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Old 10-05-2012, 02:56 AM   #1 (permalink)
EcoBus Driver
tinduck's Avatar
Join Date: Oct 2011
Location: Germany
Posts: 54

EcoBus - '09 VW Multivan SL TDI 103 KW
90 day: 42.1 mpg (US)
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Problem with SG II on VW 2.0L TDI (CR) engine

Hi there,

I experience a problem with inconsistent fuel consumption given by my SG II, which I bought in October 2011.

When temperatures rose above 10 C in early spring 2012, I noticed that the comsumption values on my sg II went way up, about 20%. This was not noticable at the pump *phew*.

If you look at the momentary fuel consumption display, you got the effect that, when altering the accelerator position, consumption shows a 'realistic' value for about 1 second and then seemed to 'add' betwenn 10 and 30 % to it, with a very erratic display, wandering up and down, but always too high.

After some weeks, this problem could be correlated to outside temperatures. When temps were lower than 10 C, the display worked fine, when they went higher it acted up again.

Late summer showed that the problem is gone again above 30C.

I talked to some people on T5-Board / Board which are very good with all this ODB and CAN bus stuff. One of them - he sells modified bus control units for a living - gave me a hint that VW codes the fuel consumption and the outside temperature into the same data block on the bus, and that this can pose problems when attempting custom solutions, he himself had to work this out over time. He would not elaborate further due to IP problems, which I can understand.

I contacted the company which sells the SG II in Germany, they gave me the advice to lower my engine displacement number from 2.0 to 1.6 liters. This showed lower fuel consumption, but the offset was still there (on a lower level), and I had to go up to 30% upwards correction when fueling up to compensate, which gave me the same numbers as with 2.0 liters and +10% which I had before, so this advice was nonsense.

I communicated this whole problem with everything I found out to the scangauge guys via their contact form (in early September), but up to now these guys did not bother to answer me (or give me a 'Huh? We'll look into it' at least), which I find a bit disapointing.

In my opinion, the only way to remedy this problem would be a firmware update to extract the fuel values correctly from the bus traffic.

Until this problem is fixed, I (and everyone else with that kind of vehicle, a VW T5.2 Multivan) have to alter the compensation settings on the SG II when temperatures get lower or higher. This is OK for summer and winter, but a pain in the *** in autumn and spring, where you get lots of whacky fuel readings.

Has anyone else experienced this problem or is a solution known?




Last edited by tinduck; 10-05-2012 at 07:14 AM.. Reason: wrong date, corrected
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