Thread: SG2 vs TDI
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Old 06-21-2010, 03:59 PM   #4 (permalink)
ChrstphrR
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Join Date: Jul 2008
Location: Sault Ste Marie, ON, Canada
Posts: 128

Schwartzejetta - '00 Volkswagen Jetta TDI GL
90 day: 52.87 mpg (US)
Thanks: 19
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Quote:
Originally Posted by tasdrouille View Post
What settings did you use to get the fuel consumption right?
I'll give a run down of what I HAVE tried, alas without extensive data to show with it:

There's no ideal settings I've tried that work in all cases: The TDI ecu does seem to pull some trickery that the Diesel1/Diesel2 fuel types from the SG2 settings can't compensate for.

I've also tried adjusting the mileage counted out, to match distances, but I still ended up with inconsistent errors.
(There's another setting to adjust that, but I can't remember the option to get to it, but it is in the same sets of screens as setting the engine / fuel / display /etc.)


And, finally, what I do to compensate:
  • Keep a pen and paper with me when filling up, and optionally, a cell phone with a calculator app.
  • Record actual Odometer readings (I use the trip odometer since it will go to the 10th of a kilometer)
  • Record the Tank mileage, distance, volume of fuel consumed, etc.
  • Figure out the actual mileage based on my fuel receipt.
  • Figure out the ratio of (Odometer distance/SG2 Tank distance)
  • This yields a number (say, 1.04) that I use...
  • when I go to the Fillup screen on the SG2, I *divide* the SG2 expected fuel amount on screen by the ratio of distances, to make my adjustment.
  • And here's where the non-math based reasoning happens: City driving yields a different mileage than highway for my TDI, so, if I had an all Highway tank, and expecting a city tank, I'll adjust accordingly... or vice versa.

This seems to make the tankfuls I tracked wobble about the "ideal", and long term, it handles perturbations like doing a cross-Canada trip, then only do in-town driving for the next few tanks.

But you have to do your judgement on what your future driving will be on the current fill-up to keep from swinging well past 5% over/under. Sometimes that's not easy to predict.

Perhaps I just wasn't patient enough with calibrating with the distance/odometer correction first. It's hard to be that patient to try more than two-three tankfuls to calibrate, when each tank is now lasting me around 5-6 weeks!
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