97 850 NA trip computer callibration

[dairyqueen814]

I'm inclined to rule out tire size as the problem seeing as the discrepancy is 10%.
I also am not sure if it would be the actual trip computer module because as far as I can tell the calculations that it does with the data it gets elsewhere are correct (as in the calculations of it's perceived mpg) so It would seem as though its ability to read the fuel delivery at the injectors is good.
When I first bought the car the ABS light was on so I did the home soldering fix as well as the fix where you wedge a piece of cardboard between the plug and the ABS housing. The light is off and my abs functions fine. Would that be a potential problem? If so I would think the only way to fix it would be to replace the module in which case I'll just live with the discrepancy (which appears to be very consistent)

[bmncw]

hello...

reading this thread, i just noticed that my analog trip meter and trip computer distance are different too!
1997 850 2.5 20V n/a

my analog trip meter shows between 54.5 and 54.6, so i assumed it's 54.55 Kilometers
my digital trip computer shows 59.6 Kilometers

what's wrong?

[esl_97_850_T5]

By "analog trip meter" do you mean the mechanical odometer?

What are the actual digits in the mechanical odometer now?

How are you determining the 59.6 kilometers from the digital trip computer?

Has the odometer gear ever broken?
Has the odometer gear ever been fixed?
Is the mechanical odometer incrementing now when you drive the car?

When you drive for a fixed distance of 20 to 30 kilometers, does the mechanical odometer and the digital trip computer's odometer differ by roughly 10% or are they the same (within 0.1 km)?

[bmncw]

hello... let me try to answer your questions...

By "analog trip meter" do you mean the mechanical odometer?

Yes

What are the actual digits in the mechanical odometer now?

When i wrote my reply above, it shows between 54.5 and 54.6 so i assume it is 54.55

How are you determining the 59.6 kilometers from the digital trip computer?

It is displayed on the trip computer LCD, 59.6 km, i'm in Indonesia so the odometer and trip computer uses Kilometer, not Miles.

Has the odometer gear ever broken?

I'm not sure, i got this car used from previous owner

Has the odometer gear ever been fixed?

I'm not sure, i got this car used from previous owner

Is the mechanical odometer incrementing now when you drive the car?

Yes

When you drive for a fixed distance of 20 to 30 kilometers, does the mechanical odometer and the digital trip computer's odometer differ by roughly 10% or are they the same (within 0.1 km)?

They shows a differ around 9-10%. I just drove the car today and they show 61.8 on the mechanical odometer and 67.6 on the trip computer.

I reset the mechanical trip meter and the distance in trip computer together last week when i refuel.

Last night they show:
- Mechanical trip meter = 54.5
- Digital trip computer = 59.6

Today:
- Mechanical trip meter = 61.8
- Digital trip computer = 67.6

so my digital trip computer runs 9,3% faster than my mechanical trip meter.

Thanks

[dairyqueen814]

Run some more tests and find out if it is a consistant 9.3% error because mine is a 10.4% error. on the nose every time. I still havent figured out why this is happening but at least it's consistant.

[bmncw]

Run some more tests and find out if it is a consistant 9.3% error because mine is a 10.4% error. on the nose every time. I still havent figured out why this is happening but at least it's consistant.

will do..
i'll report back on tomorrow
cheers!

[esl_97_850_T5]

bmncw,

1. I'm inclined to think you have the same problem that dairyqueen814 has -- digital Trip Computer trip odometer is reading ~10% higher than mechanical trip odometer -- regardless whether it is 9-10% or 10-11%.

2. My car has:

- a mechanical trip meter that has 4 digits representing 0.0 - 999.9, where the last digit has a different foreground/background,

- a mechanical total mileage odometer that has 6 digits representing 0 - 999999, and

- a digital Trip Computer which has 4 digits (and decimal point < 1000), representing 000.0 to 999.9 then 1000 to 9999.

3. What does your mechanical total mileage odometer say? Is it also down in the 50 - 100 range or is it up in the much more normal 50000 - 400000 range?

4. Do you have a brand new instrument cluster in the car?

5. If you have a new cluster, have you considering having a Volvo dealer to program it ****BEFORE**** you reach the 100 km mark on the mechanical total mileage odometer?

See the Blockpartie comment in this volvospeed post where he identifies 2 situations in which a VST or VST-lookalike device can program the instrument cluster. Also, you might check my 2 posts, before and after Blockpartie's post.

6. Do you have an ELM327 device? Can you read ECU 51 B901 through B90E a) preferably by using volvo850diag downloadable via volvo850diag.zip, or b) manually, interactively via the list of commands/requests at ELM327 commands to read Volvo 850/S70/V70 ECU 51 DTCs and B9nn data? I would especially be interested in knowing how your B901 - B90E values differ from previously encountered values to see if there's something in the ECU 51 B901 - B90E differences that could explain your and dairyqueen814's ~10% higher readings from the Trip Computer odometer vs. the mechanical trip odometer.

esl_97_850_T5

[bmncw]

hi esl, let me answer:

1. I'm inclined to think you have the same problem that dairyqueen814 has -- digital Trip Computer trip odometer is reading ~10% higher than mechanical trip odometer -- regardless whether it is 9-10% or 10-11%.

2. My car has:

- a mechanical trip meter that has 4 digits representing 0.0 - 999.9, where the last digit has a different foreground/background,

- a mechanical total mileage odometer that has 6 digits representing 0 - 999999, and

- a digital Trip Computer which has 4 digits (and decimal point < 1000), representing 000.0 to 999.9 then 1000 to 9999.

3. What does your mechanical total mileage odometer say? Is it also down in the 50 - 100 range or is it up in the much more normal 50000 - 400000 range?

my mechanical odometer: 096455 (6 digits kilometers)
my mechanical trip meter: 073.3 (3 digits/kilometers with 1 decimal/100 meter white background)
my digital trip computer: 80.1

4. Do you have a brand new instrument cluster in the car?

i don't know, i got this car used from previous owner

5. If you have a new cluster, have you considering having a Volvo dealer to program it ****BEFORE**** you reach the 100 km mark on the mechanical total mileage odometer?

See the Blockpartie comment in this volvospeed post where he identifies 2 situations in which a VST or VST-lookalike device can program the instrument cluster. Also, you might check my 2 posts, before and after Blockpartie's post.

i'm reading it now

6. Do you have an ELM327 device? Can you read ECU 51 B901 through B90E a) preferably by using volvo850diag downloadable via volvo850diag.zip, or b) manually, interactively via the list of commands/requests at ELM327 commands to read Volvo 850/S70/V70 ECU 51 DTCs and B9nn data? I would especially be interested in knowing how your B901 - B90E values differ from previously encountered values to see if there's something in the ECU 51 B901 - B90E differences that could explain your and dairyqueen814's ~10% higher readings from the Trip Computer odometer vs. the mechanical trip odometer.

yes i have the bluetooth elm327, and i'm reading the url now, will get back to you as soon after i try it.

my current mechanical trip meter: 73.3
my current digital trip computer: 80.1
so the trip computer runs 9.3% faster
Thanks!

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[B234R]

Very funny, this issue...in my 850 the digital trip computer is reading about 15% slower than the mechanical odometer...so the MPG function shows about 10% poorer fuel economy if I compare that with the figure I get when I fill up the tank.

I´m sure the mechanical odometer is right.

This happens since I bought my car two years and a half ago. The odometer was changed by its former owner, and the ABS module was repaired. I don´t bother too much about it, although reading the MPG display it´s always a bit depressing

[northernlights]

Mine is amazingly accurate.



This is with the highly hazardous 205/50R16 tires on OEM Columba wheels.

I started monitoring this because I am trying to figure out why my indicated fuel economy is better than I think it should be.

After my last round of super secret mods, this is where I am.



I always assumed it based the fuel consumption on airflow and distance adjusted for lambda=1, but now I'm wondering if it is based on interpolated fuel flow. To me that seems strange because the ECU doesn't really know the fuel flow number, at least not to the same extent as the signal from the MAF.

Hmm...time to find a fuel economy thread.