[WARNING] Running out of gas

Discussion in 'Prime Fuel Economy & EV Range' started by bwilson4web, Jan 30, 2017.

  1. schja01

    schja01 Active Member

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    Running out of gas causes the fuel pump to cavitate. Not good for a pump.
    For those of you who didn't get the Toyota Platinum Service Agreement
    Toyota Prius Fuel Pump Replacement Cost Estimate
    J
     
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  2. bisco

    bisco cookie crumbler

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    not for the faint of heart
     
  3. EazyPeazy

    EazyPeazy Junior Member

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    Hi Bob, On an unrelated topic, what year is your i3, and just for kicks, what do you think of it? How does it compare to our primes in terms of ride quality and internal noise levels. Just a few questions. Thanks.
     
  4. bwilson4web

    bwilson4web i3 and Prime

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    In hot weather, our 2014 BMW i3-REx has become my daily driver because of the liquid cooled battery and easy EV range:
    • ride quality - shorter wheel base it can be a little 'rocking horse' on roads with joints. Otherwise the Prime is more American 'boat' while the BMW is European precise.
    • internal noise levels - with 168 hp, rear wheel drive, the windows up it is very easy to exceed the speed limit at higher speeds. The Prime is more lethargic getting to speeding mph. Neither has as much of the 'Strum und Drang' of ordinary gassers.
    • EV range 25 or 72 mi - in Huntville AL, the 25 mi Prime is a 'three stop' EV while the BMW is a ten stop car. The last stop is at home to charge.
    More details at: Why the BMW i3-REx | PriusChat

    Let me suggest any follow-up questions be added to the above thread and I'll be happy to share my experience and suggestions.

    Bob Wilson
     
    #44 bwilson4web, Jul 26, 2018
    Last edited: Jul 26, 2018
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  5. EazyPeazy

    EazyPeazy Junior Member

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    Thanks Bob for your response. Just wish the prime had a little more EV range is all. The characteristics are so different between modes for me. Cheers!
     
  6. fuzzy1

    fuzzy1 Senior Member

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    Bob Wilson's various engineering & curiosity tests in his three Prii involved more than 50 intentional out-of-gas events. I wonder how he could afford that many fuel pump replacements? ;)
     
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  7. Prodigyplace

    Prodigyplace Senior Member

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    Perhaps, if we ask nicely, we can convince @bwilson4web to reveal his gold mine :D
     
  8. bwilson4web

    bwilson4web i3 and Prime

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    The original fuel pumps were mounted somewhere in the engine compartment or external to the fuel tank. There was never a question of them overheating because the air and mount handled heat dissipation.

    The amount of gas being pumped to the engine is too small to dissipate enough heat unless the pump operates in a vacuum. Even if some fraction returns to the tank via the pressure regulating spring-valve, it still won't be enough mass to cool the pump.

    The earliest, in-tank fuel pumps may have been thermal sensitive but the mounting to tank with a good heat path to the wall avoids the risk of a warranty replacement. Then the pool of un-pumpable gas remains as a fluid to help condense the heated vapors on the interior wall of the tank.

    Finally, an unloaded pump will turn faster, reducing the electrical load because of the back EMF. So the heat dissipated is reduced. Don't forget that when the car is out of gas, they tend to be turned off.

    'Low gas in tank can overheat the in-tank fuel pump' is an urban legend not supported by even the simplest engineering analysis. However, it is a great way to get people who drive around near "Eh" to keep their tanks filled and avoid running out of gas at a bad place.

    Bob Wilson
     
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  9. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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  10. Prodigyplace

    Prodigyplace Senior Member

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    #50 Prodigyplace, Jul 26, 2018
    Last edited: Jul 26, 2018
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  11. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    My business card now says, "If it can be done indoors, sitting down, I volunteer." I drive folks around MS. Airports, Dr exams, surgeries, etc.
     
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  12. Guy in WNY

    Guy in WNY Junior Member

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    So, from reading this thread, I will NOT be running my brand new - well, 4 weeks old now - Prius Prime oog on my way home from work today to try and get 1000 miles on the very first tank of gas it's ever had. I am at 988 miles right now, the gas pump icon came on at about 925 miles IIRC, that was the day before yesterday. My commute is 42 miles, so I run all the way in to work on electric only with a bit to spare, right now it's at 7%. I tossed the gas can into the back this morning but there's only about a half gallon in the can. It's a 5 gallon can, so I COULD put 3 gallons in and have room to spare, but I think I'll just fill'er up. Go right to the station from here and fill'er up. Don't want to be resetting any computers.
    Guy
    KC2PMM
     
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  13. hill

    hill High Fiber Member

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    The notion that the display still shows traction pack 'usability' is intriguing. It sounds as though the low end (un-accessible) buffer is being displayed as usable - which seems disingenuous on the part of Toyota setting it up that way. When our plug-ins show we're on the last of that last bit 0 juice ... you can be darn sure the 2 cars really really mean it. The most untrue state comes with the Tesla. Our X, when it hits "ZERO" (0 miles) on the display - you still have a teeny bit of very low power slow speed movement left. Better that - than scratching your head in the fast lane, because the car lied to you, displaying you had another mile when you don't.
    .
     
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  14. EngMarc

    EngMarc Member

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    I've written about this to Toyota back in like 2014.
    My prior car a SMART For Two Cabriolet had a VERY accurate fuel gauge that would at about 1 gallon left start counting down in 10ths of a gallon until it hit 0.0. Talk about fraying ones nerves. However, at least you knew where you stood with the fuel in the tank.

    Then, I get the Prius and find the fuel gauge really only has a few meaningful readings: Full, Empty (which really isn't accurate to more than a few gallons. I found this out not by running out of fuel but rather reading sites about using the ODB data to know exactly how much fuel was in the tank - you can't on a Prius as the tank and gauge are NOT calibrated!

    Just another piece of evidence that the Prius does a few things well but most everything else is just thrown on it (a hack) to make a well rounded product launch sell (see my other posts of poorly maintained engine temp issues).
     
  15. bisco

    bisco cookie crumbler

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    what was their reply?
     
  16. schja01

    schja01 Active Member

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    In my flying days I learned that GA (private) aircraft are required by the FAA to have fuel guages that only need to be accurate when on Empty. Any reading other than empty could legally be a crap shoot.
    Unfortunately running out of fuel at 8000 feet has more consequences that at ground level.
    I always keep half a tank minimum. Old habits ...
     
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  17. triggerhappy007

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    I always drive until my range is - - - .I found that means I have around 1 gallon left. I have never ran out of gas. But just be sure you have at least some battery left so you can make it to a gas station.
     
  18. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    I better hit "unwatch this thread"; this talk is driving me nuts, lol.
     
  19. CraigM

    CraigM Active Member

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    Fond memories of the olden days!

    I earned my private license in 1967 in a Piper J3 Cub. The fuel tank, and filler cap, was directly in front of the pilot and in your line of sight. There was a thin rod (think straightened coat hanger) that poked through the filler cap and had a cork on the bottom end that floated on the gas. If you saw a foot of rod sticking up through the fuel cap, you were good to go. If you only saw an inch or two of the rod, you better be on “short final”!

    Personally, I always physically checked the fuel level before flight by sticking a finger into the tank. If it came out dripping gas you were full. No electrical system, so no gas gauge, radios or lights!
     
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