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Hesitation under hard acceleration

Discussion in 'Model S: Driving Dynamics' started by George Jetson, Jan 16, 2017.

  1. George Jetson

    George Jetson Member

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    As a first-time EV owner I am still trying to become familiar with all of the aspects of battery-driven performance. The other day, I was "punching it" when the car suddenly backed off the acceleration a little bit, kind of like when the engine skips in an ICE. There were no strange noises or anything like others have reported here, just a reduction in acceleration after a second or so of full-pedal demand.

    From other posts it sounds as if the computer was limiting the amperage draw to protect the battery; although quite frankly I can't recall the SOC at the time it happened. Does that seem plausible? Any other experiences or opinions on what may have caused this? It's only happened the one time and my car has less than 500 miles on it.

    Thanks.
     
  2. NOLA_Mike

    NOLA_Mike Grouchy

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    Traction Control kicking in? Hit a slick spot on the pavement and the traction control kicked in sounds like the most likely explanation.
     
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  3. George Jetson

    George Jetson Member

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    Would it do that without any tire spin first?
     
  4. jaguar36

    jaguar36 Active Member

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    The car detects very minute amounts of tire slip, so its quite possible the traction control kicked in without you noticing any spin. If it was cold out the car will also decrease available power because of that (you'll see a dashed yellow line on the power graph), although that isn't usually only for a second or two.
     
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  5. NOLA_Mike

    NOLA_Mike Grouchy

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    Yes - as @jaguar36 pointed out the electric drivetrain is extremely sensitive and also has a very fast reaction time (faster than any ICE drivetrain I've ever seen) and is almost imperceptible except for the flashing traction control symbol on the instrument cluster and the slight reduction in acceleration during the slippage. I almost never notice the TC symbol flash because by the time I look down it is done and has traction again.

    There is a whole lot of noise around the forums right now that might unnecessarily concern those not familiar with or who are new to EVs. Please don't let that diminish your enjoyment of the car. I don't see any way from what you describe the computer was limiting anything to protect your battery. I have owned 3 variations of the Model S over the last 3.5 years and each one has been better than the previous one and all of them have been fantastic.

    Mike
     
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  6. Pezpunk

    Pezpunk Member

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    Definitely traction control.
     
  7. vgrinshpun

    vgrinshpun Supporting Member

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    Response time of MS drivetrain is milliseconds, and on top of that torque output can be controlled very precisely. In ICE cars, although engine can reduce output based on traction control system input, it can do it neither fast enough (think about hulk of engine and transmission resulting in huge inertia) nor precisely enough. The fine duty therefore is done by ABS, with the best systems having response time of about 1/10 of a second. Resulting pulsing of the power to the wheels in ICE feels much more ham fisted and violent than in a well designed EV.

    So it is totally plausible for a person new to MS not to notice that traction control got engaged.
     
  8. AmpedRealtor

    AmpedRealtor Well-Known Member

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    If it's traction control you will see the traction control symbol flashing in your instrument cluster.
     
  9. evp

    evp Nerd

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    Sometimes at launch you'll go over one of those white crosswalk lines that are stickers instead of paint. They provide reduced traction for a brief second. Thereafter, all previous comments about traction control apply.
     
  10. George Jetson

    George Jetson Member

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    #10 George Jetson, Jan 16, 2017
    Last edited: Jan 16, 2017
    I had my eyes on the road, not the dash, maneuvering around one of Houston's finest maniacal bus drivers. Silly, I know. These cars are are too darned smart, but it sounds as if the traction control was the most likely culprit. Good to know my car is looking out for my best interests. :cool: Thanks for everyone's insights to help the noob.
     
  11. scottm

    scottm Active Member

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    #11 scottm, Jan 17, 2017
    Last edited: Jan 17, 2017
    Traction control is so good in these cars... I demo it by going into a parking lot that is covered with ice and snow... and come to rest.

    Then floor the go pedal and hold it there while conducting a hard U turn..

    what happens is the car smoothly and slowly turns to go where you want... no drama

    people *expect* a full rear-wheel power slide

    People don't believe the pedal is mashed the whole time, unless you make a show of mashing it and holding it.

    People think you're crazy for trying it, risking flinging your car off to oblivion

    Because it is almost unbelievable that a zero-to-60 monster eater hyper car can also walk with the grace of a cat on a tightrope wire.

    The drivetrain only lays down as much power that can be used in the situation (grip allowing). This is when you realize that the "go" pedal is just a request for speed, and what drive-by-wire really means.


    New EV drivers be careful on the regen side of this equation, which works just as well. Hard regen situations transitioning from good grip to poor grip (icy patch) works the same but in reverse... You'll feel hard regen braking suddenly "let up" and the car may seem to suddenly accelerate or "gain speed" when in fact it's just gone "neutral" and is coasting over the icy patch. Rather than going into the drama of skidding. I forget if the traction light also lights up in this situation. I believe it does.

    Note there is different behavior from when your foot is on the go pedal or the brake pedal. If your foot is on the brakes and you're actively braking when you hit an icy patch - ABS go into effect - chunk chunk chunk! And you'll hear that. The real cool thing is that wheel depending at each corner and which ones are connected to the motor...you can be experiencing a combination of ABS relief *and* regen relief for any wheel at any time in a mix-matched mode ... sounds and "slippage" sensations can overwhelm your senses AS YOU REALIZE YOUR CAR IS CONTINUING TO GO PERFECTLY STRAIGHT. What happen there was like God intervening to drive your car a bit through a tough spot. Blows me away how good this works. And THANK YOU Tesla.

    If you're on the go pedal... the "slip" over the icy stuff happens so fast and silently you won't know what's going on until it has passed... you'll feel a loss in power like a "stall"... and the car may just have saved you from veering into the ditch at full thrust! Awesome.
     
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  12. Pezpunk

    Pezpunk Member

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    hmm, so i take it i'm going to lose if i enter it into any drift competitions.
     
  13. scottm

    scottm Active Member

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    With my car, I can turn OFF the traction control. Dual motor cars can't.

    So I can induce wheel spin on demand, dry or wet payment.

    But the yaw-control and anti-skid stuff still stays put... pretty much killing drift potential of the car, ya.
     
  14. evp

    evp Nerd

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    That turns out not to be the case, although apparently you have to pull some fuses to get the full effect.
    Apparently you can drift a Tesla Model S with the best of them
     

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