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Tech Question

Discussion in 'Gen 2 Prius Main Forum' started by finally_got_one, Apr 13, 2006.

  1. finally_got_one

    finally_got_one New Member

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    I own an '06 package #3 Prius. One thing that has been rather frustrating at times has been the Consumption screen. This shows average fuel consumption over 5 minute periods in bar char form. That, I understand. My question is: Just how is this averaging done? How many points are used in the average(what is N)? :huh:

    The reason I ask this is because there have been several instances now when the consumption screen has shown a 5 minute average of 0 mpg, and I know that I have moved, albeit only a few hundred feet and very stop and go (mostly stop). Recently, this happened when there was an accident ahead and traffic slowed to nearly 2 mph as only one lane (out of 4) was open. :angry:

    Otherwise, I find the consumption screen helpful in watching my driving habits. It is easy to see the effect of accelerating to get on the freeway versus cruising. And, oddly enough, although the Prius is rated higher in street driving, I get better mileage on the freeway. So far, average mileage (after 5 tanks) is about 49 mpg.
     
    #1 finally_got_one, Apr 13, 2006
  2. madams

    madams New Member

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    Well you weren't really moving much so I'd say that your engine was running and 'Bingo' . I know when I'm in slow traffic AFTER the first five minutes or so that the engine will shut down and I feather the 'go' pedal (Hard to call it a 'Gas' pedal anymore) I run on the motor only. I have gotten a couple of 100 mpg segments that way. Currently I'm averaging 52.9 mpg.

    I am finding if I get up to speed quickly and then ease off the pedal a little the instant mpg indicator shoots up to the 60 to 70 mpg range and pretty much stays there. ( That is in the 'flat' midwest region)
     
    #2 madams, Apr 13, 2006
  3. efusco

    efusco Moderator Emeritus
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    <div class='quotetop'>QUOTE(finally_got_one @ Apr 13 2006, 11:59 AM) [snapback]239176[/snapback]</div>
    First of all, don't pay any attention to the Consumption bars when you're in stop and go traffic or when your speed varies significantly over that 5 minute period. The information during those times is essentially useless...anything averaged over TIME when you're not at a steady speed will give some very strange numbers.

    Next, there's nothing confusing about the 5 minute bar you described. You used a measurable amount of gas over a distance close to zero over a 5 minute period... miles (go with 0.01) over gallons (go with 0.01) = 1 mpg over 5 minutes = 0.2MPG/min---won't even show on the scale.
     
    #3 efusco, Apr 13, 2006
  4. finally_got_one

    finally_got_one New Member

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    <div class='quotetop'>QUOTE(efusco @ Apr 13 2006, 01:22 PM) [snapback]239365[/snapback]</div>

    Yeah, I know. Thing of it is, when this first happened, I had not used a drop of gas at all during the 5 minutes in question. I was in stealth mode the whole time...no ICE at all. I expected 100mpg for that 5 minute period. Makes me wonder if the sampling algorithm used happened to take the samples when I was stopped, which in turn makes me wonder just what the sampling rate is, which in turn makes me question the validity of the numbers to begin with. <_<
     
    #4 finally_got_one, Apr 13, 2006
  5. galaxee

    galaxee mostly benevolent

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    i thought i'd seen someone say that on the 06s what was expected to be a 100 mpg bar showed up as zero.

    but i don't remember where that thread is... :blink:
     
    #5 galaxee, Apr 13, 2006
  6. hycamguy07

    hycamguy07 New Member

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    Ok while on the consumpion screen how accurate is the mpg bar graph next to the regenerated power I get confused with the two..
     
    #6 hycamguy07, Apr 13, 2006
  7. finally_got_one

    finally_got_one New Member

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    Ok, it happened again <_< , under somewhat different circumstances. On the freeway (in traffic...accident ahead), I went a little over .25 miles in 5 minutes. ICE was on sometimes, but realtime MPGs were reading no lower than 50. I was stopped twice, so most of the time was spent slowly rolling (stealth mode) with 100 mpg showing on realtime mpg bar. This particular 5 minute period showed 0 mpg. However, the digital mpg increased. This is no surprise, as the 5 minute averages in the bar graph cannot be used in calculating overall mpg.

    So I want to know...what the heck is going on here? I agree that the readings will not be accurate, but the bar graph is not representative of the digital mpg. Hopefully the mpg data is being sampled more than twice during a 5 minute period! :huh:
     
    #7 finally_got_one, Apr 17, 2006
  8. unruhly

    unruhly New Member

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    I remember the post that Galaxee is referring to...

    It's a divide by zero error. Since you've used no fuel over that 5 minute period, it is: Miles/0 = 0. Had the ICE kicked in even for only a few seconds, the bar would have registered 99.9. I see this phenomenon quite regularly as I EV through my neighborhood coming home.
     
    #8 unruhly, Apr 17, 2006
  9. finally_got_one

    finally_got_one New Member

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    <div class='quotetop'>QUOTE(unruhly @ Apr 17 2006, 10:13 AM) [snapback]240960[/snapback]</div>

    That may very well be so...but the ICE did run during that 5 minute period! Well, I would think (being a computer programmer myself) that the good folks at Toyota would have thought of that eventuality and programmed appropriately...oh, well! :)
     
    #9 finally_got_one, Apr 17, 2006
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