factory instrumentation accuracy & mpg

[Ti Kan]

Steve Beeler writes:
> Does anyone know how the driving computer arrives at the number it calls av=
> erage MPG?  It definately has NOTHING to do with actual fuel flow!

The trip computer MPG display does calculate based on the fuel flow
and miles travelled.  On CIS models, either a potentiometer on the
air flow sensor or manifold vacuum sensor provide fuel flow data,
whereas on EFI and pulsed Motronic systems, the ECU meters fuel injection
quantity so that data is already available.

> Is there any way to recalibrate it?

On some models there are dip switches in the instrument cluster
that allows some range of calibration.

-Ti
2003 A4 1.8T multitronic
2001 S4 biturbo 6-sp
1984 5000S turbo
1980 4000 2.0 5-sp
--
    ///  Ti Kan                Vorsprung durch Technik
   ///   AMB Laboratories, Sunnyvale, CA. USA
  ///    ti at amb.org
 //////  http://www.amb.org/ti/
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