discrepancy between l/100km and l/h values

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discrepancy between l/100km and l/h values

sascha » 17 фев 2013, 23:31

Hi,

From time to time I observe strange combinations (in my setup at one screen) between the liters/100km and liters per hour dispite all other sensors seem to deliver plausible signals - e.g. l/h shows 5,0 and l/100km is 7,0 while running (almost) constantly with 50km/h (and proper updating speed value). The discrepancies can go in both directions - and stay persitantly for 10 or more seconds - sometimes even drifting further in the wrong direction - hence it seems to be really a wrong signal and not an integration constant/ damping (but which signal :roll: - it only needs the speed value to get from liters per hour to l/100km) I am pretty sure that this makes the consumption average faulty
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Re: discrepancy between l/100km and l/h values

cail » 18 фев 2013, 07:26

sacha,

L/h and l/100km are two different physical values - they do not need to be in sync at all.

L/h is a base value, showing "instant", per second, fuel consumption (converted to hours). It is directly connected to your throttle pedal.

l/100km is in contrast an integrated, average value, collected from overall trip (it uses l/h as an integration value).

This means, l/100km can't change instantly, as soon as you pressed your pedal.

There exist of course short term and instant fuel economy, which uses smaller integration intervals (5sec and 60 sec.) These two have more visible impact on your throttle/slowdown. Keep accelerating for 5 seconds and you'll see instant FE will raize significantly.
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Re: discrepancy between l/100km and l/h values

sascha » 18 фев 2013, 23:56

Ok, sorry - of course I mean the instantaneous fuel consumption l/100km - it's just the instantaneous velocity that makes the l/h to l/100km - and even if there is a limited 5second integration time for the l/100km - surely a bit higher than that what you have programmed to obtain the l/h (by integrating time variant rpm, manifold pressure, lambda and fixed values for displacement, volumetric efficiency and stoich ratio) - but it should be straigth forward that means that if l/h are decreasing while speed is constant the l/100km value should decrease/converge to a plausible value - not, as I have observed - drift even further to much too high (or in another case much to low) values. You know what I mean - it seems as one of the time variant values seems to be frozen at a wrong level - but there is only the speed that is missing in the equation which just seems to work fine all time.
Sometimes I have the feeling that it is just my mobile phone that has too low CPU performance - is there a way to find that out or somehow log the performance of hobdrive?
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Re: discrepancy between l/100km and l/h values

cail » 19 фев 2013, 13:15

You may checkout sensor update timing (tap status circle in left bottom corner). If it 300-400ms or faster - then everything is ok.

We are in abit vague ground here, because I don't see any real data to view on.
If you wish, you may enable Instant FE and L/H values logging, then we'll buildup the charts and visually findout if there are some "problematic" points.

Create file "user.track" in hobdrive's folder (/sdcard/hobdrive on android)
Код: Выделить всё
<?xml version="1.0" encoding='utf-8'?>
<sensor-track id="default" name="Basic sensor tracking configuration">
  <track sensor="FuelEconomy_instant"/>
  <track sensor="FuelEconomy_short"/>
  <track sensor="LitersPerHour" period='0'/>
</sensor-track>


After some rides, you'll get data logs in "track" subfolder. Put it here and we'll look at it.
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Re: discrepancy between l/100km and l/h values

sascha » 19 фев 2013, 20:21

Hi,

of course you are perfectly right - i will get some data logged - but again, I will need the speed values as well so I have added it to the sensors list in the exampel you have given.

Regards,
Sascha
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Re: discrepancy between l/100km and l/h values

sascha » 20 фев 2013, 23:15

Hi,

So after two rides I just checked and there is no tack data in the /track folder - at least nothing - don't know if these files have been created by former runs from me...
However, could it be the problem that two files: default.track (where everthing is commented out - like a tutorial) and the just yesterday created user.track exist? I found something in the forum saying that it ca be called either way - but so if have just renamed the default.track - I will see tomorrow - sound that promising to you?

Best regards,
Sascha
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Re: discrepancy between l/100km and l/h values

cail » 21 фев 2013, 05:45

There is some data in track folder even in the default configuration. Are you sure it is empty and you don't see any files at all?

Renaming should work, lets see. If nothing changes, put here a log.txt file from hobdrive's folder.
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Re: discrepancy between l/100km and l/h values

sascha » 21 фев 2013, 21:31

I wanted to write: atl least nothing new - so there are two sets of track files from last year.
With the user.track file it did not work - now I renamed it to default.track and will try again tomorrow.
But the content you posted earlier in the thread is ok? ;)
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Re: discrepancy between l/100km and l/h values

cail » 22 фев 2013, 05:10

Yes, the file's content is ok.

What do you mean with "last year"? there should be some fresh data.

With this updated content you'll see new files in there, like track0.FuelEconomy_instant
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Re: discrepancy between l/100km and l/h values

sascha » 22 фев 2013, 09:06

I mean the files creation date. They are old and nothing that I have intentionally created. Looks like files that are part of te installation respectively an example.

BUT!_ I have just checked again - I was looking in the wrong directory all time long - it was on the external memory of the phone, which I am not longer using since - yes, one year. :roll:
So in the actual hobdrive folder there are recent tracks - but of course not for the intendet sensors because there I have never updated the user.track file...embarrassing 8-)
I will come back ...
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Re: discrepancy between l/100km and l/h values

sascha » 26 фев 2013, 22:12

Hi Cail,

Now I got some track data! But I have some new questions.:
1. The tracks are overwritten every day - despite these with *common* in the name - they are appended.Correct? What does *filtered* in the track name mean - the others I think I can interpret but:
2. where are all the other sensors defined?
3. The sensors I added/ created in the user.track are there as well - but the sensor speed has a much coarser time interval - I can remember that you wrote in another thread that a synchronous write out of the sensors is not possible - but there are all - despite the speed sensor (which I need)- in roughtly the same time steps written out - good enough to do some line based maths in excel. Is that from importance that the speed sensor log data includes the word *obd* is that coming from another source?
4. How can I set up that every day a new set of tracks (for the non *common* sensors) is created - perfect would be the date in the folder name?
Thanks in advance!
Best regards,
Sascha
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Re: discrepancy between l/100km and l/h values

cail » 04 мар 2013, 08:38

Sascha,

1. Yes, the data is always appended to the end.
2. You may read doc/hobdSensors.html file to search for more sensor names, or just openup "All sensors" Screen

3. hobdrive may change sensor read periods on its own needs - thats why some of them may go faster than others.
We have a tools to improve excel parsing, take them on this page:
viewtopic.php?f=12&t=98
(its in russian, but you just download the files). It allows you to join sensor times and make good charts out of logs.

4. thats not possible for now unfortuately. We'll consider improving this functionality in future.
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