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Old 04-13-2009, 12:12 PM   #1 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,244

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.07 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)
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Mini test: how ScanGauge calculates average speed

The question came up in this thread about how the ScanGauge calculates average speed.

There are different ways it could be calculated, eg...

Quote:
Is the 32 mph average a true average? eg. x distance / y time = 32 mph or the mean of high and low speeds?
Another way (which I think would be the ideal measurement) is distance/time, but only where speed > 0 - meaning your moving average.

PaleM indicated he's seen his ScanGauge average speed falling while at rest (with the ignition on), so I went out and did a quick 'n' dirty test.

I reset the current trip, drove for 1 exactly minute, coming to a stop at 1:00, then recorded the average speed for 6 more minutes. Surprise - it does indeed fall while stopped, indicating a simple distance/time calculation:

Time - Avg MPH

1:00 - 13
1:15
1:30 - 9
1:45 - 8
2:00 - 7
2:15 - 6
2:30 - 5
2:45 - 5
3:00 - 4
3:15 - 4
3:30 - 4
3:45 - 3
4:00 - 3
4:15 - 3
4:30 - 3
4:45 - 2
5:00 - 2
5:15 - 2
5:30 - 2
5:45 - 2
6:00 - 2
6:15 - 2
6:30 - 2
6:45 - 2
7:00 - 2

My ScanGauge II version is 3.15

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Mitsu mods: Oops, I did it again! Bought another cheap, 3-cylinder Mirage. Mods in progress...
Ecodriving test: Manual vs. automatic transmission MPG showdown



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has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
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