What am I doing wrong? Or maybe - just can't please some cars.

Discussion in 'Gen 4 Prius Fuel Economy' started by alanclarkeau, Jun 6, 2019.

  1. alanclarkeau

    alanclarkeau Senior Member

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    You just can't keep some cars happy. Samantha had this result earlier today:

    upload_2019-6-6_15-49-18.png

    AND then she grizzled that I could have done better:

    upload_2019-6-6_15-50-22.png

    HOW can I please a car with that attitude? How can I improve on ZERO?
     
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  2. CooCooCaChoo

    CooCooCaChoo Active Member

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    I wouldn't pay too much attention to that indicator. I can get 90 mpg going home from work and still only get a score of 85-90.
     
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  3. The Professor

    The Professor Active Member

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    The first pic is the real indicator of how much fuel you've used on average. The score is a measure of how economical your driving style was. The former is affected by things like the route, weather, driving style, and so on. But the score measures the one thing you have most control over. You. You're not going to get great economy if your route is all uphill, but you can still make the best of that situation via improving your score.

    I get around 95 to 98 on most trips when I'm playing that Prius driving game.

    To get the best scores for acceleration, you need to hold the accelerator where the ICE is running at its most economical speed to power ratio. That sweet spot is right at the very top of the big ECO section (immediately below the red PWR area) on the accelerator guidance indicator. Go into the red PWR area, or any lower than about 90% of that big ECO section and your score will drop. So when starting off from a stop, quickly press and hold the accelerator at that exact position until you reach your desired speed. This takes practice. If you manage that you'll get 98 or 99 every time.

    Don't crash while concentrating on your guages! I mean this. AEB does work on a Prius, as I found out doing exactly this.

    For the cruising score, that measures how much your accelerator pedal is moving while maintaining speed. Pick a spot on the upper half of the ECO section and keep it there and don't move it at all until you need to stop. The logic here is that speeding up and slowing down frequently uses a lot more fuel than maintaining a constant speed. Bang! Another 95 or more. This will be averaged with your acceleration score. The thing to practice here is knowing how much accelerator your car needs to travel at a given speed. Hills and traffic mess this up. Just accept that.

    Now comes stopping. Take your foot off all pedals and let the car gradually allow down to a stop. Don't press the brake until you're moving at a walking speed or less. You should get 95+ here too.
     
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  4. alanclarkeau

    alanclarkeau Senior Member

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    Yep I did that - that's how I did 2.2km without the ICE starting up - hence, ZERO l/100km. But she still wasn't happy. It was a good run, no traffic behind me, so I could ease over the 2 small rises. It still had ½ a hybrid battery when I pulled into my garage.
     
  5. The Professor

    The Professor Active Member

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    Ah, but it knows that purely using EV is not the most economical way to drive in the long term. That power in the battery originated from the ICE and may have been more efficiently delivered directly to the wheels to avoid conversion losses.

    Looking at the scores it was probably mostly due to pressing the brake too early. You've got to slow almost to a complete stop before pressing the brake.
     
  6. The Professor

    The Professor Active Member

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    Happy car...
     

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  7. Salamander_King

    Salamander_King Senior Member

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    LOL. I stopped paying attention to the ECO score long time ago. There are some with feather foot touch who can achieve 100/100 score, but not me. I flunk most of the time, still get good mpg. The other day, I don't know how I did it, but I got 5/100 Eco Score, but when I checked my mpg for the segment, I wag getting 73 mpg. I have no idea how the car scores the test.o_O
     
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  8. The Professor

    The Professor Active Member

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    Post number 3, my friend. A light foot may work for traditional cars, but not a hybrid with an Atkinson Cycle engine in it. It has a very specific rev range where it's super economical (right up next to where the PWR section starts). The hybrid synergy drive computers attempt to keep it within that rev range by augmenting it's power with the electric motor, or using up the excess power to charge the battery. That's where the magic is.
     
  9. Salamander_King

    Salamander_King Senior Member

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    Yeah, I get what you are trying to say. But, but, but... I get Eco score of 65 and 75mpg one day, and for the same segment of commuting drive I get Eco score of 98 and 65mpg following day. I have no idea how the score of 5/100 could end up with 73mpg which is better than most of higher Eco scores. The high or low "Eco" score do not corresponds with either high or low ecology or economy in my user cases.
     
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  10. The Professor

    The Professor Active Member

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    It's because the ECO score attempts to educate people how to drive this type of car economically. It's a generalisation, and an average of 3 scores (4 if you have the climate control scoring on?).

    Let me give you an extreme example...

    Let's say you have to floor it to pull out of a junction quickly right at the start of your journey, which could give you 1 for acceleration. Let's say at the end you forget to slow down carefully as you serve into your drive, and so you have to brake suddenly too, giving you a 1 for braking. But let's say that in between you have a decent downhill cruise for 10 miles, and you get 97 for cruising. When averaged at the end of your journey you'll get a score of 33. That looks pretty bad. But those single acceleration and braking losses won't make much of a dent in your overall mpg because you had an awesome 10 miles of downhill crusing. You'll still get 150mpg or something similarly high, but your score was terrible.

    However, the point is that accelerating like that, and braking like that, isn't the most energy efficient way to drive a Prius, so the lessons it teaches are still valid, even if they made little difference in this instance. What if your journey was all stop/start and you only ever used full throttle and maximum braking? You'd get terrible fuel economy. The scoring system doesn't know the specifics of your journey, so it can't tell you how to make that particular journey more economical. It can only give you tips that apply generally.
     
  11. Salamander_King

    Salamander_King Senior Member

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    OK, I get all the technicalities. But still makes no sense to me if the higher score do not corresponds to more economical results of higher mpg for driving the same segment of roads with very similar conditions day after day.
     
    #11 Salamander_King, Jun 6, 2019
    Last edited: Jun 6, 2019
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  12. The Professor

    The Professor Active Member

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    Sure, but if you took a variety of journeys, with different conditions, you would find a correlation between the score it gives and your mpg.
     
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  13. Salamander_King

    Salamander_King Senior Member

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    One thing I forgot to mention is that my car is PRIME (Prius PHV). While driving on EV MODE, Atkinson Cycle engine does not come into the play for the scoring. I don't know if the scoring algorithms are set differently between HV and EV on PRIME. I may try experiments to see if on different conditions of travels, the Eco scores will have a good correlation with the fuel efficiency. But unless I do this either all on HV or all on EV, I predict the results will be all over. :(
     
  14. alanclarkeau

    alanclarkeau Senior Member

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    I never keep the ECO thingy on the screen while driving - there is the partial one on the HUD. I keep this instead, as it's less distracting:
    upload_2019-6-7_9-34-23.png
     
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  15. alanclarkeau

    alanclarkeau Senior Member

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    That particular drive comprised of no ICE, start with Hybrid battery 7 bars. A/C on, set to 25C, ambient temp 25C.

    1) driving out of the carpark at the shopping centre, no braking, little accelerator as 10km/hr speed limit, ~40 metres;
    2) driving gently up a gentle hill - hybrid battery went from full to about ½, ~550 metres;
    3) gentle braking, would be regen only for roundabout;
    4) around roundabout and down hill ~500 metres, light accelerator once up to speed, battery 7 bars by bottom,
    5) accelerator off to slow down for roundabout,
    6) gentle accelerator to next roundabout ~350 metres, no brake at all;
    7) gentle acceleration to Rt turn, no brake ~200 metres;
    8) gentle acceleration to speed limit (50km/hr) dead flat ground ~400 metres;
    9) gentle braking for Rt turn, but regen only;
    10) ~250 metres to my driveway, downhill coasting only, levels again by my driveway,
    11) gentle brake, regen, for driveway, brake so I don't hit back wall of garage.

    Hybrid battery at end 7 bars.
     
  16. The Professor

    The Professor Active Member

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    That would give you great fuel economy on the journey. Good driving.

    Purely from the the car's scoring perspective, I imagine the score dropped by the amount it did mostly due to touching the brakes at all and the gentle acceleration (alluded to by the tip it's giving you). Touching the brakes, even gently, above something around 5-10mph loses points. Accelerating at a level anything other than immediately adjacent to where the PWR section is on the accelerator bar loses points. And to be fair, anything above 70 isn't a bad score because it doesn't directly translate to actual fuel economy.
     
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