Date: Sun, 2 May 2004 11:05:02 +0100
From: "SAABurger" <>
Subject: Re: Fuel consumption figures computer wrong

You are right. The accuracy of the device is completely unstated. This point stimulates me to make two related points 1. On Precision and Accuracy in general In science and engineering there is a general principle that measurements (and calculations therefrom) are presented to a Precision commensurate with the precision of the data. For example, if you measure the heights of a class of children to the nearest centimetre, then the resulting data should be presented as 123cm, 129cm, 122cm etc. Presentation as 123.0cm, 129.0cm, 122.0.0cm would be considered misleading as this would imply a measurement precision of 1mm. In this light, I rather suspect that SAAB's display precision of 0.1 units (imperial-mpg, US mpg or l/100km) is somewhat inappropriate. 2. On the calibration of SAAB's on board fuel consumption calculations After a service I got the impression that the accuracy of mpg readings had improved. The computer-mpg had dropped but was significantly closer to several immediately following pump-mileage calculations. Since then, the vehicle has been serviced by an independent and I have more than an impression (over several years and 10s of 000-miles) that the computer-mpg has become ever increasingly optimistic compared with contemporaneous pump-mileage calculations. My own analysis was that: a) the device had been specifically re-calibrated , or b) the calibration of the device relies on the condition of several parts and that one or more of these had been serviced/replaced. Maybe someone with an appropriate SAAB qualification can shed some light. Hope the above is clear. Adrian "David Taylor" <> wrote in message > > That's why I said it wouldn't be perfect, but more than 6 litres is > > still an awful lot to be out by. It'd probably fill up the tank filler > > pipe several times over! > > Do Saab provide a calibration certificate for the computer or the > components in its constructions? > > I don't have one! :) > > What's the calibration and component error there? > > David. >

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