[WARNING] Running out of gas (Gen III)

Bob, Would you elaborate on what happened at 185 seconds? Was the the IC stopping because of running out of fuel or just a normal ICE stop?

Was the ICE start at 205 seconds automatic or did you have to tell it to restart?

Have you had problems getting the engine restarted once you added fuel after any of your 4 run to exhaustion tests?

XS650

 

If you are dumb enough to deliberately ignore the clear warnings on the dash board and run out of gas more than once, you desrve what you get.
:wacko:

 

But if you only run out of gas once, you can't graph it.

I enjoy BW's graphs even though I can't imagine anyone associated with Toyota engineering being more than mildly amused.

 

It's called an experiment... He's gathering data to formulate a conclusion... It takes more than once to establish a base line and examine the variables...

Do not try this at home if you don't understand basic science...

BTW, I find this data very helpful, and I'm glad Bob is gathering this data and sharing it with us. I feel much more confident in how my Prius operates and can plan a safe course of action should I ever find my self in a situation where I am extremely low on fuel and unfamiliar with where the nearest gas station may be. Knowledge is power if used wisely...

 

The Power steering fault light is reasonable. Looking at your graph, the DC-DC converter went offline which caused the voltage to fall on the 12V bus. The PS ECU likely detected that it had insufficient energy available for full PS function and set the LED.

I'm amazed that you have no other indication, and this to me is a serious problem! I would expect that we get a christmas tree as soon as the ECM detects engine stall just as in the Previous models.

Bob, can you try this:

While at home, Set the car up so you can pull power to the fuel pump and then do a force charge. What happens the engine dies? This should be a safer experiment, and you'll be able to pay attention to more parameters rather than trying to drive. You will also be able to hear the engine better.

If the car doesn't give you any indication of problems and just loses power, I consider that a safety issue. If this is true, and not just something weird on just Bob's car, I think Toyota needs to consider a software change.

People, this isn't just about running out of gas. I've read page after page of all the silly arguments in this thread tying to get to the useful information, and it wasn't fun. Keep in mind if you end up with a tank of bad gas, or some other problem out of your control (such as a failed fuel pump) this same thing could happen to you, NO MATTER HOW CAREFUL YOU ARE!

I for one, applaud Bob's effort and his willingness to experiment on his own new Prius, as well as at significant risk. I would prefer him to gather data as I've outlined above while motionless in his driveway instead of on a public road, but I think this work is very important.

I think it's downright negligent of Toyota to implement this "silent death" system. All other cars on the road typically get a "christmas tree" when their engines die, and at the very least we should have this in the Prius as well, even if there's no EV capability.

I cannot find any valid reason for Toyota to inhibit EV mode when the ICE dies, as the Battery ECU will not allow the battery to come to any harm. It would run the SOC down to the minimum safe value just as in the Gen2 and the Hybrid ECU would shut you down. People used this "feature" in the 52mph EV mode "hack" which I personally think is dangerous. Maybe this is why Toyota disabled EV mode at ICE fail. Still, if this is true, it's throwing the baby out with the bath water, and it could very well be your baby if you happen to end up with bathwater in your fuel on some busy road!!!

 

I've 'tried'' it twice.

First time in hilly conditions, plenty of time to pull over.

Second, on a downhill, got a good .4 miles - silent running - then at stop light, surprisingly, EV allowed me to limp in to the corner gas station. So I am guessing it is not always black and white (meaning - sometimes EV will allow a bit more movement)...

 

Bob brings more useful data to PC than the vast vast majority of other participants. I enjoy seeing how he is going about getting that data.

 

Re: [WARNING] Running out of gas

I have found that there are almost 3 gallons of gas left in my Prius 1 tank after the single beep [can they spare it?] that indicates that the bottom rectangle on the gas gauge is blinking. That means about 25% of the tank's capacity remains [11.9 gallons capacity].[This car has so many beeps of various pitches and intensities, and all they can give us as a low gas warning is one little peep??!! Give me a break!]

Why can't they design this low gas indicator to let us know when, say, one gallon is left?? One of the things that I hoped would be an improvement over my Avalon was fewer stops for refueling. This idiotic system forces me to refuel as often as I did with the Avalon, it doesn't even have the back-up fuel warning as the Avalon did.

What were they thinking? Is there something wrong with my gas gauge? A major pain, but thankfully the only one I can find!

 

Re: [WARNING] Running out of gas

Do you have trouble reading the fuel level gauge? Why do you need a beep at all?

More fuel equals more weight so the fuel tank was sized appropriately for the car. Most people are fine with a 400-500mile range between fueling sessions. Did you really sign up just to complain about this range between refueling?

A major pain? I'd hate to see how you react when a real life trial pops up in your life....

 

Re: [WARNING] Running out of gas

If any low gas indicator is provided, it needs to trigger with enough warning to reliably get to the next open gas station.

In some of the places I drive, 1 gallon is insufficient for me. Even 2 gallons would be on the hairy edge for some of the anti-hypermilers in ideal weather, let alone foul weather.

This car's fuel range is somewhat better than my best previous car, and far superior to all the rest of them.

 

Bob,

You seem to be the rersident expert here on taking the gas all the way to empty. So my question is, as it relates only to the G3:

- When you get down to one bar on the dispaly, and it begins to blink (is this what you mean by "flash"?), does one have approximately 1.8-2.1 gallons reamining in the tank, and, all that amount is available to run the ICE?

One time I took it down to one bar, and it began to flash...I then looked at the read out to see how many "miles until empty", it read something under 10 miles. I was a bit surprised by that, and had thought that once the bar started to blink/flash, you still had about 2 gallons remaining.

Can you shed some light on this apparent discrepancy between what I thought was remaining, and what the readout displayed.

Thanks.

 

I'm not Bob but have been making observations on guage/warning readings near empty.

First, a little tech...

According to the shop manual, the only fuel level sensor is a conventional float operated variable resistor in the fuel tank. Gauge bar count, start of lowest gauge bar flashing and miles to empty are all computer generated indications of the computer reading that the variable resistor and precessing the results.

Bar count appears to change fairly quickly based on changes going around corners, on hills and stopping, so there is little electrical or computer damping there.

When the lowest bar starts to flash, if it was started by going around a corner, operating on a steep hill, etc, will often stop flashing after 10 minutes or so of gentle driving, so I have concluded that the flash/ no flash condition has more damping (takes longer to change under variable operating conditions).

The miles to empty reading seems to be fairly oblivious to changes in gradient, corners, etc so it seems to be very well damped compared to bar count or start of flashing.

On my Gen3, If I am driving gently and steadily, the bar flash has started at 20 miles to empty the 3 times that I have observed it.

When I fill at start of flash/20 miles to empty the car takes about 9.6 gallons so it looks like I have very close to 2 gallons left at 0 miles to empty.

Just remember, the 0 miles to empty is based on a well damped gas gauge (but it's still just an old fashioned gas gauge sender interpreted by a computer) and there could be any amount of gas left in the tank that Toyota's design goals and manufacturing tolerances allow. So far, people that have been paying attention and measuring carefully tend to have right around 2 gallons left when they hit 0 miles to empty.

 

Exactly what I was looking for! Thanks. :rockon:

 

For the past several months, I've been making a trip of 480-490 miles between fueling.

Usually I have zero bars when I refuel. I have never put more than 9.8 gallons in.

 

I've found as have others that if we pretty much drain it down to not many miles estimated range yet we'll only get in around high 9's, so with the 11.9 gallon tank assuming it can use it all one would assume two gallons or 100 miles once one hits 0. And apparently that's what the data show. To be SUPER SAFE do not drive more than 50 miles after you hit 0. It's a heck of a buffer, actually.

 

Super safe?

While 50 miles is safe enough for most of us most of the time, didn't one of our GenIII readers run dry a mere 7 miles after DTE read 0?

 

Re: [WARNING] Running out of gas

Actually I do have trouble reading it....the display is barely visible with my sunglasses! But that's not the point...The point is that the low gas display triggers long before it needs to! I ran a test...put 2.5 gals in a can and let her run out of gas. I poured in the 2.5 gals and still the little rectangle was blinking!
I don't need that many miles to find a gas station at 50 mpg.


I didn't sign up just to complain about this; I wanted to find out if my gauge was defective or poorly calibrated. Has anyone talked to Toyota about this?

Thanks for the warm welcome to the Forum!!!