Author Topic: Fuel Gauge  (Read 1875 times)

Lord Voltermore

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Re: Fuel Gauge
« Reply #30 on: May 07, 2022, 04:16:07 PM »
An update on my 467 range after resetting trip when I topped up tank.

Looking at my range itís now 501 plus I have completed 91.3 miles so looking like 592.3 for my tank of petrol. I still got 10 bars on right. Probably be much changed in a day or two.
And looking at things the other way round, with the metre set to return to zero after a fuel refill, I had 357.7 miles done and 264 as range (so 621.7 miles on that rather economical tank) on the way to the petrol station but 580 miles after filling up. So, clearly, the range estimate is not based purely on recent driving. I'm now wondering whether it's taking the life history of the car's consumption figures.
The computer probably initially  calculates based on the nominal tank capacity of 40 litres.  The float gauge shows its full ,so its assumed to be  40 litres.

  But in reality you can often get more fuel  in than that.  You may have  2 litres  sitting in  the filler neck and pipes . You will get  an extra 30 -50 miles of range using this   before the level in the tank itself  even begins to drop below full and the difference can be detected.
For example  when the gauge shows the tank as half full its fairly accurate to say there are 20 litres remaining.       But you may have already used 22 litres of fuel before the tank reaches this level.   
The extra 2 litres will not have been detected  or used in early range calculations.

The range may be longer than estimate  , but you've not really gained.  Its the result of using  42 litres of fuel, not 40.   You still have to pay for the extra  >:(

When brimmed my old Yaris would do about 100 miles before it dropped its first fuel  gauge bar.  But thereafter it was one every 50 miles or so. 

Sorry if its too long winded. I failed my brevity exam at school. Ran out of paper.

ColinS

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Re: Fuel Gauge
« Reply #31 on: May 07, 2022, 04:27:38 PM »
MK4 computer recalculate distance to empty always after fuel pass 92% of fuel tank capacity, when you topping up tank to full from empty computer shows what you can get from full tank by judging your previous tank mpg, but why itís recalculate after passing 92% ?
That because fuel capacity of tank that bigger then 92% not measured in MK4. If tank filled 93-110% itís full for fuel gauge.
I like this theory.  But is it based on known fact?  If so I would be interested to read the source.

Roman

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Re: Fuel Gauge
« Reply #32 on: May 07, 2022, 07:33:32 PM »
MK4 computer recalculate distance to empty always after fuel pass 92% of fuel tank capacity, when you topping up tank to full from empty computer shows what you can get from full tank by judging your previous tank mpg, but why itís recalculate after passing 92% ?
That because fuel capacity of tank that bigger then 92% not measured in MK4. If tank filled 93-110% itís full for fuel gauge.
I like this theory.  But is it based on known fact?  If so I would be interested to read the source.
I reading car sensors data using OBD2 port and application - Car scanner
Percentage of fuel tank filled with fuel starting to fluctuate and change only when amount of fuel in tank less then 92% (i filling tank to full but sensor shows only up to 92%).
When data from fuel level sensor star to fluctuate around 91-92% computer starting recalculate remaining km to empty and now computer uses current mpg.
I can see often during drive how computer starting to add km to empty, and that happens when computer starting reading fluctuations of fuel level sensor.

Bazzzer

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Re: Fuel Gauge
« Reply #33 on: May 09, 2022, 03:07:56 PM »
In my Mk.3 today, range was showing 241m which dropped by 1m at a time to 235. I was a bit surprised to see it falling as the road was slightly downhill

After following a tractor for a couple of miles, it suddenly showed within 4-5 seconds 235 ... 240 ... 245 ... 250 ...255

When I looked again 2-3 minutes later it was showing 306m and another few minutes later, 287miles.

Jazzik

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Re: Fuel Gauge
« Reply #34 on: May 09, 2022, 03:34:47 PM »
...it suddenly showed within 4-5 seconds 235 ... 240 ... 245 ... 250 ...255

When I looked again 2-3 minutes later it was showing 306m and another few minutes later, 287miles.

Are you absolutely sure you have petrol in your tank and no whiskey?
Stay on the right side of the road (I mean here, mainland Europe, the >>> RIGHT side).

ColinB

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Re: Fuel Gauge
« Reply #35 on: May 09, 2022, 05:48:26 PM »
In my Mk.3 today, range was showing 241m which dropped by 1m at a time to 235. I was a bit surprised to see it falling as the road was slightly downhill

After following a tractor for a couple of miles, it suddenly showed within 4-5 seconds 235 ... 240 ... 245 ... 250 ...255

When I looked again 2-3 minutes later it was showing 306m and another few minutes later, 287miles.

I can confirm that behaviour. I have watched the range estimate bounce up and down by +/- 50 miles or more, completely unrelated to the actual distance being covered. That's why I'm astonished at folks using it to judge their refuelling. Maybe it's better in the Mk4, but in the Mk3 it's very "ballpark".

Lord Voltermore

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Re: Fuel Gauge
« Reply #36 on: May 11, 2022, 12:00:41 PM »
For reasons too long to explain I have just brimmed my tank, very soon after it dropped to 7 bars.  In theory 10 bars on a 40 litre tank is 4 litres per bar. 3 bars should have taken 12 litres.  It took 14.5 litres, suggesting there is indeed  some extra in the filler neck.
Range initially showed 594 miles equating to   67.5 mpg for 40 litres.  My average over the previous 1300 miles had been 69.1 mpg  ,and my most recent  long trip (100 miles or so) was 74.9 mpg.   
For the first 0.2 miles in ev mode I averaged 194 mpg  -( if only  ;D )   But then the engine started,and a bit of a hill , It instantly dropped to 142 mpg, then a few seconds later into the 60's and a few seconds after that into the 50's. 
During these rapid changes  the range estimate dropped to 562,  then soon after  to 560, then 558.    So it was still expecting me to average in the mid 60's even though at that moment I was getting low 50's mpg and worse.
   
Lifes too short to worry about how it estimates and calculates. Or to rely on it  .   The proof of the pudding is how much fuel you actually need to put in the tank, and whether you managed to reach the filling station. :P

As fans of "The hitchhikers guide to the galaxy " will know it took a computer 7.5 million years to work out that the answer to the ultimate  meaning of life, the galaxy and everything  is 42.      Its right! 42 litres.  :-*

My 74.9mpg was on a trip to snowdonia , north wales.    When descending from an elevation of 700 ft or so  (a whole   
213 metres  - and they they call them mountains ! )  down to sea level  I got well into the 80's mpg.  Climbing again it was low 50's.  Yet crucially the gradients were so gradual  I didnt really notice  the difference -but the fuel consumption certainly did.   
Sorry if its too long winded. I failed my brevity exam at school. Ran out of paper.

aphybrid

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Re: Fuel Gauge
« Reply #37 on: May 11, 2022, 12:22:36 PM »
Crosstar owners have less meaning in life then at 40(litres)

Kremmen

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Re: Fuel Gauge
« Reply #38 on: May 11, 2022, 12:56:05 PM »
Doesn't bother me either, it can report what it wants.

As soon as the bars drop below half I fill up.

Just for my info though I put my fill ups into Spritmonitor as that method shows the true mpg.
Let's be careful out there !

MRCLICKCLICK

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Re: Fuel Gauge
« Reply #39 on: May 12, 2022, 09:20:58 AM »
Remember - that fuel has weight - so the more you use - the better the consumption ( when the ice is in operation), or put another way - take the tank down to almost empty, and NEVER fill right up - ( unless on a long journey) - if it town quarter full is more economical.

JJazz

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Re: Fuel Gauge
« Reply #40 on: May 14, 2022, 10:47:07 AM »
My latest this morning. 9 bars and mileage plus range works out at 582.3 miles. Still on Econ

« Last Edit: May 14, 2022, 10:50:44 AM by JJazz »

Roman

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Re: Fuel Gauge
« Reply #41 on: May 14, 2022, 01:01:18 PM »
Remember - that fuel has weight - so the more you use - the better the consumption ( when the ice is in operation), or put another way - take the tank down to almost empty, and NEVER fill right up - ( unless on a long journey) - if it town quarter full is more economical.
Well i some time ago checked that because i not have money to fill full tank and already reached reserve of fuel in tank 5.7l, i filled 5 liters and reset trip A and B fuel econmy, i got same figures that i get with full tank, but that may be because of my weight  :D.

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