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driving more efficiently

Discussion in 'Model S: Driving Dynamics' started by Ardavan, May 2, 2015.

  1. Ardavan

    Ardavan Member

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    [COLOR=rgba(0, 0, 0, 0.701961)]Watts versus speed
    driving P85D 2015
    [/COLOR][COLOR=rgba(0, 0, 0, 0.701961)]
    [/COLOR]
    [COLOR=rgba(0, 0, 0, 0.701961)]First week into driving this beautiful P85D I have to understand the relationship of the kilowatts with the speed. I have a suggestion for people. I would like to have a more intelligent cruise control system and this is my proposal (this may not be new). I wish I could set the cruise control to speed and watts. In this I could set the maximum watts to let's say 30, and the speed to 72. The car would slow the speed down to maintain a maximum watt expenditure of 30 with a minimum speed limit. For example the speed would never go below 65 let's say on a climb and the watts in this situation would pass the 30 limit, but in general for cruising the maximum speed would be achieved in relation to watts expenditure. This would maximize efficiency. I want to be able to control the watt expenditure and the speed not just the speed. The cruise control should allow me a high and low range and I should be able to set the watts either to a limit (relative to minimum speed) or choose no limit to cruise speed. What do you all think of this? I'm sure I'm not the first person to think of this.[/COLOR]
     
  2. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    This has been though about many times over the past couple of decades. So far not one automaker has stepped up to the plate.
     
  3. Ardavan

    Ardavan Member

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    Thanks. I wonder if now they actually have the technology to do it. I'm sure I'm not an original thinker in this.
    Adaptive Cruise and Adaptive Watts!
     
  4. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Certainly. The major problem is that elevation isn't that accurate with GPS. However, I'm pretty certain that it wouldn't take a large effort to overcome that. It would require more memory and computing power to do so.
     
  5. Ardavan

    Ardavan Member

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    I would like to have a range for the cruise control never going below a certain mph, but at the same time be able to set the desired watts. If need be exceed the desired watts to maintain a minimum speed regardless of terrain. That way you wouldn't have these huge peaks and valleys in your energy chart and I'm guessing the battery efficiency would go up if it was putting out a steady stream rather than sudden bursts.
     
  6. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Right.That's what you do when you manually control the car.
     
  7. Cyclone

    Cyclone Active Member

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    Similar to TACC now where you can auto-engage to the Speed Limit + offset, I would love to have a Cruise Control mode that, absent TACC intervening b/c of radar/sonar/camera, I set a speed with a +/- offset for just this very purpose! So I could say, set the speed to 65 mph +/- 10 and while going uphill it will go down to 55 mpg before ramping up the power. Similarly, going downhill, I will let me get up to 75 mph before ramping up regen. Then it's just a matter of TACC rules applying to following distance that override all the above.
     
  8. BerTX

    BerTX Member

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    It would b nice to be able to have some settings to vary the gain on the cruise control.

    At this point in the maturation of Tesla, one of the most frustrating things to me is the unrealized potential of their being in control of every aspect of the cars performance and passing on the opportunity to make changes like this. TACC should NEVER get into a situation where it has to apply the brakes, for example. There are so many tuning opportunities that are possible to tweak the car that we never see.
     
  9. hiroshiy

    hiroshiy Active Member

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    To save power with TACC, I don't think limiting peak power is the best. It seems Model S is wasting little power to accelerate quickly than slowly. Rather, the most wasted energy seems to be the loss between excess acceleration and regen to compensate.

    Thus to save power, TACC needs to use the car distance as an elastic buffer, not as something fixed relative to speed. For example, if the car speeds up, slowly keep up but always a bit behind the targeted speed. If the car slows even a little bit, coast immediately and see if the distance gets closer. If the distance gets bigger, apply more power. If the distance gets smaller, wait until it gets uncomfortable (get closer than specified) with coast and finally apply regen to regain the specified distance.

    Setting of 1 makes this buffer and base distance small. Setting of 7 will make this buffer and base distance big, thus saving a lot of power by not using regen and instead consuming power only for aerodynamic and tire rotation losses.
     

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