace of mind?

    I had traction control on my '01 Olds Alero. It had a button on the shifter to defeat it.

    my $.02,
    cheers,
    Bill
     
  3. neon tetra

    neon tetra New Member

    Is there any difference in the 07 & later models?

    Did Toyota upgrade the TRAC system?
     
  4. Dan

    Dan KiloTanked in post 153451

    Not the only one. I haven't seen snow in 15 years. The only ice I've seen in that period was in my iced-tea.

    <Speculation Disclaimer="I'm a software engineer not a mechanical engineer, so may be real off base">
    I think it has to do with the PSD (power split device). The hybrid drive train has multiple motors all providing power at the same time. The PSD is used to balance those torques against each other and provide a resultant torque to the wheels. If there is no resistance offered by the wheels the MG's may be unhendered in their power delivery dominating the torque balance of the PSD. One of the MG's jobs is to balance this battle. I could forsee that the engineers would have to set up limiting conditions on these equations to determine how much of a battle condition they could balance. TRAC may have been their answer. Which is also why it may be real hard to fix and real dangerous to disable. If part of TRAC's job is to keep the MG's within their mechanical tolerances, this TRAC system is effectively a mechanical and not as software based. No fuse to pull. You'd have to replace the MGs
    </Speculation>

    One thing I'd be interested in is how TRAC behaves in Prius models that have either the EV mod or factory EV. If EV is engaged and your only power device is the MG is TRAC less aggressive in cutting power? I just haven't heard this much noise coming out of Europe and England where I would thing TRAC problems would also present issues. If I recall, all EU and British Prius models have factory EV. Maybe Factory EV means more than hooking up pin 27 ;).

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