TDI scan gauge issues

Discussion in 'Fuel Economy' started by garyk, May 30, 2015.

  1. garyk

    garyk Member

    Not sure if any TDI folks can weigh in or have and idea but I thought I'd post it here. My problem is nonrandom appearance of 9999 mpg on scan gauge when accelerating. I think it's preventing me from learning the best way to drive.

    I definitely get the 9999 when coasting in gear, which makes sense as the fuel flow is shut off. This other 9999 happens sporadically during acceleration (including the pulse in my pulse and glide). I think it's the scan-gauge's way of correcting for the calibration factor I have put in, or just a glitch with the way it monitors TDI. It seems to only occur when pulsing or otherwise accelerating at a decent load, however. I've noticed if I do a slow, careful pulse, taking a long time to get up to speed, that it won't do it. It also doesn't seem to do it just driving in a steady state. Obviously the problem it makes for me is that I dont' feel I can accurately judge whether a brisker pulse is better for fuel economy than a slower pulse, since it seems the more aggressive pulses give artificially inflated overall fuel economy numbers as a decent chunk of the pulse is eaten up with a "9999".

    Right now I'm trying more like the gentler pulses I've seen recommended for TDIs here (70-80 LOD reading goal), and my scan gauge numbers look worse (when comparing same 15 mile trips), BUT if I look at overall how fast the fuel gauge is falling, it looks better than the old way! No matter what of course the actual fuel used is what matters most, but its a little harder to do tank to tank comparisons and be sure that the pulses were what made the difference, than it is to do "on the fly" shorter time frame comparisons using scan gauge.

    I'd worry similarly that if I tried to compare a steady state, driving with load kind of deal (which some seem to think is as good or better for the TDI than P and G), the pulse and glide would look artificially better given the 9999's during pulses... I think based on tank to tank comparisons that P and G does better for my commutes, but it'd be nice to be able to judge on the fly, and I dont' feel I can do that with this glitch/correction/whatever it is...

    Any ideas on how to address? It might just be a fundamental flaw with TDI and the correction factor, in which case, too bad. Its still useful for judging steady state mpg per mph etc...
     
  2. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Gary:

    Setup your ScanGauge for the "other" Diesel selection in the fuel setup. That should help.

    Wayne
     
  3. garyk

    garyk Member

    Many thanks Wayne! I have an older SGII and it does not have "other" but has "diesel A" and "diesel B". I switched to "diesel B" and it did seem to quash the 9999's. Of course now I'm getting 25 mpg ;)

    Thanks again, I'll repost if the 9999s return after calibrating. Gary
     
  4. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Gary:

    Thanks.

    Wayne
     

Share This Page