Clubjazz - Honda Jazz & HR-V Forums

Honda Jazz Forums => Honda Jazz Mk4 2020 - => Topic started by: JJazz on April 27, 2022, 11:26:29 AM

Title: Fuel Gauge
Post by: JJazz on April 27, 2022, 11:26:29 AM
I just filled up with petrol and fuel gauge reads 468 on dashboard. I have seen this much higher, even 625 when I got the car I seem to remember?. From previous experience I have seen the gauge go up after a while. Am I going mad?.
Title: Re: Fuel Gauge
Post by: Kremmen on April 27, 2022, 11:47:37 AM
We've had similar reports.

Have you reset both trips at refuel ? If not then it 'could' be calculating based on your current MPG.

Edit: I see you are still showing an uninitialised trip B so that's probably the reason. It'll be based on that current 60mpg.
Title: Re: Fuel Gauge
Post by: JJazz on April 27, 2022, 11:51:06 AM
I will try that. Never usually reset trips as don’t go anywhere, ha ha. Obviously gauge on far right shows full tank.

This photo from early Feb shows 573 miles on gauge.
Title: Re: Fuel Gauge
Post by: ColinS on April 27, 2022, 12:02:59 PM
On my previous MKIII Jazz and on this HR-V it always reads 426 (I think it is) after filling and then adjusts after a few miles of diving.  It will then go up and down based on my current driving style.
Title: Re: Fuel Gauge
Post by: Kremmen on April 27, 2022, 12:07:34 PM
I've got trip A reset at refuel and trip B reset each ignition off.

Must check what mine starts off at next refill.
Title: Re: Fuel Gauge
Post by: Lord Voltermore on April 27, 2022, 12:24:48 PM

It estimates range  based on recent mpg history, and initially  assumes this mpg will continue.  .   This may have included periods when mpg is worse than usual   such as cold starts and high motorway speeds .

  After a while it gives a new range forecast based on your current mpg. It could go up  :D  but could go down if for instance you are now driving at higher motorway speeds.
Title: Re: Fuel Gauge
Post by: JJazz on April 27, 2022, 12:30:20 PM
Why can’t it just be what’s in the tank.

Just been into garage and reset trips to zero. I have set both now to fully refuelled after some messing about. Messed up my mpg now and fuel gauge number not went up. Will see if fuel gauge goes up over next few weeks which I expect.
Title: Re: Fuel Gauge
Post by: Kremmen on April 27, 2022, 01:28:22 PM
For my total car mpg I use Spritmonitor, which appears in the left column under my avatar.

This uses real world fuel inserted v miles covered. Saves using a spreadsheet if you're that way inclined.
Title: Re: Fuel Gauge
Post by: ColinB on April 27, 2022, 02:57:01 PM
I just filled up with petrol and fuel gauge reads 468 on dashboard. I have seen this much higher, even 625 when I got the car I seem to remember?. From previous experience I have seen the gauge go up after a while. Am I going mad?.

You're not looking at a fuel gauge, you're looking at a range prediction. As others have said that will vary as you drive. Somewhere there'll be a tank level indicator (usually a series of bars that reduce as you use fuel).
Title: Re: Fuel Gauge
Post by: shufty on April 27, 2022, 03:02:18 PM
...I've experienced the fuel gauge go down a notch and then a few miles later go back up one. From 9 to 8 then back to 9. It could have been just the balance/level of the car although it did take a few mins and a few miles to do this so not so sure  :-\
Title: Re: Fuel Gauge
Post by: ColinS on April 27, 2022, 03:18:00 PM
It estimates range based on recent mpg history ...

Where did you find this information?  It cannot be true as my MKIII always showed 426 miles no matter how I had previously been driving.  I am thinking that it must be a factory pre-set value, maybe based on the minimum you should expect and then correcting to a more realistic figure over the next few miles.
Title: Re: Fuel Gauge
Post by: Jazzik on April 27, 2022, 03:19:19 PM
Am I going mad?.

You're not looking at a fuel gauge, you're looking at a range prediction. As others have said that will vary as you drive. Somewhere there'll be a tank level indicator (usually a series of bars that reduce as you use fuel).

You are not going mad, but you are confusing the fuel gauge with predicted range. At the very right you see your fuel gauge, showing 10 bars.
Next to it (right side) it shows a fuel pump:
(https://emojipedia-us.s3.dualstack.us-west-1.amazonaws.com/thumbs/120/samsung/320/fuel-pump_26fd.png)
(https://clubjazz.org/forum/index.php?action=dlattach;topic=14605.0;attach=8845;image)
Title: Re: Fuel Gauge
Post by: JJazz on April 27, 2022, 04:54:33 PM
Thanks everyone. I searched online. Here is answer

Range

Shows the estimated distance you can travel on the remaining fuel. This distance is estimated from the fuel economy of your previous trips.
Title: Re: Fuel Gauge
Post by: Kremmen on April 27, 2022, 04:59:22 PM
Nice find  :)
Title: Re: Fuel Gauge
Post by: ColinS on April 27, 2022, 05:01:10 PM
Thanks everyone. I searched online. Here is answer

Range

Shows the estimated distance you can travel on the remaining fuel. This distance is estimated from the fuel economy of your previous trips.

That is true but it doesn't explain why it is a fixed figure immediately after filling up.  I don't suppose it really matters a hoot, it's just that I have now got interested.
Title: Re: Fuel Gauge
Post by: Lord Voltermore on April 27, 2022, 05:51:52 PM


That is true but it doesn't explain why it is a fixed figure immediately after filling up.  I don't suppose it really matters a hoot, it's just that I have now got interested.

Why not?   Once the system knows you now have say 40 litres in the tank  the mk 4  computer is programmed to instantly work out that if your previous  trip was 50 mpg the range  will be  about  439 miles,(assuming you continue to drive in a similar way )or if it  were 75 mpg it would be   659 miles.    The Mk3 may be programmed to initially  always  show 426 miles   ,probably a typical average for the car.    But  either  method will be inaccurate because future mpg is not yet known.   You are unlikely continue driving at  exactly 50 mpg, 75 mpg or the 48 mpg needed for 426 mile range.   
Title: Re: Fuel Gauge
Post by: ColinS on April 27, 2022, 07:04:05 PM
The Mk3 may be programmed to initially  always  show 426 miles, probably a typical average for the car.

That was my guess.  You clearly don't know either.  The MK3 obviously operates differently than the MK4.  Anyway it is irrelevant.
Title: Re: Fuel Gauge
Post by: Kremmen on April 28, 2022, 06:07:08 AM
The fuel range display using previous saved average mpg makes sense to me. Makes the figure more realistic.

The maths:

Our 40 litre tank is about 8.8 gallons.

600 mile range on 8.8 gallons is about 68mpg

My initial few tank range displays were over 600 miles so I suspect it was based on 70mpg until it got data.

Title: Re: Fuel Gauge
Post by: Lord Voltermore on April 28, 2022, 09:41:45 AM
The Mk3 may be programmed to initially  always  show 426 miles, probably a typical average for the car.

That was my guess.  You clearly don't know either.  The MK3 obviously operates differently than the MK4.  Anyway it is irrelevant.
No I dont know  for sure, and I may be wrong.  But on this issue its a logical enough explanation  for me.  Sometimes  ignorance is bliss   :-* 

 There  again Mr Spock was only the first officer.  Captain Kirk was a human.  ;D . I suppose if every one  though  like me we would still be hunter gatherers , but I like to think I am ingenious enough  we would have fast loading multi shot  crossbows capable of taking down a mammoth and live in  comfortable caves.    8)

Title: Re: Fuel Gauge
Post by: nowster on April 30, 2022, 07:17:07 PM
On the Mk4 if you top up when the fuel gauge on the right is showing full or just one bar off full, the range estimation doesn't usually update from what it was before you filled up.
Title: Re: Fuel Gauge
Post by: JJazz on April 30, 2022, 07:51:30 PM
When I picked up my car in September it had 625 on dash. I remember as I asked about it and salesman said number of miles for full tank. I said that’s about 70 mpg. Obviously Honda set it up like that. I will never see that again doing short journeys.
Did calculation - see photo
Title: Re: Fuel Gauge
Post by: Kremmen on May 01, 2022, 04:22:31 AM
I wonder if the tank range uses just the last MPG or all 3 in the trip computer.
Title: Re: Fuel Gauge
Post by: sportse on May 01, 2022, 07:46:15 AM
When I picked up my car with 8 miles on it, the range was 650 miles.

Never repeated, until the car had its battery disconnected for an hour, when it went back to 600+ again.

Over winter I had a range right around 400 miles for months, but with the warmer weather its been showing 480 over the last few fill ups.
Title: Re: Fuel Gauge
Post by: Bristol_Crosstar on May 01, 2022, 08:54:22 AM
My Crosstar always shows above 500 after filling up, usually 520-540. In practice I've never done more than 450 miles before re-filling (I think there was one block left at that point) so have never put it to the test.
Title: Re: Fuel Gauge
Post by: John Ratsey on May 02, 2022, 09:40:02 PM
The miles remaining clearly uses recent (I'm not sure how recent - 10 miles??) mpg as that is what is assumed will apply in the future. If you travel down the motorway at 75 mph (ie no better than 50mpg) and stop to refuel then the forecast range on the refill will be nearer 400 miles (40 litres = 8.8 gallons at 50mpg = 440 miles). If you've recently been travelling more slowly and getting 70mpg then the forecast range on refill is over 600 miles (8.8 x 70 = 616 miles). During a journey with different driving conditions you can watch this calculation process. Do some slower driving and the range looks good, then hit the motorway and the miles remaining will go down faster than the miles travelling. Then get back to slower roads and the forecast miles remaining might actually increase although you are using up the miles.
Title: Re: Fuel Gauge
Post by: Kremmen on May 03, 2022, 05:28:49 AM
On a similar note, last year I hired a Transit. They noted that the tank range was about 400 miles, I forget the exact figure.

They said that I need to make sure the tank range was no lower when I dropped it off. I only did a 60 mile return journey but the tank range was about 450, and the fuel gauge was still hovering around 3/4 so I didn't put any diesel in  :)
Title: Re: Fuel Gauge
Post by: guest9814 on May 06, 2022, 02:59:11 PM
On the Mk4 if you top up when the fuel gauge on the right is showing full or just one bar off full, the range estimation doesn't usually update from what it was before you filled up.
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 it’s recalculate after passing 92% ?
That because fuel capacity of tank that bigger then 92% not measured in MK4. If tank filled 93-110% it’s full for fuel gauge.
Last fill up I seen 1070km remaining , but when I burned 10% of “full“ fuel tank and drive 144km computer recalculate remaining km from 860 to 970km.
Title: Re: Fuel Gauge
Post by: Wonder on May 06, 2022, 03:16:48 PM
Hello,
in Italy the car has a 40 liter tank,
and I noticed that the LEDs that indicate the fuel level are 10,
I would think that each LED corresponds to 4 liters (40 liters / 10 LEDs) is an approximation of this type possible or is it too wrong?
Title: Re: Fuel Gauge
Post by: JJazz on May 06, 2022, 09:27:08 PM
An update on my 467 range after resetting trip when I topped up tank.

Looking at my range it’s 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.
Title: Re: Fuel Gauge
Post by: Marmoset on May 07, 2022, 11:39:05 AM
An update on my 467 range after resetting trip when I topped up tank.

Looking at my range it’s 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. 
Title: Re: Fuel Gauge
Post by: Lord Voltermore 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 it’s 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. 

Title: Re: Fuel Gauge
Post by: ColinS 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 it’s recalculate after passing 92% ?
That because fuel capacity of tank that bigger then 92% not measured in MK4. If tank filled 93-110% it’s 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.
Title: Re: Fuel Gauge
Post by: guest9814 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 it’s recalculate after passing 92% ?
That because fuel capacity of tank that bigger then 92% not measured in MK4. If tank filled 93-110% it’s 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.
Title: Re: Fuel Gauge
Post by: Bazzzer 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.
Title: Re: Fuel Gauge
Post by: Jazzik 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? (https://www.cheesebuerger.de/images/smilie/nahrung/f015.gif)
Title: Re: Fuel Gauge
Post by: ColinB 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".
Title: Re: Fuel Gauge
Post by: Lord Voltermore 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.   
Title: Re: Fuel Gauge
Post by: aphybrid on May 11, 2022, 12:22:36 PM
Crosstar owners have less meaning in life then at 40(litres)
Title: Re: Fuel Gauge
Post by: Kremmen 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.
Title: Re: Fuel Gauge
Post by: MRCLICKCLICK 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.
Title: Re: Fuel Gauge
Post by: JJazz 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

Title: Re: Fuel Gauge
Post by: guest9814 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.