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Going down a hill

Discussion in 'Gen 2 Prius Fuel Economy' started by FirstFlight, Feb 26, 2011.

  1. FirstFlight

    FirstFlight Member

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    When you are going down a hill, is it better to (for MPG purposes):

    a. Do not press the gas or brake and just coast

    b. Gently press the brake (I am only assuming that just tapping the brake will do regen only)

    c. Press the gas lightly so no arrows are going either way

    Also, I've been reading that the scan gauge helps increase MPG. Why?
     
  2. richard schumacher

    richard schumacher shortbus driver

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    c. is best for MPGs. Of course, never let your speed get out of control.
     
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The scan gauge merely gives you better information, it would be up to you to make that into better mileage.
     
  4. BAllanJ

    BAllanJ Active Member

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    For instance instead of going for no arrows on the energy screen, I have my scangauge show me the current out of the traction battery and I just set the gas pedal to minimize the current (not positive or negative by more than an amp or two) when gliding.
     
  5. BrettS

    BrettS Active Member

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    C is best for the best fuel economy because regenerative braking is lossy... you'll still lose some energy in the process. So, if you can avoid doing any regenerating at all and use the momentium you gain going down the hill to keep going forward without using any power then you'll get the best mileage.

    However, it may not be the best option in every situation. If it's a very steep hill then using a and b (as needed) to keep within the speed limit is best. If you know you'll need to stop at the bottom of the hill because of a toll or a traffic light or whatever, then using b to gradually slow down well ahead of the stop would be better than doing C down the hill and braking hard at the bottom.
     
  6. dogfriend

    dogfriend Human - Animal Hybrid

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    Momentum. Momentum. Momentum.

    Get it, keep it, and watch out for momentum thieves. :madgrin:
     
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  7. uart

    uart Senior Member

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    It really depends on how steep is the hill.. Some have mentioned the importance of keeping momentum and of the inherent losses in regeneration but there is a flip side to that coin. The higher your speed the more energy is wasted in wind resistance and this can be very significant at higher speeds.

    For that reason I think another strategy could be better. I think that near the top of the hill it's best to make use regenerative braking to keep the speed low and some time towards the bottom if the hill move to the glide state (no arrows) just in time to allow your speed to rise to the target level for traveling on the road in question. Obviously I'm assuming you're the only car on the road here, what's optimal for energy conservation and what we can get manage without annoying other drivers are two different things. :)
     
  8. 2009Prius

    2009Prius A Wimpy DIYer

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    Wow talking about dedication! How much harder is it to maintain zero current than to maintain the traditional "no arrow glide"?
     
  9. BAllanJ

    BAllanJ Active Member

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    Well it's more that I like keeping the bar graph display and don't want to flip back and forth from screen to screen. Also, I've mounted my SG right above the steering wheel at 2 o'clock so it's closer to my field of view. Having the battery current displayed also allows me to brake without having to switch to friction braking. Also, the arrows don't show you how far from balance you are but the numbers do.

    I display rpm, ign (those two help find the shm and i pulse at 2000 rpm or so too ) engine coolant temp, and battery current.
     
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  10. xs650

    xs650 Senior Member

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    I wish there was a Glide option to go along with the Eco,Normal,Power modes. A button you held down on the steering wheel for Glide would also do the job.
     
  11. BAllanJ

    BAllanJ Active Member

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    I would love that.
     
  12. uart

    uart Senior Member

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    They have, it's called "N" :D
     
  13. 05hybrid

    05hybrid New Member

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    i always do that, i even try it on the freeway :)