jamief Posted August 3, 2007 Report Share Posted August 3, 2007 On my 97 A8, the fuel gauge seems to work quite consistently, however as soon as it gets down to the "red area" (i.e. the last 1/4 of the tank according to the gauge), it shoots down very quickly. For example, say I get 100 miles from 1/2 - 1/4, I might only get 10 miles from 1/4 before the needle is right on empty. Is this just due to the shape of the bottom of the tank? Also, anyone ever run their tank dry and seen how many miles you get once the fuel warning light comes on? Link to comment Share on other sites More sharing options...
ant Posted August 3, 2007 Report Share Posted August 3, 2007 my 97 does that too Link to comment Share on other sites More sharing options...
Ska Posted August 3, 2007 Report Share Posted August 3, 2007 Yeah it seems that way doesn’t it but I’ve put that down to my heavy right foot. Don’t even think about running your tank dry , as you’ve pointed out these have a peculiar shape; sort of like a pair of lungs to make way for the rear diff. and Quattro system so these tanks have some corrugated pipes inside that run to the corners to suck fuel from the extreme corners. These can easily break with age and running them dry. Needless to say you’d be left high and dry whilst you still have fuel in the tank, the fix is a new fuel tank which is labour intensive. Even with the tank off the car its nigh on impossible service anything apart from the fuel pump assembly and the balancing pump doo-whacky. Having said all that I got an extra 20 miles on the M40 once yes I know that was irresponsible but there was a big accident on the that road involving some trucks or something and I got lost trying to get around it. Link to comment Share on other sites More sharing options...
thenamesross Posted August 3, 2007 Report Share Posted August 3, 2007 Mine does the same Link to comment Share on other sites More sharing options...
IT_S8 Posted August 3, 2007 Report Share Posted August 3, 2007 [ QUOTE ] On my 97 A8, the fuel gauge seems to work quite consistently, however as soon as it gets down to the "red area" (i.e. the last 1/4 of the tank according to the gauge), it shoots down very quickly. For example, say I get 100 miles from 1/2 - 1/4, I might only get 10 miles from 1/4 before the needle is right on empty. Is this just due to the shape of the bottom of the tank? Also, anyone ever run their tank dry and seen how many miles you get once the fuel warning light comes on? [/ QUOTE ] Having had to empty a fuel tank completely when removing it from a car, I'd say there is about a gallon left when the needle says nothing - however, like Ska rightly points out, it doesn't mean you can reliably suck that whole extra gallon out...... I find the last bit of the tank goes quicker in all 8's, but I must admit the 3.7 we got recently plummeted like stone, one minute loads of fuel, next minute nothing... Maybe a combination of bad design and fault.... (and no, it wasn't a leak...., but we did check! ) Link to comment Share on other sites More sharing options...
jamief Posted August 3, 2007 Author Report Share Posted August 3, 2007 Yep, thats confirmed what I thought, thanks guys. I'd never deliberately run the tank dry btw, just nice to know for emergencies sake! And boy does this thing drink, not helped by the fact I was using a 50mpg Clio just prior to this! Link to comment Share on other sites More sharing options...
Figure11 Posted August 3, 2007 Report Share Posted August 3, 2007 The other thing to be aware of is that the fuel pump must have constant flow other wise its bye bye pump. My LPG fitter was very emphatic about this. If I were to run my tank (petrol) dry and run on gas then I would almost certainly total the fuel pump. Running out of petrol and leaving on the ignition may do this. Mike Link to comment Share on other sites More sharing options...
LostKiwi Posted August 3, 2007 Report Share Posted August 3, 2007 Mine does the same too... Last bit of the red seems to vanish. And on DIS last night it claimed I had 70 miles left in the tank when 40 miles from home. Cruising quietly at 75-80 on the M6 for that 40 miles saw it say zero just before I got to my exit.... So I would guess the tank shape fools all the electronics and not just the guage! Useful to know about the pump there too.... Food for thought there for when I get mine converted.... Link to comment Share on other sites More sharing options...
Ska Posted August 3, 2007 Report Share Posted August 3, 2007 Maybe its because the range is determined using the live MPG values so on the motorway you get loads for your money but when you hit the B roads you MPG values come down as a result of constant on/off the go go pedal. Link to comment Share on other sites More sharing options...
LostKiwi Posted August 3, 2007 Report Share Posted August 3, 2007 Yeah I know what you mean, but in my case the whole 100mile trip (less 5 miles - 2.5 at each end) is motorway. Therefore with 40 miles to go and it saying 70 in the tank and no increase in traffic, hills, speed etc (i.e. on cruise) you'd expect to have 30 miles or so in the tank when you leave the motorway... yet I had 0!!! Seems weird to me... Link to comment Share on other sites More sharing options...
PsYcHe Posted August 3, 2007 Report Share Posted August 3, 2007 My 98 is the same... Runs happily until the red zone and plummets like a stone. That's probably where it gets to the saddle-bag sections and it isn't set up to handle the non-linear drop in fuel. Link to comment Share on other sites More sharing options...
jamief Posted August 3, 2007 Author Report Share Posted August 3, 2007 Seems strange doesn't it.... you'd think in such a well engineered car they would of figured out how to calculate the correct amount of fuel remaining in the tank! Link to comment Share on other sites More sharing options...
cruiser647 Posted August 3, 2007 Report Share Posted August 3, 2007 My 97 A8 did the same, and my A6 does it now. The last quarter does disappear quickly. Lowest I had showing on my DIS in the 8, was 30 miles range. I never chanced it lower than that! Link to comment Share on other sites More sharing options...
showtime Posted August 3, 2007 Report Share Posted August 3, 2007 i filled up the other night with 15 miles range showing & i got 75 litres of super in there! bit of a sting, i try not to think i'll be doing it again in probably less than 300 miles! Link to comment Share on other sites More sharing options...
nikw Posted August 7, 2007 Report Share Posted August 7, 2007 I've seen this before on trip computer equipped Audis - the estimated range is pretty accurate with more than half a tank left, but gets more and more pessimistic once you're below a quarter of a tank. I think it's set up this way in an attempt to 'protect us from ourselves'. My friends' Renault trip computers give up completely at 30 miles remaining! Link to comment Share on other sites More sharing options...
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