Fuel computer confusion by raistlin (Page 1 of 2)


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raistlin
Usually, VeeKay's fuel computer shows between 480 and 490 miles range when the tank has just been filled.

However, filled her up yesterday and it shows merely 348 miles as the range.

Not that I rely on it of course but it's annoying when something isn't right.

Does anybody have any ideas please?
Paul

Cogito ergo sum... maybe?

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Posted 05 Feb 2013, 18:48 #1 

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Jürgen
Have you been in stop and go traffic just before filling up Paul? Then the computer is calculating with less MPG. Or maybe you couldn't fill the tank completely, because the diesel had build up more foam than usual?
Jürgen

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Posted 05 Feb 2013, 19:14 #2 

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James.uk
The cold weather may also be a factor innit.. :)

Posted 05 Feb 2013, 19:17 #3 

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raistlin
Thanks chaps :)

The tank was full to the brim Jürgen but I know what you mean :) Hadn't been in traffic either :(

Didn't seem to make any difference over the cold spells previously James.

I wonder if it has anything to do with the re-map and disabling the Synergy?
Paul

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Posted 05 Feb 2013, 20:11 #4 

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Jürgen
raistlin wrote:I wonder if it has anything to do with the re-map and disabling the Synergy?

I think this is plausible, Paul. I guess the computer will need a few runs to recalibrate now.
Jürgen

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Posted 05 Feb 2013, 21:47 #5 

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Bermudan 75
Is it one of those things that sorts itself out with a 30 minute disconnection of the battery I wonder ?
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Posted 08 Feb 2013, 23:59 #6 

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Colvert
It's because the computer continuously updates the distance you can travel with the fuel in the tank against your current driving style.

Drive carefully ( ie at 40mph. ) and it'll tell you that you can drive zillions of miles with whats it the tank. Lol.



Colvert.

Posted 12 Feb 2013, 20:09 #7 

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Colvert
Rover418275 wrote:Is it one of those things that sorts itself out with a 30 minute disconnection of the battery I wonder ?


Nowt wrong with it. That's how it's designed to work. Leave your battery alone. Lol.

Posted 12 Feb 2013, 20:11 #8 

Last edited by Colvert on 12 Feb 2013, 20:25, edited 1 time in total.

User avatar
raistlin
Jürgen wrote:
raistlin wrote:I wonder if it has anything to do with the re-map and disabling the Synergy?

I think this is plausible, Paul. I guess the computer will need a few runs to recalibrate now.


You're right of course Jürgen :) It is gradually settling down again.

All I need to do now is re-calibrate the fuel consumption algorithm to reflect the car's true brim to brim values.
Paul

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Posted 12 Feb 2013, 20:14 #9 

Last edited by raistlin on 12 Feb 2013, 20:35, edited 1 time in total.

User avatar
raistlin
Rover418275 wrote:Is it one of those things that sorts itself out with a 30 minute disconnection of the battery I wonder ?


I did try that Mike, or rather, we had the battery out for an hour while we located the ABS (Antilock Braking System) modulator, but to no avail. Thanks for the idea though :)
Paul

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Posted 12 Feb 2013, 20:15 #10 

Last edited by raistlin on 12 Feb 2013, 20:38, edited 1 time in total.

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Colvert
raistlin wrote:
Rover418275 wrote:Is it one of those things that sorts itself out with a 30 minute disconnection of the battery I wonder ?


I did try that Mike, but to no avail. Thanks for the idea though :)


Stop playing with it or you are going to break something that's not broken. :oops: :wales: :wales: :wales: :cheers:

Posted 12 Feb 2013, 20:29 #11 

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Duncan
Here's a maths question based on a trip computer.

If a man, starts a journey in the morning with the trip computer saying there is enough fuel in the tank to travel another 355 miles, and he then drives a further 50 miles. How many miles does the trip computer now tell him can be driven on the fuel remaining in the tank. Hint, the average consumption over the journey was 55MPG.
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Posted 12 Feb 2013, 20:48 #12 

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Trebor
304.7
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Posted 13 Feb 2013, 16:08 #13 

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Duncan
Trebor wrote:304.7

Close but no cigar. You see you were using mathematics, not random number generation like trip computers seem to use. The actual answer was 375 miles range at the end of the journey.

Madness.
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Posted 13 Feb 2013, 19:52 #14 

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raistlin
Don't see anything wrong in it myself Duncan :lol:
Paul

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Posted 13 Feb 2013, 20:01 #15 

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Bermudan 75
So it wasn't maths it was, 'pick a number, any number...' :lol:
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Posted 13 Feb 2013, 22:48 #16 

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Duncan
Now see, it's not that bad in the end. 300 miles after saying there was 355 miles in the tank, it says there's 50 left in the tank. So why did it get the maths so wrong in the first place?
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Posted 14 Feb 2013, 18:59 #17 

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Bernard
Maybe the fuel consumption was lower for the first 50 miles, in which case the computer would recalculate accordingly and up its prediction.
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Posted 14 Feb 2013, 19:35 #18 

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Colvert
Bernard wrote:Maybe the fuel consumption was lower for the first 50 miles, in which case the computer would recalculate accordingly and up its prediction.


Totally correct---Give that man a cigar. :iagree: :hail: :hail: :stirer:

Posted 14 Feb 2013, 21:02 #19 

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Duncan
It could have been, but the car had been doing the exact same run the day before, and the days after. Same time of day so same traffic, same roads, everything. It had done a different run one day earlier, but even then a not dissimilar kind of journey

Now on the 75, I can see what happens. My drive has a slight slope, and the fuel gauge averaging gets upset by parking back end downwards. I can park up with a 1/4 tank and restart in the morning and find only 1/8th. The fuel then gradually 'reappears' after a few minutes driving. But my other car doesn't show this gauge 'funny' and isn't consistent with the range increasing so much during a journey.
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Posted 14 Feb 2013, 21:15 #20 


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