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unintended acceleration

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Discussion starter · #1 ·
This morning, I was running low but the Sunoco station on the NJ Turnpike was out of gas! No problem, very bizzare and rare, but I had 25 miles on the trip computer and was sure there was another gas station on the way.

15 miles later, BAM. Traffic jam on 276 West in PA for like 10 miles. next service station, 25 miles! Car's computer read 0 miles at this point for at least 15 minutes of bumper to bumper traffic.

Fast forward after sweating bullets on my way to an important work conference, I got off an exit, found gas all is good. But, car took 15.4 gallons. Surprising I was sure that I was almost empty. Interesting, quick google search, capacity is 17 gallons. I was sweating bullets for nothing, I had at least 1 to 1.5 gallon left.

Positive now is that I have a much better idea of how far I can go when the computer reads 0. good to know, 0 miles is about 2 gallons left.

But, it's BS. With the technology built into cars today I shouldn't have to guess how much gas is in the damn car.

Why don't cars read out how many gallons you have left in the car on the read-out? Not how many miles to 0. Not a yellow warning light. Not a wildly inaccurate analog display. But rather, a very clear simple display of how many #$ING gallons are in the damn car. Simple. It's all I need to know.

Is it that the general public can't handle this information and interpret it properly? Do car manu's purposely just exaggerate the display and dumb it down for the average Joe? "Hey mr engineer, don't put how many gallons left, people aren't that bright. Just put 0 on the display when there's 2 gallons left" Yeah, good idea.

It would just be super helpful for those of us who aren't retarded and use this information to make our lives easier.

I understand fuel in the lines/pump/injectors wouldn't make this 100% accurate, but a very good guess seems very doable.


I know many of you will argue anything and come up with reasons why this is dumb, but with all the other useless crap in cars this seems like a feature that is helpful to some.
 
Liability as mentioned above.

Also - they hope that when people see a number approaching 0 they will fill up and not have a YOLO attitude. However, if they hit 0, at least they have a safety net on to which to fall back on.
 
Ive had a similar situation with my Jetta. Dropped the car off at dealer for a transmission issue with about a 1/12th of a tank of gas (I guess), gas light came on as I pulled into the lot...figured id just get gas when I pick it up. They gave it back to me with no blocks left on the gauge and range saying 0 miles. Made it to a gas station about 5-10 minutes later after some traffic and a few stop lights.
 
I'm also sure if you dig in the owner's manual, there has to be some language stating something along the lines of "this number is meant to be an approximation and does not portray the true and exact miles left within the tank. Fluctuations may occur due to driving conditions including but not limited to vehicle slope, driver, weather conditions, etc. Driver to use this number for reference only as it represents an approximate estimation within +/- 5% of accuracy."

Something like that.
 
Never had this issue before. I generally fill up once the tank reaches just below half.

I did have a '79 Mark V that would tell you how many miles you had left, that was a neat feature. But even on a full tank it would only read 142. :laugh:
 
Discussion starter · #8 ·
Liability.
I don't see how Audi would be liable for telling you clearly how many gallons are left. I get it though, society today is nuts.

How about an option on my stalk to tell me how many gallons are left, as a usable option or display. top click.. Miles to "0" = x... click... Average MPG ="x.x"

New readout optional display ie... Gallons to 0 = x.


Just another readout? Can I submit a feature request to Audi? haha. It just seems so obvious for many people to have this is an option, thats all.

Maybe there is a tune out there where I can retrieve this data from the display.
 
Discussion starter · #9 ·
I'm also sure if you dig in the owner's manual, there has to be some language stating something along the lines of "this number is meant to be an approximation and does not portray the true and exact miles left within the tank. Fluctuations may occur due to driving conditions including but not limited to vehicle slope, driver, weather conditions, etc. Driver to use this number for reference only as it represents an approximate estimation within +/- 5% of accuracy."

Something like that.
Manual says the reserve is 1.8 - 2.4 gallons when the light comes on, but I don't see how this holds up. It's more like 3 - 4.

Small gripe, but its interesting that a basic function of most cars, even $58K cars when new is so inaccurate.
 
My smart gauge starts flashing at 1 gallon and goes down to tenths after. I have gotten to 0 before and got nervous and got gas within the half mile. I think even the there is a half gallon reserve as I put in 8.5 gallons, and capacity is 9ish. I do like the feature, and I know that I have about 50 miles or so left to get gas.
 
Back in my college days I had an 87 Buick Somerset. Basically a Grand Am with digital gauges. When it got down to 1/4 of a tank you could push a button that made the fuel gauge use the entire gauge sweep as the 1/4 tank. It really let you know when you were about to run out as the car would be on fumes when that last bar went dark. Great for a college student as it frequently had less than 1.4 tank! I don't think I have ever owned a car with a more accurate fuel gauge.
 
Why don't cars read out how many gallons you have left in the car on the read-out?
Why are you sitting at your computer uselessly bitching about it? If you want the gas gauge to provide meaningful information, it's very easy to do--just go out there and run your car out of gas.

I did this once with my '74 Dart Sport. The gas gauge would only go up to the 3/4 mark even when I stuffed it so full that gasoline was running down the side of the car. Figuring the gauge might also be inaccurate at the other end, I decided to put it to the test. I filled my 5gal can with gas, put it in the trunk, and then deliberately drove until I ran out of gas. At the side of the road, I simply poured in my five gallons. Once I had done so, the gauge came up to exactly the E line. So now I knew 'empty' meant five gallons left.

Easy.
 
My Focus is pretty dang accurate. I average about 30-35 mpg depending on time of year. My gas light comes on generally with about 35-40 stated miles left (just a hair above the bottom line). If I fill it up right at that point I generally have just over a gallon (1.2 or 1.4) left.
 
My car seems to be pretty accurate as well. However, my range predictor doesn't go to 0, it reads actual numbers until you get to less than 9 at which point it just flashes dash marks. I guess that's how they get around liability issues.
 
. But rather, a very clear simple display of how many #$ING gallons are in the damn car. Simple. It's all I need to know.
How would you go about calculating this number to a worthwhile precision?

Once you consider all the factors involved... a system based on a time average of a float riding on a sloshing volume of fuel with some safety factors added in is a pretty good method.

Even DTE calculations, which take past and current fuel economy into account still have to reference the wildly inaccurate fuel level sensors.
 
Part of the reason why is definitely to give the owner an extra safety cushion. Running a fuel injected car out of gas isn't a great idea as it will damage the fuel pump. I'd imagine the new high pressure pumps for direct injection are even more sensitive.

I can imagine people trying to get the fuel pump fixed under warranty after they run it out of gas. I just love how people are like "why does the manufacturer think i'm dumb and say i have 0 miles left in my range when there are a whole 2 gallons left?"
Then prove how smart you are by driving it down even lower.

Have you thought about what 2 gallons looks like sloshing around in a 20 gallon tank?
Do you ever go up or down any hills?
Also, I doubt any tanks are set up to draw from there very bottom of the tank as that would result in debris getting sucked into the fuel pump. You'll never be able to totally drain the tank. (Ever cut grass on a steep hill and have your mower die?)

Here are the types of hills we have in my area (steepest in the world pictured below at 37%)
Image


http://en.wikipedia.org/wiki/Canton_Avenue
 
This morning, I was running low but the Sunoco station on the NJ Turnpike was out of gas! No problem, very bizzare and rare, but I had 25 miles on the trip computer and was sure there was another gas station on the way.

15 miles later, BAM. Traffic jam on 276 West in PA for like 10 miles. next service station, 25 miles! Car's computer read 0 miles at this point for at least 15 minutes of bumper to bumper traffic.

Fast forward after sweating bullets on my way to an important work conference, I got off an exit, found gas all is good. But, car took 15.4 gallons. Surprising I was sure that I was almost empty. Interesting, quick google search, capacity is 17 gallons. I was sweating bullets for nothing, I had at least 1 to 1.5 gallon left.

Positive now is that I have a much better idea of how far I can go when the computer reads 0. good to know, 0 miles is about 2 gallons left.

But, it's BS. With the technology built into cars today I shouldn't have to guess how much gas is in the damn car.

Why don't cars read out how many gallons you have left in the car on the read-out? Not how many miles to 0. Not a yellow warning light. Not a wildly inaccurate analog display. But rather, a very clear simple display of how many #$ING gallons are in the damn car. Simple. It's all I need to know.

Is it that the general public can't handle this information and interpret it properly? Do car manu's purposely just exaggerate the display and dumb it down for the average Joe? "Hey mr engineer, don't put how many gallons left, people aren't that bright. Just put 0 on the display when there's 2 gallons left" Yeah, good idea.

It would just be super helpful for those of us who aren't retarded and use this information to make our lives easier.

I understand fuel in the lines/pump/injectors wouldn't make this 100% accurate, but a very good guess seems very doable.


I know many of you will argue anything and come up with reasons why this is dumb, but with all the other useless crap in cars this seems like a feature that is helpful to some.
You just proved that you aren't responsible enough to see the true value, or you would have ran out of gas. That's why.
 
Also, I doubt any tanks are set up to draw from there very bottom of the tank as that would result in debris getting sucked into the fuel pump.
Every fuel pickup is at the bottom of the tank, usually as part of the float/pump assembly.
Starvation can occur when a steep slope, or if cornering forces pull the fuel to the side of an almost empty tank, but even then, it's rare.

As for debris... I'm not sure what people think gets into their fuel tanks, and how they think it gets there. Whenever I hear this, I imagine opening a fuel tank and seeing tree branches and leaves... but then, I remember that the fuel is filtered at the pump, and even the gas cans for my lawnmowers, which are subjected to far worse conditions than my car, are clean and tidy inside after decades of use.

High pressure pumps for Direct injection are local to the engine. This reduces the amount of high pressure fuel tubing needed.
My TDI doesn't even have a pump in the tank, although other cars do have lift pumps in the tank to get fuel to the high pressure pump.
 
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