Saab automobiles

February 27, 2010

'95 9000 Trip Computer Accuracy

Filed under: Uncategorized — admin @ 2:53 pm

My trip computer loses 1 mile per 25 miles when compared to the highway
mile-markers. If I travel 25 miles (as measured by the mileposts) my
trip computer registers only 24.  Is this within normal accuracy range?
I assume that the computer is also miscalculating miles-per-gallon and
other measurements.
Is the computer tied into the car’s mechanical odometer? If not, then
what/where does it get its data?

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2 Comments »

  1. epows…@my-deja.com wrote:
    > My trip computer loses 1 mile per 25 miles when compared to the highway
    > mile-markers. If I travel 25 miles (as measured by the mileposts) my
    > trip computer registers only 24.  Is this within normal accuracy range?
    > I assume that the computer is also miscalculating miles-per-gallon and
    > other measurements.
    > Is the computer tied into the car’s mechanical odometer? If not, then
    > what/where does it get its data?

    It’s tied to the speedometer, but regardless… this isn’t that inaccurate
    in my experience… my Aero looses about the same.  Most cars have 2-4MPH
    inaccuracies at 60MPH… almost always reading high for the speed
    they’re going.  Mile markers TEND to be accurate.  The only speedometers
    that I’ve seen which are dead on accurate are the ones in cop-cars :-)
    They have to becertified, tested, and then they’re sealed, and then
    have to be retested every year I think.

    Anyway, the reason is multifold… inaccuracies in the mechanical parts
    of the system, but also the bigger one, differences in tire-height.

    Chris

    | Christopher Petrilli                      “Television is bubble-gum for
    | petri…@amber.org                          the mind.”-Frank Lloyd Wright

    Comment by admin — February 27, 2010 @ 2:53 pm

  2. > It’s tied to the speedometer, but regardless… this isn’t that inaccurate
    > in my experience… my Aero looses about the same.  Most cars have 2-4MPH
    > inaccuracies at 60MPH… almost always reading high for the speed
    > they’re going.

    My ’91 9KT’s speedo was accurate when fitted with the stock 205-50ZR-16 tires,
    but when I changed to 205-55′s from then on the speedo became about 5% fast.  My
    ’95 Aero has 205-55′s as well, and it’s also fast.

    I’ve noticed, though, that when I reset the "average speed" setting on the trip
    computer, it is very close to correct.  When the cruise is set to 80 mph on the
    speedo, the "average speed" shows 75 mph.

    Comment by admin — February 27, 2010 @ 2:53 pm

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