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Inconsistent behavior when switching from R to D or D to R

Discussion in 'Model S: Driving Dynamics' started by pgiralt, Apr 14, 2015.

  1. pgiralt

    pgiralt Active Member

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    I've had this problem happen to me a couple of times now and I can see someone getting into trouble unless the behavior is modified.

    On a couple of occasions, I've been going reverse to back out of a driveway, then shifted to D and immediately hit the Go pedal again, only to be lunged backwards instead of forward. The lunge is followed by the triple beep error tone telling you something is wrong (because I guess it thinks I'm going too fast in reverse to shift to D), but there is a bit of delay so by the time you hear the beep beep beep, it's already too late because you're accelerating backwards. It's not a huge delay, but enough that it's too late.

    I've tried the same thing while going forward to see what happens if you go hit R and the results are inconsistent. Sometimes you end up in Neutral, sometimes you just stay in Drive. It seems like most of the time you stay in drive with the triple-beep (which is not accompanied by a message on the screen BTW). I've made sure when I'm trying this that I press it all the way so that I'm not accidentally going half-click to N, so I'm not sure why I sometimes end up in N and sometimes not.

    I'm pretty sure this wasn't always the case. I seem to remember that if you would shift to a direction the car didn't want you in, you'd end up in Neutral, not stay where you were. Am I going crazy or has this changed?

    I really think the behavior should be to shift to N if it doesn't want you changing to the other direction.
     
  2. dirkhh

    dirkhh Middle-aged Member

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    I've had this happen to me all the way back in 4.4. When rolling backwards down my drive way I seem to naturally end up right at the speed where sometimes it lets me shift to D and sometimes it doesn't. So I don't think this is new.
     
  3. Cyclone

    Cyclone Active Member

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  4. pgiralt

    pgiralt Active Member

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    Ouch! I think I'll report it to my SC to see if they can at least track it and get a response from Engineering.
     
  5. CHG-ON

    CHG-ON Still in love after all these miles

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    I had it happen once. But I think I didn't shift it correctly as I wasn't really paying attention to it. Now I make sure to glance at the speedo to confirm.
     
  6. green1

    green1 Active Member

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    I understand why it won't switch directions, but seems to me it should at least get it to neutral, that way your worst case is weight of gravity on a hill rather than acceleration in the wrong direction.
     
  7. Zextraterrestrial

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    N would be ideal. I have nearly hit a few curbs in quick 3 pt turn arounds and almost one tricked out racing Porsche :scared:
    beep is way late.
    Left foot braking saved me the last time!
     
  8. scottm

    scottm Active Member

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    #8 scottm, Apr 15, 2015
    Last edited: Apr 15, 2015
    I think there's also a time period in effect here, not just roll speed, that limits the ability to change from R to D or D to R with one big push of the selection.

    Beyond some time limit (since you last changed direction), or roll speed limit, one big push of the selector to the opposite direction will land in N.

    In my mind if I've rolled backwards in R for more than about 5 seconds, and try shifting to D directly, I pretty much expect to only get N. And now the brake foot must go down on the pedal and a retry of the direction selector finishes the job. I've haven't clocked the time, but now maybe I'll run an experiment that I'm thinking so much about it.

    I think the Tesla stated conditions in the manual for putting the car into "gear" (selecting a direction) are: foot on brake, car stopped, use the selector in any way you want.

    But there are 'fuzzy' cases where you can change the selection when these strict conditions not being met. These are put there for user convenience, in parking lots with lots of back and forth, etc..

    And when there are exceptions, there must be some conditions to limit the fuzzy logic and put back into place the strict conditions for allowing direction selection.

    Look at some scenarios.

    Scenario: you're cruising down a lane, regenerating to slow down and come to about 5 km/h or mph crawling but still rolling forward with no feet on any pedals, and you slam the selector all the way from D to R. What should the car do? It would be valid to stay in D (ignore your request completely BECAUSE foot is not on brake). It might be valid to change to N (semi-satisfy your request but NOT GO INTO GEAR because your foot is not on brake, but N is "neutral" or nothing, it doesn't connect power to the wheels. A grey area). It would not be valid to change to R (safeguards are needed to prevent accidental stalk bumps suddenly changing the driver's conception of what direction should be connected to the go pedal... what might be used here is a measure of how long it's been since driver last selected a direction).

    Repeat the experiment. But as you're slowing to a crawl and still doing 5, put your foot on brake pedal slightly pressed.... enough for the lights to be on. While still rolling move selector to R. What should happen now? Your foot is on the brake (condition met) but car is not at rest (second condition for gear selection not met). There's a case to be made that you should get any of the following D or R or N. My guess is stays in D, or maybe get N. I would be happy with either. I would be unhappy to get R, I'd want this guarding from accidental shifts, or from accidentally confusing the wiper washer stalk... which I've done.

    Take this further, what about selecting P (park) while rolling? I think the official conditions are the same as gear selection. Tesla would say car stopped, foot on brake. But fuzzy parking is allowed too, I've done it.

    Ever tried pressing P button while driving at a good clip down the highway? I have. (Mixing it up for the ww washers because my other car has opposite stalk placement.) What should happen in this case? Should the car slam on the parking brake at speed? No, it doesn't, it beeps in error. (Or at least it used to beep on 6.0.) Now, I think it may do nothing not even a beep since new software.. I've done it more than once over time..

    Repeat, at a crawl rolling at 3 speed (your choice of km/h or mph), and press the P button on the selector. What should happen? Strict criteria of selecting P are not met... but if the car is rolling slow enough, then yes the P brake clamps and the car lurches to a stop. How fast can you be going to get away with that? Is there a difference rolling backwards versus forwards? Dunno, experiment #12 required.

    What ALWAYS works for ANY gear or Park selecting is: foot on brake, car stopped and not rolling, select a direction, neutral, or Park. And you get what you ask for.

    It's only a convenience that you can sometimes flip from one selection to another, but there are conditions.

    Get to know them if you're going to use them!
     
  9. mknox

    mknox Well-Known Member

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    In over 2 years, the only time I've ended up in the wrong gear was when I didn't flick the lever past the indent and wound up in neutral instead of either D or R.
     
  10. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    5 mph seems to be the threshold, at least for D->N and N->D changes, before brake pedal is required or not.
     
  11. rdrcrmatt

    rdrcrmatt Member

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    THIS. There's nothing fuzzy about it.

    5MPH or less, give the lever a FULL THROW and you'll be in the other gear.

    a Half throw and you'll need to be on the brake pedal at lower speeds to get back into gear. Don't have to be stopped, just have the pedal pressed a little.
     

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