Which acceleration from 0 mph has the highest MPG?

Discussion in 'Gen 3 Prius Fuel Economy' started by lexel, Jan 21, 2015.

  1. lexel

    lexel New Member

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    Assume the following situation: You stay on a traffic light, no cars in front or behind you. The light changes from red to green and you are free to go. The street is flat and you want to accelerate to 30mph. Which acceleration has the highest MPG? Power area, upper ECO area? EV area (lower ECO area)?
    What is your experience?

    Assume the following situation: You stay on a traffic light, no cars in front or behind you. The light changes from red to green and you are free to go. The street is flat and you want to accelerate to 30mph. Which acceleration has the highest MPG? Power area, upper ECO area? EV area (lower ECO area)?
    What is your experience?
     
  2. bisco

    bisco cookie crumbler

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    just to the right of the eco line.
     
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  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Do not spin the tires.

    Above some percentage, (75%?) the Fuel Injection enriches the mixture, burning more fuel.

    All cars get poor gas mileage while accelerating, so get it over with and cruise as long as possible.

    To really save fuel, don't brake. If your lights are timed, find the speed that always gives you a green.
     
  4. 69shovlhed

    69shovlhed Surly tree hugger

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    you get the best mpg when you nail it and get through the next 12 traffic signals before they turn red...
     
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  5. mmmodem

    mmmodem Senior Taste Tester

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    The faster you accelerate without going into PWR is better for fuel economy. You want to reach cruising speed as soon as possible so that the ICE can turn off. Look up Pulse and Glide.
     
  6. bisco

    bisco cookie crumbler

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    just give it the bare minimum of ev, the longer you go without the engine firing, the less gas you'll burn.
     
  7. drysider

    drysider Active Member

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    If you have a ScanGauge, you can try out the various options and see the result using the AVG gauge. It becomes pretty clear that higher accelerations result in lower mileages. I have found that the battery energy is better used to extend the glide rather than accelerate the car.

    I have not found this to be the case. Keeping the power bar just above the ECO line consistently results in better mileage. You can confirm this with a ScanGauge using the AVG gauge.
     
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  8. mmmodem

    mmmodem Senior Taste Tester

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    My experience, I find cruising at just above the line gives best fuel economy but not for acceleration.
     
  9. drysider

    drysider Active Member

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    My post is not really very clear. I meant accelerating with the power bar just past the ECO line, not driving with it there. I always use pulse and glide when driving, even at freeway speeds.
     
  10. lexel

    lexel New Member

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    Thanks for all the answers.
    To get you right: You accelerate in the very low PWR line, correct?
     
  11. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Since the peak EGR valve setting happens at 3,200 rpm, I suspect this is the upper limit of efficient engine operation. Accelerate at any engine rpm equal to or under this what I would use. If you don't have an engine rpm display, accelerate so the power display shows little or no power draw from the traction battery. Energy drawn from the battery in excess of the engine power must be made up later.

    Bob Wilson
     
  12. CooCooCaChoo

    CooCooCaChoo Active Member

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    IMHO, EV mode would be best. But the caveat is that the battery has to be green in order to drive the wheels alone.
     
  13. tpenny67

    tpenny67 Active Member

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    Here's my take: Getting from a stop up to about 30 MPH happens very quickly and doesn't use much gas no matter how you do it, so don't be shy about using the PWR region especially going uphill. This is very efficient in terms of time and traffic flow. Forcing the non-hybrid cars behind you to stay in 1st gear longer is not good for overall emissions and collective MPG.

    At higher speeds, the HSI gauge becomes more realistic and gaining each MPH takes more energy than the one before it (ie, 60 MPH = 4x the kinetic energy at 30 MPH), so there's more MPG to gain by accelerating carefully at higher speeds, and you're not as much of an obstacle to other drivers.

    And while I'm bringing the real world into this, the real efficiency gain of accelerating slower happens when the car in front of you stops and turns unexpectedly (use your signal, a$$hat), and slower acceleration means you won't need to get on the brakes as hard and therefore waste less energy.
     
  14. FuelMiser

    FuelMiser Senior Member

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    I doubt anyone really has hard data on this. Oh wait, this is PriusChat, so of course someone has! But not me, sadly. Obviously, the harder you push the pedal, the more gas/time you are going to use, but you will get to 30 MPH sooner, so it might just be a wash. Anecdotally, I remember reading about a BMW model with a little 'e' in the name that was an early attempt at efficiency. This was probably back in the 1970's. There was a comment that brisk acceleration to a given speed is actually better than a leisurely acceleration. So I'm going to go with briskly accelerating to 30 MPH, maybe at the higher end of the ECO scale, possibly into the Power section.
     
  15. fotomoto

    fotomoto Senior Member

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    My experience has been trying many of the above scenarios and getting "OK" results. My best ever tank was 65mpg overall but I eventually got tired of this game day after day and got a plug-in. Now, I just drive and get infinite mpg (999mpg) or about 130-140MPGe on 10 cent electricity. (y) If I try to "hypermile" it, I can achieve 170-180MPGe around town but like I said I just drive normally now.
     
  16. skayaks

    skayaks Member

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    lexel asks exactly what I've wondered since I got my Prius c: "You stay on a traffic light, no cars in front or behind you. The light changes from red to green and you are free to go. The street is flat and you want to accelerate to 30mph. Which acceleration has the highest MPG?"

    I don't advocate some of the tips Wayne Gerdes suggests, since I feel they may anger other drivers.
    But, he's one of the best hypermilers, and there are a few videos of him on YouTube in which he coaches Prius drivers to use electric power to bring the car up to 16 or 20 mph before kicking off the ICE. Why 16? I have no idea how he arrived at that number.
    Two examples can be found at 3:55 and 11:30 of this video:

    There are other videos from the same Toyota of Yakima Prius drive event where he advocates the same technique.
    I try to use this when no one is behind me after a stop (and the state of charge is up).
     
  17. lexel

    lexel New Member

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    In above video at 5:46 there is a good explanation to start: Start in the lower half of the ECO-range (just below the middle) until 16 mph (Use EV). Than push the gas pedal a little bit more to be between half to 3 quarter of the ECO-range. Thats Wayne Gerdes strategy. No PWR range and not even near the max ECO-range.
    I can imagine that the electro-engine has more torque to get the car moving from 0 mph.

    @drysider:
    Your strategy is completely different to Waynes. Have you tried also Waynes strategy?
    We have total different strategies here.
     
  18. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I would have more confidence in any proposed method if there were miniVCI recorded metrics. In my case, the EGR valve settings were recorded as a function of engine rpm. So it turns out 3,200 rpm is one of those 'knees in the curve' where one side is sweetness and roses and the other side is Dante's Inferno. But not everyone has engineering metrics.

    In like fashion, if only using existing Prius instruments, power flow arrows provide a reasonable approach to minimizing how much charge has to be put back in the traction battery. The round-trip has at most 92% * 92% or ~84% round trip efficiency:
    • discharge during acceleration - losses in traction battery resistance and inverter/motor overhead
    • charge after reaching 30 mph - losses in traction battery resistance and inverter/generator overhead.
    There is one exception, the 45-55 seconds it takes for catalyst warm-up when the control laws try to maximize traction battery operation. In this short interval, modest acceleration to 35-40 mph is possible followed by an "N" glide while the engine reaches efficient fuel trim and operation. This has also been miniVCI mapped. But the original poster did not indicate it was a 'cold-start' 0-30 mph acceleration.

    Bob Wilson

    ps. I always prefer engineering approaches with reproducible metrics.
     
  19. drysider

    drysider Active Member

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    I have not tried his method. It will take some time to see if it is better, especially since it is still cold up here. I reset the trip meter at every fill-up, and with about 200 miles on the current tank I am at 55.5mpg. That is with studded snow tires, no grill blocking and temps in the mid twenties (F). Mostly surface roads, of course. Maybe 20% freeway.
     
  20. lexel

    lexel New Member

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    A Scan Gauge has been ordered. Now i have some test ideas.
     
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