Fuel gauge/DIS

[martian]

I was looking at the S4 thread about fuel consumption etc and I wondered if anyone else encounters the same problem as me:
when I run with Optimax I never get more than 250 miles for my 82 litres- but on fill up the DIS will indicate 380 plus miles. After the first 1/4 tank I will still show 350 plus miles and then somewhere or other the gauge/DIS loses the plot. I got to my office the other day with 240 miles on the trip gauge and 60 left on the DIS. I thought it was suspicious and when I started up that evening I had only 5 miles left as opposed to the 60 I had when I turned it off that morning.
I had to be recovered to my dealer two weeks ago after the RAC diagnosed fuel pump failure.According to the RS specialist at Audi I was 'out of petrol'.
Just wondered if anybody else had had similar occurrences? [img]images/graemlins/confused.gif[/img]

[Jon]

yes but in my s3...was a faulty sender

[JohnW]

If the gauge is reading high then maybe you do have a sender problem as the miles left will be calculated based on the senders' output combined with the current fuel consumption.
If you go along the motorway as 70 in top see what it says, then drop 2 gears and clog it and see what happens to the figure [img]images/graemlins/grin.gif[/img]

On my trip to work this morning it was showing 260 miles left. Then I had to slow down for some traffic and it went up to 340, but after they got out of the way it came back down to 270 again.

btw, I have done over 20 miles after the DIS shows I have 0 miles left. Even then I still had a couple of litres of petrol left...

Cheers,
John.

[martian]

Guys thanks for this but the 'miles left' in the tank seems to be worked out on the AVERAGE consumption not current (is that right?) so IMO the overall gross mileage (trip comp plus DIS)should be fairly accurate- my problem is it's anything but. The sender does seem likely as the cause [img]images/graemlins/frown.gif[/img] [img]images/graemlins/frown.gif[/img] [img]images/graemlins/frown.gif[/img] and I'll get it checked out next time I feel like being without the car for 3 days [img]images/graemlins/shocked.gif[/img]

[peterb]

On all my Audis I have found the 'miles to go' information is initially over-optimistic, but the RS6 does seem to be worse in this respect. I wonder whether the 82 litre tank of the 4.2 cars is a significantly different shape to that of the other A6 models, and the DIS/senders do not take account of this.

I have also found that on a couple of occasions I have put the RS6 away in the garage, at the end of a long journey, with the fuel gauge in the middle of the red section, and the DIS indicating 30 miles to go. The next time I start the car, the pointer doesn't move off the end stop, and the DIS reads zero miles to go!

BTW, I have just arrived back from a weeks holiday and the DIS is indicating average consumption of 23.4mpg! I must do the calculations from my fuel log and see what the real consumption is.

[peterb]

the 'miles left' in the tank seems to be worked out on the AVERAGE consumption not current (is that right?)

I believe that the 'miles left' is based on a short-term rolling average (over the last 10 to 20 miles?).

[martian]

I have also found that on a couple of occasions I have put the RS6 away in the garage, at the end of a long journey, with the fuel gauge in the middle of the red section, and the DIS indicating 30 miles to go. The next time I start the car, the pointer doesn't move off the end stop, and the DIS reads zero miles to go!

That's EXACTLY what has been happening to me [img]images/graemlins/confused.gif[/img]

[peterb]

BTW, I have just arrived back from a weeks holiday and the DIS is indicating average consumption of 23.4mpg! I must do the calculations from my fuel log and see what the real consumption is.

Hmm, thought so. Based on the pump and odometer readings, it calculates out to 21.85 mpg - almost 7% out. I guess that I could have a go at adjusting the DIS calibration using VAG-COM.

[peterb]

Yep - it's a bit disconcerting on the drive to the garage, isn't it?

[ChrisB]

250 miles on a tank! I thought I was always on the boost, but you must be hammering it all the time! [img]images/graemlins/smile.gif[/img]

I usually get around 280 to 320 out of a tank doing rural A-road driving 'enthusiastically'. Poor fuel consumption might be a symptom of a slipping lockup clutch - do you notice the revs climbing without a speed increase often?

The DIS seems to be hopelessly optimistic on a full tank and pessemistic on a nearly empty one - I often fiill up to be given a 400 mile range and still have a 200 mile range at half a tank only to find the last quarter of a tank drops from 100 mile range to 35 (usually where my 9 litres warning kicks in) in far less than 65 miles...

The low fuel in the morning thing had happened on all my Audis - I can put the RS 6 away with 60 miles on it after some spirited driving and the following morning it's only showing 10 or 15, although I've done over 30 in that condition and still only been able to squeeze 76 litres in.

[Riz_RS4]

250 miles on a tank! I thought I was always on the boost, but you must be hammering it all the time!

thats what i get out of my S3 IIRC. [img]images/graemlins/thumb.gif[/img]

[Dippy]

I too think the miles remaining is based on a rolling average of the mpg for the last x miles driving.

It is also clearly pessimistic: On many times I have filled up at 0 miles remaining (or even -5 to -10 if that could have been displayed) and always have 3-4 litres left in the tank.

N.B. IIRC the S4/RS4 tank is 60 litres and not 62.

[boff]

If you really really care for the RS6 on Motorways the tank is good for 460miles and the DIS reports this well, infact the further i drove the more it told me I had left!!

Only managed this once though, usually between 200 and 350 on a tank (London Stop-Start doesn't help) The DIS definately works to your style of driving, I too can have 60 miles left........but then I get a wicked grin and within 5 miles can be showing only 15 miles left.

[rwoodward]

I think the DIS displays fuel remaining based on your consumption over the last 30 miles - so if you hammer the throttle it'll drop down fast, or likewise take things easy and it can go back up .. (im sure i saw mine go up.. once..)

The calculations on this are separate from the average consumption figure which can be reset when required..

Ross

[Nige_RS4]

250 miles on a tank! I thought I was always on the boost, but you must be hammering it all the time!

I usually get around 280 to 320 out of a tank doing rural A-road driving 'enthusiastically'. Poor fuel consumption might be a symptom of a slipping lockup clutch - do you notice the revs climbing without a speed increase often?

I too get 250 miles out of a tankful, based on fast A road and motorway blasts (my DIS shows 39mph average which I thought was far too low, but based on others, it's quite high) - is you car chipped ?

I've noticed that when my car is cold the range drops dramatically from the previous night, but as it warms up, the range increases, which kind of suggests that the DIS takes into account the extra fuel used during warm-up ??