Repost from Reddit; and then a question

Discussion in 'Gen 5 Prius Technical Discussion' started by Paul Gregory, Jul 19, 2025 at 9:43 PM.

  1. Paul Gregory

    Paul Gregory Senior Member

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    Common sense is your friend. The Reddit poster is probably not inaccurately relating his event.

    To repeat myself (to apparently deaf ears) the notion of a freewheeling gear train makes no sense for several reasons; There would be a very noticeable "bump" when the drive wheels are commanded to suddenly spin the gear train to compensate for rotation of the gas engine and/or the drive wheels. The gear train also contains brushless motors with powerful magnets, which don't take kindly to being suddenly forced to spin quickly, especially against a high gearing ratio.
     
  2. Paul Gregory

    Paul Gregory Senior Member

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    I think you are grasping at straws to avoid the actual issue.
     
  3. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Neutral feels very neutral to me. I use it infrequently when parking on a steep hill, to gently roll an angled front tire into contactthe curb.
     
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  4. ChapmanF

    ChapmanF Senior Member

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    There's no reason to think the reddit post inaccurate at all, except in the length of the UI delay. I predict that if we get 20 PriusChatters to go replicate the event, 20 will succeed in replicating it exactly (except observing a delay around 1 second), and zero will replicate seeing a delay of 3 seconds.

    So you're back on these arguments again? Why did you not just continue one of your existing threads where you have made them before? There is nothing in this particular reddit post that pertains. The reddit poster is simply reminding people to be sure they have shifted to N when they think they have.
     
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  5. Paul Gregory

    Paul Gregory Senior Member

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    It's supposed to feel that way, but as we all know, there is no clutch or any other disengagement of the gear train.

    The Prius is meant to drive like a conventional car, even providing that "torque converter creep," when you are idling while in drive. But these things are all simulated by the computer.
     
  6. Paul Gregory

    Paul Gregory Senior Member

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    Perhaps you'd make more headway by doing more than simply denying my rationale for what I have opined.
     
  7. ChapmanF

    ChapmanF Senior Member

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    @bisco, @Mendel Leisk: both you guys have presumably read the copied reddit post in #1 of this thread.

    Irrespective of any concerns Paul has added after quoting it, may I ask what you thought the reddit post was about, after reading it?

    Anyone else who may also have read it, but not commented yet, same invitation.

    It would be great to reach some clarity at least on that one simple point.
     
  8. bisco

    bisco cookie crumbler

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    i don't understand the prius drivetrain well enough to know. i'm so ignorant, i thought the o/p was about putting a prius into neutral.
    i wonder if hobbits website has insight on this
     
  9. KMO

    KMO Senior Member

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    'Suddenly spin?' Do you think something changes speed on a transition to neutral?
     
  10. ChapmanF

    ChapmanF Senior Member

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    Well, all I'm talking about is reading the reddit post. I don't think it's because of ignorance that you thought it was about putting a Prius into neutral, I think it's because that's what it was about. :)

    Did you think that required understanding the Prius drivetrain, or just understanding that you haven't shifted to N unless you hold the lever there till N shows up?
     
  11. Paul Gregory

    Paul Gregory Senior Member

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    As you know, both power sources are connected directly to the drive wheels through a planetary differential. They never disengage. So shifting to neutral can happen at any time; when the car is rolling (at any speed) while either power source is engaged.

    Do you really think it can suddenly go to the drive wheels causing the drive train to suddenly free-wheel without some sort of noticeable bump?

    Of course I don't and I doubt that when shifting to "neutral," all the energy in the drive system could suddenly cause the transmission to freewheel. Brushless motors being reverse-spun against a high gear ratio? Seriously?
     
  12. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Pull-along style automatic carwashes are a regular topic here. Even when you've successfully achieved Neutral, due to the car not being able to charge the hybrid battery (in Neutral), and doubly so if you're listening to the radio, running AC, it's possible to run the hybrid battery down dangerously low. One work around: only use carwashes where you drive in and stop, and the cleaning mechanism, a mechanised archway, rolls along the length of the car.
     
  13. Paul Gregory

    Paul Gregory Senior Member

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    I avoid those push-along car washes, because I don't like them, but I have used them several times without any problems. In the car wash, I heard my gas engine start up, with no perceptible bump at all. My car coasts in neutral, just like any conventional car, but I doubt that it was being pushed along with the drivetrain free-wheeling. That just makes no sense.
     
  14. bisco

    bisco cookie crumbler

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    honestly, idk what i thought. the first couple sentences are very confusing to me. when i pull into an auto car wash requiring neutral, there is a stoplight. it says to wait until the light turns green, then pull up until the light turns red, and then put the car in neutral and remove your foot from the brake.
    the reddit poster noticing the car in front going into neutral is confusing.
    when he says 'breaks', that tells me all i need to know. but i did think the gist was about how to put a prius in neutral.
     
  15. bisco

    bisco cookie crumbler

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    interestingly, the hycam has a conventional looking shifter and goes into neutral immediately. or i should say, i've never noticed a delay in 17 years of driving one.
     
  16. bisco

    bisco cookie crumbler

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    reading pauls question again, i don't understand the question
     
  17. bisco

    bisco cookie crumbler

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    going over pauls reiterating the question in post #3, i don't understand the prius drivetrain enough to answer it.
     
  18. ChapmanF

    ChapmanF Senior Member

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    Yeah, in the models where they've chosen a UI where the lever doesn't bounce back through N after you've selected a gear, they don't write in a time delay for selecting N.

    The key paragraphs from the original reddit post, again, were these:

    In the first paragraph, "I thought I'd put my car into neutral" conveys what the poster thought, and also that it hadn't really happened, so the car was in D still, and went forward when brakes were released.

    In the second paragraph, after shifting to reverse, it was once again not put in neutral, so it went backward when brakes were released.

    In the third paragraph, the whole mystery is solved by remembering you gotta hold the lever at N until N shows on the dash. The estimate of 3 seconds seems a bit off, but everything else in the reddit post is straightforward. Just none of it was about Paul's perennial powertrain questions.
     
  19. Paul Gregory

    Paul Gregory Senior Member

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    I don't feel like stating my case for about the sixteenth time, so hopefully someone will twig on the issue in the ensuing discussion.
     
  20. bisco

    bisco cookie crumbler

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    possibly, but there aren't many here interested in this level of detail