The Age-old question

Discussion in 'Gen 2 Prius Fuel Economy' started by WilDavis, Oct 19, 2021.

  1. WilDavis

    WilDavis Senior Member

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    I was wondering, and should know the answer by now, but does anyone know the original sorry excuse/reason why Toyota in their inscrutable wisdom, fitted the Prius Gen II with a flexible bag for a fuel tank? I got caught again this morning when I filled up, and ChuggyPyg burped a couple of pints of Mobil Supreme+ over my feet when almost full. I guess I should learn to pump slower, or stand further away from the car when fueling up! :rolleyes:
     
  2. bisco

    bisco cookie crumbler

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    they wanted a laugh at our expense
     
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  3. vvillovv

    vvillovv Senior Member

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    all jokes aside, I hope your beloved pri didn't upchuck all over your sunday best attire, or working clothes.
    Don't ya hate when that happens. :(
     
  4. ChapmanF

    ChapmanF Senior Member

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    On the upside, when somebody says "those clothes need to be cleaned, pressed, and burned," you're like, "got it covered."
     
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  5. WilDavis

    WilDavis Senior Member

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    Nice one, ChapmanF! The eternal optimist! (Which reminds me: An Optimist sees the glass half-full, a Pessimist sees the glass as being half-empty, and an Opportunist (…such as me) sees the glass, and says "Cor, free drinks! Cheers! BURP!" …which brings us back to the original question… …any ideas?? …anyone?) :whistle::whistle:
     
  6. vvillovv

    vvillovv Senior Member

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    most seem to agree the blatter was used to enhance the EVAP system. Seems to make sense to me. Others might think of it as a safety feature, though probably less likely what the designer intended.
    read more at
    Gas Tank Bladder | Toyota Prius Forum
     
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  7. WilDavis

    WilDavis Senior Member

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    Well, that seems to make sense! (…even at this late hour, so thanks for taking the trouble! (y))
     
  8. vvillovv

    vvillovv Senior Member

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    Sure, anytime WD ...
    I was just whistlin "she'll be comin round the mountain when she comes" the other day. :D and I wanted to know the reason they used the bladder in the gen 2 also. I'd seen a couple of posts about it a few years ago, but none mentioned what it was for, except maybe to throw off the fuel gauge. And of course the burping.
     
    #8 vvillovv, Oct 20, 2021
    Last edited: Oct 20, 2021
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  9. Moving Right Along

    Moving Right Along Active Member

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    It probably has more to do with efficiency than anything else. Efficiency was Toyota’s top priority when designing the car.
     
  10. dolj

    dolj Senior Member

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    As far as I know, it was all about getting the Prius CARB SULEV (or some such acronym) rating. It's always about the emissions.
     
  11. ChapmanF

    ChapmanF Senior Member

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    It's a darned effective system for eliminating the gasoline vapor release into the atmosphere when you fill the tank.

    In an old-skool fuel tank, by the time you roll into the filling station because you're out of gas, you've got a tank with ten gallons of gasoline vapor in it. When you stick the nozzle in that tank and add ten gallons of liquid fuel, you are forcing those ten gallons of vapor out of the tank and right into the atmosphere. Multiplied by the number of vehicles filling up at the number of filling stations everywhere.

    In the bladder tank, the fuel is never anywhere but in the bladder. There's no space for vapor as the fuel is used up—the bladder just shrinks around it. The space in the tank outside the bladder is filled with fresh air. When you fill the tank, the bladder expands, and what gets forced out into the air is nothing but the fresh air around the bladder.

    There is still an ORVR/EVAP system with a charcoal canister and plumbing to mop up what little vapor emission is left over. But by the time of Gen 3, that kind of system had matured enough to meet the same emission targets without the bladder, so Gen 3 just has no bladder and the more complicated EVAP system (which even includes its own little electric pump and does workouts overnight five hours or so after you park).

    There is still ORVR plumbing in the earlier, bladder-tank systems, and if ChuggyPyg is burping fuel on you when filling, it's likely to indicate a problem that can be fixed, and not just the fact of having a bladder tank. (How long have you been driving ChuggyPyg without getting pints of fuel on your feet? The bladder's been there the whole time.)

    [​IMG]

    Some information on getting the ORVR system back up to snuff can be found in this thread.
     
  12. edthefox5

    edthefox5 Senior Member

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    Same reason they went crazy on the cat….emissions.
     
  13. ChapmanF

    ChapmanF Senior Member

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    I hope @WilDavis won't miss the point that if the car has had a bladder fuel tank for a dozen years but just burped fuel out this week, that's probably not so much because it has a bladder fuel tank, and more because an issue in the ORVR system has probably developed and can be fixed.
     
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  14. WilDavis

    WilDavis Senior Member

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    I take your point, and I think the burping issue might well be something to do with me trying to squeeze in the very last drop of fuel in the last couple of fill-ups, something I rarely do!. However I never really understood exactly why Toyota decided have Prii carry their fuel around in bags (…it just don't seem right, somehow!) Thanks everyone for the information, at least now I have no excuse! :rolleyes:
     
  15. Another

    Another Active Member

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    The bladder is another horrible solution to another ridiculous environmental regulation. The charcoal canister system is also prone to repair issues usually about ten to fifteen years into the car life and it costs $1200 to fix on many Toyota or Lexus cars. The cheap plastic on the canister or lines cracks and only Toyota makes the replacement canister. Crap.
     
  16. ChapmanF

    ChapmanF Senior Member

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    There are still photographs that can be looked up showing what cities looked like back when every fillup pushed ten gallons of gasoline vapor into the atmosphere.

    That's definitely not recommended. Overfilling is likely to get fuel into the components that are meant to handle vapor during onboard refueling, and then causes this exact problem. The thread linked to in #11 can be followed for more information on how the problem can be fixed.

    As an example you might not want to follow, the thread involved an owner who had been habitually overfilling, started the thread, spent the money to get the damage repaired, went right back to the same overfilling habits, and started another thread for the same issue less than a year later.
     
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  17. WilDavis

    WilDavis Senior Member

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    Ah, George Santayana applies here, I think: "Those who cannot remember the past are condemned to repeat it" - can also be applied to many other things going on in the world at this moment! :(
     
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  18. Another

    Another Active Member

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    The placement of the charcoal canister that requires many hours to fix a device that routinely and time predictably fails and the use of the bladder tank that is a pervasive and chronic annoyance are flawed solutions for the consumer but great for the service shops and manufacturers. As for the relative contributions to smog from gasoline vapors vs exhaust NOx that is beyond the scope of this thread.
     
  19. ChapmanF

    ChapmanF Senior Member

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    Every car I've ever owned has had a charcoal canister and EVAP system, and so far (knocks wood) I have had zero of them fail ... and I tend to run cars a long time.

    I had a 2001, in all its bladdered glory, until 2016, with nary an issue except the slightly reduced fill capacity in cold weather, which is the only real effect of the bladder when there isn't a problem with the rest of the ORVR system.
     
  20. vvillovv

    vvillovv Senior Member

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    Not always so easy, specially if the car is driven by another/others in the household, whom (not mentioning any names) don't always remember details about what happened yesterday or even 5 minutes ago.:D
     
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