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Author Topic: Incorrect fuel reading  (Read 9658 times)
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Matheus Britto
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« on: June 18, 2014, 12:47:57 pm »

Hi guys.

I using the last version of DS (on iPad Mini Retina Display) about a week and notice that the fuel reading is not right.
Yesterday I fill up the tank and the DS is showing about 41.6L (83.1%), instead of 50L (100%).
Anyone have any idea about what's going wrong or can help me?

My configs (using the owners manual and some infos from internet):
Model: VW Fox G2 2014 5P (Brazilian Model)
Engine Displacement: 999cc (1.0 Flex)
Fuel Type: Gasoline
Fuel Tank Capacity: 50L
Tire Size Specification: 195/55/R15
Final Drive Ratios: Axle: 4,929; 1st Gear: 4,267; 2nd Gear: 2,301; 3rd Gear: 1,433; 4th Gear: 0,975; 5th Gear: 0,776
Curb Weight: 1009kg
Additional Weight: 110kg
Drag Coefficients: 0,353
Frontal Area: 2,17 m*m
Maximum Engine Speed: 8000 rpm
Minimum Engine Speed: 1000 rpm
Shift Point: 5000 rpm

Thanks for any help.
« Last Edit: June 18, 2014, 02:07:41 pm by Matheus Britto » Logged
Andy@PPE
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« Reply #1 on: June 18, 2014, 02:29:24 pm »

Our fuel feature is currently being adjusted to be more user friendly, keep in mind that in order to get accurate readings you will need to be connected to the vehicle 100% of the time that vehicle is in operation. Also make sure all the settings for your vehicle are entered and correct in your vehicle manager page. You can reset the fuel data by double tapping the steering wheel icon in the dashboard view.
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Matheus Britto
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« Reply #2 on: June 18, 2014, 03:30:34 pm »

Andy,

I spend all day trying to understand all infos/configs that DS shows me and I found this:

Fuel Level Input: 83.1% (41.6L)
Alcohol Fuel Percentage: 24.3%

And searching on the internet, I found that brazilian gasoline has 18~25% of ethanol (E25).

Now, I have some more questions about the fuel calculation (because I still not understand how the DS get this information).
1. The fuel blend could give a wrong reading?
2. How the DS reads the fuel tank (by liters or by weight)? How can I get the right values?
3. My ECU could be sending the wrong values of tank capacity? How to correct this?

Thanks for any help.
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John@PPE
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« Reply #3 on: June 18, 2014, 03:59:57 pm »

The fuel level comes from the SAE.EFI PID that your ECU is sending. This should not matter which fuel you are using.

The number of gallons in your tank comes from the percentage that the SAE.EFI tells us, and the tank size you input in the vehicle manager.

If your tank is showing 83.1%, it could mean that the sensor is off or maybe your tank is not supposed to reach %100 full. I'm sure what exactly the sensor is measuring, and you will ruin your car if you try to top off your gas tank.
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Matheus Britto
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« Reply #4 on: June 19, 2014, 01:59:36 am »

Guys,

After a couple hours, making a lot of tests and trying to discover what my ECU is sending (or not) to DashCommand, I figure out that the SAE.EFI PID is not listed… even at "All PIDs". So, this PID we can select or the data is sending automatically to DashCommand?

Another thing. It is possible that my WiFi OBD2 is not working properly or my ECU is not sending the right data? I'm asking because even after drive for about 10Km the fuel level input still 83.1% (41.6L).

Thank for any help.

In time: I checked the gas station bill, just to confirm how many gas I put a few days ago, and for my surprise… 41.6L. And before I fill up, DashCommand is showing me that I have approximately 8.2L.
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John@PPE
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« Reply #5 on: June 19, 2014, 11:25:06 am »

Sorry. I had a typo. It is the SAE.FLI PID.
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Matheus Britto
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« Reply #6 on: June 20, 2014, 12:47:35 pm »

John,

Before you answer me, I figure out that the "SAE.EFI PID" could be a error typing to "SAE.FLI PID". Relax…
But about the other information I send in the earlier post?

Another thing. It is possible that my WiFi OBD2 is not working properly or my ECU is not sending the right data? I'm asking because even after drive for about 10Km the fuel level input still 83.1% (41.6L).
In time: I checked the gas station bill, just to confirm how many gas I put a few days ago, and for my surprise… 41.6L. And before I fill up, DashCommand is showing me that I have approximately 8.2L.

It's possible, for unknown reason, that the ECU send only the fuel that I filled up and not the fuel tank (it would be strange but would be possible)?
All fuel consumption metrics is working fine, including the l/100Km Avg. Consumption (7.5l/100Km)

Thank for any help.

Matheus.
« Last Edit: June 20, 2014, 12:53:28 pm by Matheus Britto » Logged
John@PPE
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« Reply #7 on: June 20, 2014, 12:57:25 pm »

I am not sure on this one. What value is your SAE.FLI PID giving you? Does it appear to be accurate? If that value is incorrect then the reading will reflect the incorrect value.
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Matheus Britto
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« Reply #8 on: June 22, 2014, 10:47:26 am »

John,

Sorry not answer your question quickly, but as sports photographer I'm very busy this days (working in FIFA's World Cup 2014).

I talked to the VW tech guys to know the possibility of the ECU is not reading the correct fuel level and sending this wrong information to DC. They were not happy to know I'm using a WiFi OBD2 transmitter and a unknown software (they don't know DC) to directly read my ECU infos (they think they are the only ones allowed to do that). Anyway…

But they said it is extremely rare the fuel sensor or the ECU not work properly and send a inaccurate info to the on-board computer (or to OBD2 port) and I asked (I almost have to begging) to do a field test with the VW software in a small street circuit (about 5km) to see what the program show about fuel level. All the way ,the program showed the same fuel level I saw on my on-board computer (so, the fuel sensor and my ECU are working properly).

They were very angry because I used a OBD2 split cable to make the test with the WiFi transmitter and the VW software at the same time. They said they don't know how the DC works and why is showing a different fuel level.

After the test we can get this fuel results:
- VW software: 75% ~ 37.5l
- On-board: 75% ~ 37.5l
- DashCommand: 66% ~ 33l (difference of 9% ~ 4.5l)

This difference is almost the same of my reserve fuel tank (about 5l) and I really don't know why the DC is not counting this fuel in my tank.

Oh, I almost forgot one thing that could make a big difference. I don't know if it's true but one tech guy told me that everytime I put some fuel in tank all infos about time to empty and distance to empty are deleted and recalculated, based on the total of fuel in the tank. It's possible that the ECU has only sent to DC the fuel that I put and not the full tank?

And if I not fill up the tank but put more 4.5l in fill up correction, do you think that can correct this?

Thanks for any help.
« Last Edit: June 22, 2014, 01:17:41 pm by Matheus Britto » Logged
John@PPE
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« Reply #9 on: June 22, 2014, 12:05:43 pm »

I need to know what value SAE.FLI is showing. Go into the Data Grid and add a PID. Add the SAE.FLI PID. The value should be the percentage of fuel remaining in your tank. So if you have a quarter tank left it should show 25%.

Look at that and let me know if that PID appears to be reading correctly.
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Matheus Britto
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« Reply #10 on: June 22, 2014, 01:22:22 pm »

John,

I updated the earlier post, the info is above (SAE.FLI - 66%).
This value is totally inaccurate.  Undecided
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John@PPE
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« Reply #11 on: June 22, 2014, 06:26:16 pm »

In that case, DashCommand will be unable to get a correct reading. The VW probably has a sensor that has a correct value, but DashCommand is unable to read that sensor. Instead we are getting our result from the OBD-II port and it appears that value is not correct for whatever reason.
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Matheus Britto
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« Reply #12 on: June 25, 2014, 05:24:57 pm »

John,

Thanks for all support and help you gave me and I understand that sometimes the way to solve some problems are not in our hands.

If you allow me to suggest, on next update of DashCommand, I think that this options will be very welcome to all users.

1. In Settings > Units > Fuel Economy/Consumption option, could you put the option to choose km/l to make life easier (make this kind of math, all the time, is very annoying). So the user will have MPG, km/l and l/100km and could choose what is better for him (in my case, km/l). I saw that in another app (OBD Fusion) and like to have it on DashCommand.

2. In Vehicle > Advanced Settings, below the Fuel Tank Capacity (or inside this option), you can put a option to user fix the difference (in %) of the SAE.FLI wrong reading, and the app will take the SAE.FLI + the fuel correction as the total fuel in tank. If you let this option blank, the app take only SAE.FLI as the total fuel (as now).

Ex:
Fuel Tank Capacity: 50 l
SAE.FLI reading: 83.1% (~41.6 l)
User Correction: 16.9% (~8.4 l)
App Fuel Tank: 100% (50 l)

This way, even if the SAE.FLI gives the wrong value you can fix it and get the right value for the fuel tank, DTE and TTE (and all other metrics that use this info).

3. Log: Will be cool if we can start and stop the log data automatically. You just select the way the log will start (GPS or frame PIDs) and the app do the rest. I know there is another app (OBD Fusion) that work like this and it's very cool to use.

I think this can be done simply and easily and be ready for the next update.

Thanks again.
« Last Edit: June 25, 2014, 10:45:50 pm by Matheus Britto » Logged
John@PPE
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« Reply #13 on: June 25, 2014, 08:57:41 pm »

You said the SAE.FLI was 9% off. Is it still 9% off even as you drive the car, and the fuel is used up?
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Matheus Britto
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« Reply #14 on: June 25, 2014, 09:56:52 pm »

John,

When I filled up the tank the difference was 16.9% (~41.6 l instead 50 l), but in 3/4 of the tank the difference was 9% (~33 l instead 37.5 l). I think that when I get 1/2 of the tank, this difference can reach 4% or less (and I believe below this point there will be no difference). But I still believe that will be a good idea put a option to manually correct this.

I really don't know what's going on, but what I know is that the SAE.FLI is not getting the right value from the fuel tank… and there is nothing wrong with the sensor nor the ECU.

If you have any clue on what's going on, tell me, because I'm going crazy with this SAE.FLI wrong reading (and I believe it can mess with all other metrics results).

Thanks for your help.
« Last Edit: June 26, 2014, 06:24:08 pm by Matheus Britto » Logged
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