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Modified DWL using CC

Discussion in 'Gen 3 Prius Fuel Economy' started by markabele, Sep 7, 2012.

  1. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    I want some opinions on a technique I've been using lately when on longer interstate road trips where the speed limit is 70.

    Essentially I set the cruise control at about 67 or 68 (or even lower if traffic is very light) and let it do it's thing until I reach a long/steep downhill. If I were continuing to let CC do it's thing it would back all the way off to the point of regen. Instead I feather the throttle until the iMPG is hovering between 75-100 (which usually is a little past the midway point on the HSI). In most cases I will speed up a little but I hold it there until the car slows enough for the CC to take over again.

    I find this a good in between of getting to relax a bit on longer stretches but also staying a little interactive trying to boost MPG some. (it also raises average speed a bit as well)

    fwiw I don't know that this technique improves FE that much, I guess that's why I'm posting about it.
     
    #1 markabele, Sep 7, 2012
    walter Lee likes this.
  2. F8L

    F8L Protecting Habitat & AG Lands

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    It depends on the grade and length of the run. If it is steep and long enough to bother with then I disengage CC near the crest and if there is no traffic behind me I allow my speed to drop a little as I enter Warp Stealth Mode. Then I warp stealth down the hill until I feel my speed is about to drop below my CC set speed. Then I re-engage CC and continue on my way.

    I fully allow myself to go faster than my original speed or the speed limit if the hill is that great. CC won't allow that so it is a waste of energy.
     
    #2 F8L, Sep 7, 2012
  3. walter Lee

    walter Lee Hypermiling Padawan

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    Interesting. :coffee:
    The feathering the throttle downhill using iMPG=75-100 a matching metric sounds alot like the hypermiling technique called Super Highway Mode (aka SHM, which often requires a downhill grade to sustain) except you aren't using scangaugeII to do it.
     
    #3 walter Lee, Sep 8, 2012
  4. walter Lee

    walter Lee Hypermiling Padawan

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    What speeds are you using? Can you provide an example?
     
    #4 walter Lee, Sep 8, 2012
  5. F8L

    F8L Protecting Habitat & AG Lands

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    I drive mostly freeway on my commute and usually have traffic around me but rarely are the directly behind me so losing a couple mph is not going to upset anyone.

    E.g. I set cruise for 60mph. As I approach a large overpass I try and assess whether CC is going to cause the ICE to rev high to maintain speed. If I don't think it will then I leave it on and as I approach the crest I disengage it. Then go I to warp stealth. I am always above 50mph in these cases and rarely do I drop below 55mph unless I am following a big rig.

    On the long steep downhill section of my commute I never have CC on. I simply start down the grade at 60mph and enter warp stealth. The grade causes me to speed up to about 70-72mph. There are three dips which create an uphill section. So I stay in warp stealth and hope that I have enough speed to carry me up them without having to leave warp stealth. On hot days this is pretty easy but on cold days tire rolling resistance is not as good so I usually have to start up the ICE to maintain 60mph up those sections. Then I go back to warp stealth down the other side.
     
    #5 F8L, Sep 8, 2012
    walter Lee likes this.
  6. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    One of these weekdays next week I will go out and test out my theory on the open road to see if I find any significant data.

    I would say if it returns a 3+ mpg difference it might be plausible.
     
    #6 markabele, Sep 8, 2012
  7. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    Heading out Monday morning to run a quick test of this. Any parameters that people really would like to see other than the obvious ones?
     
    #7 markabele, Sep 9, 2012
  8. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    So here is my mini test. I will test it again at a longer distance when I have more time/money to waste. ;)

    The test covered a round trip interstate route with the cruise control set at 62. I used no ventilation of any type. The temp was around 68 and there was a strong breeze from the south.

    There were 4 legs of the test:
    1. out using only CC
    2. in using only CC
    3. out using method outlined in post #1
    4. in using method outlined in post #1

    Data

    Mileage was 6.7 for leg 1 and 3.
    Mileage was 6.6 for leg 2 and 4.
    Legs 1 and 3 had a northeast bearing. Legs 2 and 4 had the opposite.

    FE:
    1. 60.1 mpg
    2. 52.1 mpg
    3. 62.6 mpg
    4. 52.8 mpg

    Speed:
    1. 61 mph
    2. 61 mph
    3. 62 mph
    4. 61 mph

    Averages:
    Only CC: 56.1 mpg
    New Method: 57.7 mpg
    2.9% increase

    Observations:
    This route wasn't a spectacular route to try this on and the wind probably didn't help much either but I believe the result to be of enough significance to think that under more favorable conditions this method could really have some merit. Using my new method I tested on this route I essentially only had to press the pedal about 2-3 times during each leg. This makes it very little work for the possible reward.

    Would love to hear any thoughts/questions.


    Below is elevation of route "out"..."in" would just be opposite.
    [​IMG]
     
    #8 markabele, Sep 10, 2012
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