Help! Wife stuck on side of road in '06 Prius

I'm proud to take the prize. I hope it is something tangible & useful! (I need a windshield blind). I always like to provide amusement to my friends, as I consider fellow Prions.

I expected the answer to be "no", but not expressed in quite such strong terms. Evidently wisdom is not imminent.

A computer could give a relatively linear output, given the APPROXIMATE shape of the CAR'S bladder (geez!) I am no engineer (evidently) but I suspect there are ways of measuriing the volume of a fill. If the bottom 3 gallons of the gas tank were rigid, sensors like the ones on my camper water tank could determng the residual volume. There is a lack of imagination somewhere. It's hard to believe this car uses a mere float.

You know perfectly well, Jack, that the pump has nothing directly to do with the tank readout: only with with how much it is filled (take THAT!). The CAR decides how to represent the level in the tank. (How DOES it do that?)

Do I get another prize?

Thanks for that .... illuminating ... explanation, Tony: I shall use it often. :lol: Now, where is my astrolabe?

Galaxee, you are a Lady.

C

 

By the way, Jack: you reached the Board's emoticon limit. Are you on Zoloft?

Hehe.

C

 

Now that you understand the bars on your Prius gas (guess??) gage. Now it's time to saftly park the Prius where she will be safe overnight, then walk, run, or call a cab and check the effect of your neighbouhood bars on your bladder. :lol: :lol: :lol:

Oh yea, one more thing Tony forgot to mention, we have no idea of what Haley's comet will have on on your bladder (prius' that is), next time it comes by.

 

Effexor, actually. (And don't feel bad if you think you "smoked me out". I'm no longer embarrassed about my depression; only wish to help others deal with it realistically, and finding the right med is critical and tricky.)

I'm so high on my car I'm inventing new emoticons. That's a problem. I'm mildly manic/depressive, but when the manic part comes I have to secure the roof with eye-bolts. :lol: B)

One-time offer: anyone dealing with/wondering about depression and/or anxiety (I was plagued with panic attackes in the 70's, too) who wants to can PM me if they have questions about meds, coping, whatever. I am not a doctor, paramedic, nurse, midwife, nor do I even mop clinic floors at night. Just a guy who's shameless.

 

1. Au contraire, monsigneur (see below).

2. You get all the prizes you want. And deserve.

3. The guess gauge is the single greatest flaw in the Prius, and none of us can figure out why Toyota can't fix it, any more than Toyota can figure out how to fix it without abandoning the bladder. It has drawn more comment even than
"B", uncomfortable seats or anything except "HELP! Low MPG!".

4. The pump can commonly (and directly) affect apparent MPG (not just in a Prius) by pumping with such excessive force that it causes the automatic shutoff to activate---sometimes several times successively---between 1 and 2 gallons short of the tank being full. Sometimes a poorly-designed filler neck contributes to the premature shutoff, too, and requires slower, manual pumping rather than leaving it in even the "slowest" autofill notch. It's fairly usual for Prius newbies to think their car actually got 42MPG on one tank and 52 on the next, when actually the amount of gas they pumped was the difference-maker

 

I would suggest that if this was the other way around this would cost you a couch, love seat, 2 chairs, carpet and new curtins. Go for it this is worth a new laptop (MacBook?), PDA, and the power tool of your choice.

 

This I do not follow.

1) The Pri does not know how much gas was pumped, interrupted or not. I do by reading the pump. Neither I or the Pri knows what the residual amount was in the tank before pumping.

Neither of us can calculate anything in the short run from the amount of gas pumped. So I don't understand the remark about newbies attempting to determine the gas milage by the tank (computer gas milage approximates this though, because it resets each fillup: it is just not based on the tank volume. THAT's how you estimate mpg "by tank".

2) When does the Pri decide that the tank is full and a) reset the bars to full, or whatever it resets them to? B) reset the mpg calcuator. The first time the gas cuts off; some other signal?

3) The "tank" mpg shown by the Pri is based on gas delivered to the engine, isn't it, not on what fraction of the tank is used? I intend to determine gas efficiency based on the computer, not gas pumped, at least in the short term.

4) The only unknown is the actual amount of gas in the initial tank (which registerd "Full"). I can probably assume it was 10 gal +/- 1gal. As long as I keep meticulous records, that uncertainty will be averaged out and my mpg based on gas pumed will be almost correct eventually.

5) the computer estimate is known to vary from the empirically calculated mpg by a small amount. I don't know the reason for this. Variations in tire pressue might be a reason, expecially if Tire Reset is forgotten.

Oh yes, the seats: I posted a couple of times that you could install a lumbar support inder the seat cover. No-one mentioned that the manual says not to mess with the seat because it can interfere with the side air bag deployment causing SERIOUS INJURY OR DEATH. I have to decide whether to die by airbag or spine.

But I digress.

Did I state anything about mpg that is incorrect?

C

 

lots of people calculate mpg based upon miles driven/gallons pumped on each tank. that's where jack was pointing out the potential for great error. i've given up trying to explain to people why their calculated mpg was way off, noone listens. they just hear what they want to hear, and they feel betrayed that the computer said one thing and their likely flawed basis for calculation said another.

3 gallons is the magic number where everything resets.

calculated vs computer do eventually even out

what else? oh yes. fuel delivered to injectors is what is used to calculate gallons used.

 

Thanks again Galaxee: just what I thought.

I have been reading about this stuff since Oct. I can see where newbies would be baffled by the flexi-tank.

I had forgotton 3 gal is the reset point: so extra gas topping off can make no difference (unless you dum it on the ground). ( I meant dum) and then only in the long-run calculation.

C

 

3 gallons is how much you have to add in order for the tank to realize you've added gas to it and reset the tank mpg calculation and add fuel bars onto the gas gauge.

topping off just puts more gas in the tank, and will set the float higher in its little tube. but there are downsides to topping off- damage to the fueling system and evap system which can be costly to repair.

 

The car doesn't decide the tank is full. If you're not simultaneously watching the guess gauge while you pump, it will even allow you to overfill and spill, without any warning sound. The pump "decides".

I don't know by what mechanism the car resets the MPG. But it WILL reset the guess gauge bars to "full" even if you're a gallon or more short. (Remember, the first bar usually doesn't disappear for +-100 miles. That's 1-3 gal.)

The situation I described can occur for ANY two successive tanks (or even more), thus causing apparent discrepancies---even though the MFD, in these cases, WAS closer to the truth. But people are encouraged, on these boards and other places, NOT to trust the MFD as much as they trust the accuracy of their own hands-on gas-pumping and calculation. (Fact: the Gen 1 MFD routinely produced discrepancies of 3-5 MPG compared to calculated---almost always on the high side. They reduced that error factor to almost nil with Gen 2.)

And, over the long haul, this will yield the most accurate number for lifetime MPG. But many Prius "early owners" can and do get bad calculated readings off one, two, maybe three tanks in a row. THOSE are the newbies who log on and say:

"My MPG is very inconsistent, and

*I changed pumps at the same station

*I changed stations

*I changed brands

*I tried a tank of premium

*I dumped in some additive

*I let the extra air out of my tires

*I switched to synthetic oil

*I think it's the weather

*I think it's because my driving techniques improved (if the MPG "went up")

*I think it's because my (wife) (husband) drove the car for a few days

*HELP! "

:angry:

 

Right. Another dum I forgot to mention, because I was thinking about Jack's mention of premature gas pump shut off. How do you tell if you have a premature shut off or if you'r "topping off"? Experience - or is there a more objective indication?

Also, do the bars go to 10 upon reset at 3 gal, or go up incrementally until the float tells the system the tank is "full".

C

 

To take the last first, the latter. (Got that? )

The only "experiential" way I know is by continuously pulling on the pump handle, squirting in a little at a time, until you see it coming up the filler pipe. Some here will stone me for saying that, as it defeats fume minimization. Otherwise, you can't tell. That was my main point.

OR, to make your head spin a little---and this assuredly happens---you fill up, say, on a cold night with a contracted bladder holding only, say, 10 gal. instead of 11.9. It really IS full. Really, it is.

Next day, voila! it goes up to 80, the bladder distends, you now have an 11.9-gal. tank, but it's got 1.9 gal less in it than you think it has. If it stays distended until your next fill-up, your MPG will have shrivelled accordingly. Tank-by-tank, you can't win, especially in changeable weather. But so far, it's engineered into the car.

 

I believe my confusion is is due to my unscientific use of an anthropomorphism (which YOU encourage). "when does the car think it is full" :angry: I should have known better.

My question really was "when in the fueling process does the computer set the guessguage to 'Full" and does it do it incrementally, presumably based on reading the float level?

When the gas guage reads "full" on a smaller than average volume, I suspect it reads "Full" early because the bladder is not fully inflated (the bladder is in effect, full). If the pump continues to inject gas, it forces the bladder to expand, so it remains full, but at a larger volume.

Suspecting this, I asked earlier about topping off, and Galaxee remarked the guage will [may?] then continue to creep up. There may be two factors at work: a pump may sometimes cut off early before or after bladder expansion is complete. If before, the guage will continue to rise with further addition of gas; if after, it would not. Adding more gas in these conditions would not initially cause the problems Galaxee warned of. But there is not enough information to know when it is safe to add additional gas to the tank (expanding it) unless the guage does not indicate full. :angry:

So it's not only the gas guage that is deficient, but the filling system itself. Personally, I think the latter is the greater probem, because one has to settle for either an unnecessarily incompletely filled tank, or risk damaging the system by topping off in an effort to fill it as fully as expansion will allow.

Maybe the Prius needs a tank heater designed like an electric blanket, which turns on when the gas door is opened, and which warms the inflexible bladder to allow full expansion. If that is deemed too dangerous, one could have a heated oil circulation system, which would unfortunately be more expensive, and heavier.

It's not good to have a variable volume and unknown range gas tank in the West, where distances between gas stations can be large, and not all are desirable. I'd like a display of the gas used when the first bar disappears, which should also permit a reasonably accurate estimate of total tank volume.

The '06 manual, p 320 states that gas capacity is decreased from 11.1 gal to 10.8 at 14F. (I suspect that statement will generate some chuckles ). One could check that if one repeatedly drove the same unvarying route and refilled at constant intervals. B)

C

 

bah, 10.8 gal?? you're right, that amused me.

when it hit the 30s here and i had to fill up, i was lucky to stuff 7 gal in there with the last bar blinking.

i think of it like my last car that had an analog gauge. you know, when you top it off, the gauge goes a little over the full mark. except in the prius, there's no "over the full mark" so it just shows 10 bars for longer. that's my way of thinking. i'd assume that when the little float reached the top of its tube, that would be the signal to put up 10 bars on the gauge.

 

galaxee, has DH ever brought home someone's bladder? Have you seen one in its natural state? (And if so, is that state Arkansas, as its license plates seem to say?) Charles, have you seen your own bladder?

Taking your first conjecture, I don't know exactly of what material the bladder is made. This has been one matter of speculation. Is it nearly as pliable as a thick balloon, regardless of temp? If so, your conjecture about "forcing the bladder to expand" may hold.

If, on the other hand, the bladder is more the consistency of, say, my soccer ball, will it even expand at a low temp, say, freezing or under? Or can it distend only with rising temp? Can/does it fold over on itself at very low volume? If so, does a fold readily undo itself under the weight/pressure of gasoline?

The rest of your post indicates that in a mere 12 hours you've come to almost fully appreciate the complexity of the Prius "gassing up" conundrum. This, in its turn, was the direct progenitor of all my manic little smilies.

Mission accomplished.

 

A little practical advice that has nothing to do with filling your car with gas.

In the interests of marital harmony, you must never state that it was your wife's fault. You may love your car, and not want to disparage it, but the results of blaming your wife instead of your car will cost you far more than a towing bill.

Repeat after me: "It was the car's fault." "It was the car's fault." "It was the car's fault." "It was the car's fault." "It was the car's fault." "It was the car's fault."

 

hah :lol:

haven't seen one myself, but i've read in the tech literature that it's some kind of resin. i don't think it can fold on itself, it just contracts a bit to reduce the area in which vapors can reside as the level of fluid gas in the tank drops.

that said, i put in 8.5 gallons just this afternoon and spilled all over the damn place :angry: there goes my yearly emissions, and it's only january!

 

"Charles, have you seen your own bladder?" No, but I had a colonoscopy once, and saw my appendix on the monitor. :lol:

"in a mere 12 hours you've come to almost fully appreciate the complexity of the Prius "gassing up" conundrum." I'm just smart that way. B)
"Mission accomplished" Thank you, Jack. I feel educated now.

It is almost certain that the bladder becomes less pliable with decreased temperature, which is why you can't force much gas in when its cold. It does not need to be pliable for emissions control because the vapor pressure of gasoline is low at low temperatures.

When it is warmer, the bladder evidently becmes more pliable, and can stretch to accommodate more gas, but not enough to allow gasoline to vaporize much (a physical chemist would probably say that the elasticity of the bladder is sufficient to oppose the vapor pressure of the gasoline.) That may be why it may need some "persuasion" to reach maximal capacity; A powerful jet of heavy gasoline would tend to further expand the bladder. It cannot not reach "flabby" at normal temperatures because it would not be able to perform its vapor containment function (all my interpretation). I don't know what happens in Death Valley. I doubt emissions are tested by EPA at such extremes, so Toyota doesn't care.

It would really be nice to have a replaced bladder in order to explore its properties at different temperatures.

Galaxee, is the bladder encased in a metal tank? If so, one could in principle adhere a battery or block heater to it in climates where one "plugs in" when parked, perhaps, and so get a warm fill up. With a cable hanging out the front even more folk would think it an electric car.

There must be more info on the Prius tank on this thread than anywhere else!

OP, your wife should be gratified at the interest and thought she provoked; but she should be made to read it too. Then she CAN blame the car.

C