OBDMPG - MPG OBDII Plugin for RR 6-12-09

**tom_rosenback** · 11-14-2008, 01:06 AM

Hi, Super project, just the project I have been looking for!! THX!!

I looked into your code and noticed the MPG calculation. I have read on some forum, might even be here, that taking LTFT into the calculation will give a more exact MPG calculation since the stoichometric constant is not all the time exactly 14.7 So for metric calculation the formula would be MPG = MAF / 14.7 * (1 + (LTFT / 100)) * 3600 / 786 / SPEED * 100, should be at least, setting LTFT to 0 should give the same result as your formula.

Also the MPG should not be calculated if overrunning the car.

Thanks again for your project, if you need any help, just tell me.

**mezz64** · 11-14-2008, 01:13 AM

Thanks for the input Tom, however I've already tried the LTFT implementation and noticed no significant difference in the calculations.

I believe the addition of LTFT to the equation was debunked as well. I've found the data in this thread to be quite accurate, especially the posts by Mr. Lightner.
http://www.mp3car.com/vbulletin/engi...-maf-obd2.html

Can you be a little more specific about what you mean by "overrunning" the car? I am still looking for ways to make things more accurate so all feedback is welcome.

**tom_rosenback** · 11-14-2008, 02:10 AM

If you have a car with injection and you are running down the road and then take your foot off the gaspedal the consumption will be 0. This is overrunning, in other words engine breaking. I noticed when doing some logging with VAG-Com that when overrunning MAF gives values greater than 0 which gives a consumption result greater than 0.

**mezz64** · 11-15-2008, 11:57 PM

Update has been posted!

There are some significant changes in this release. Make sure to take a look at the skin_commands.txt file to note the command changes. I modified everything to be metric/english friendly, so for instance, "obd_insmpg" is now "obd_insfe".

Also metric/english is fully interchangeable. If you wish to use metric feel free to specify tank size in liters. All commands now report units as well so it should be easier to tell what the number means.

I've also rewritten the fuel usage calculations to utilize the MAF value better and done an overall code cleanup, calculations are computed more often (every 1/4 second) than before and the adjustment calculator has been modified to use the VE factor for non-MAF vehicles.

I've also been able to get a few basic flash gauges working. I did this as kind of a proof of concept. I'm not going to go any further with the design in Carwings as I've been meaning to make a skin of my own for some time and I feel my design efforts would be better focused there. A screenshot is below. This sample skin shown and the .swf files are included in the latest release zip. You can access the skin from the carwings menu by using my included menu2.skin file and clicking the blank slot below "Obd" for the time being.

One other thing to mention is due to the increase in the calculation interval if you run the plugin for more than 3hrs or so you will get an overflow error. I've got a way around this and am in the middle of implementing it. I'll post up an update once I get it fixed.

**tom_rosenback** · 11-17-2008, 05:13 AM

Hi, I just looked into your source code and saw that the metric calculation of fuel effiency is in km/liter while FE in metric should be given as liters / 100km. Did I miss something in your code or is it this way?

Is the source code link updated in the same pace as the application link?

Btw had to order a chinese ELM327 device from ebay so that I can run your plugin...

Thx!!

**Sonicxtacy02** · 11-17-2008, 10:03 AM

this is coming along really nice. i cant wait to get the time to implement it into my car

**mezz64** · 11-17-2008, 11:58 AM

Originally Posted by tom_rosenback

Hi, I just looked into your source code and saw that the metric calculation of fuel effiency is in km/liter while FE in metric should be given as liters / 100km. Did I miss something in your code or is it this way?

Is the source code link updated in the same pace as the application link?

Btw had to order a chinese ELM327 device from ebay so that I can run your plugin...

Thx!!

It is indeed in km/liter. I kind of just assumed that since its miles/gallon, the metric equivalent would be km/liter. I can change it to liters/100km no problem just wasn't aware of the difference.

**NiMar** · 11-17-2008, 02:19 PM

Originally Posted by mezz64

It is indeed in km/liter. I kind of just assumed that since its miles/gallon, the metric equivalent would be km/liter. I can change it to liters/100km no problem just wasn't aware of the difference.

Yes, metric equivalent must be litres/100km.
Your last version work better and now i see calculations!!!!!

Now the result of short testing:
1. For Russian regional settings there must be ","as separator in ini. for example: LITERS=2,5
2. Connected indicator doesn't work for me

don't know why.
3. Arrows on flash gauges and digital value on them sometimes doesn't match. i.e. arrow show on 30, but numeric value is 5.
4. Sometimes Arrows on flash gauges start slowly to rising, but the value is not changed.
5. Several times Vehicle speed freezed on some value(i.e. 30) and doesn't change even when car is stopped. i reconnected ELM to car at it became working.

Suggestions:
1. Changeable flash gauges background color and digits color (ini-file)
2. Is there any way to speed up PID's receiving? sometimes the delay of receiving the values became 3-5 seconds.
3. Can you not to add "km" or "l" after the values? I want to write it by myself in russian in Roadrunner skin

Great thanks for this plugin!!!!!!

**mezz64** · 11-17-2008, 03:22 PM

Originally Posted by NiMar

Now the result of short testing:
1. For Russian regional settings there must be ","as separator in ini. for example: LITERS=2,5
2. Connected indicator doesn't work for me

don't know why.
3. Arrows on flash gauges and digital value on them sometimes doesn't match. i.e. arrow show on 30, but numeric value is 5.
4. Sometimes Arrows on flash gauges start slowly to rising, but the value is not changed.
5. Several times Vehicle speed freezed on some value(i.e. 30) and doesn't change even when car is stopped. i reconnected ELM to car at it became working.

1. Good to know!
2. Are you using a new RR build?
3. This might have something to do with the "," again. I tested all gauges for both english and metric and they seemed to work fine. It would be great if someone using english settings could report their findings on this.
4. Again, I think it's the ",". In order for the flash to work I have to strip off the units and round the number, i think with a comma instead of a period the flash round function fails.
5. Was this with the flash gauges or just in general?

As for the suggestions:
1. Changeable colors more than likely won't be happening, at least not for this skin. As I mentioned in my early post the flash was just a proof of concept, my design efforts are going towards my own skin at the moment.
2. I'm pulling PID's every 1/4th of a second right now, any faster and I get blank data. You should notice a speed increase if you turn off ExtraOBD and only pull the values needed for fuel efficiency calculation.
3. Should be able to make that an ini option. I'll put it in the next release.

Thanks for the comments!

**Sonicxtacy02** · 11-17-2008, 06:18 PM

i took a sec to run the plugin and it worked pretty darn well! I do have a question though. With MAF= False the maf label displays data, but with maf = True the label stays at 0. I'm not sure if the car has a MAF or not but the MAP label is populating so i'm assuming not. All other sensors that work with scantool.net work with this plugin. Cant wait to see how accurate the MPG turns out. Great work.