EcoModder Forum Mini test: how ScanGauge calculates average speed

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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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 Today Popular topics Other popular topics in this forum... View the most popular topics in this subforum by views or by posts
 04-13-2009, 01:21 PM #2 (permalink) Hypermiler     Join Date: Dec 2007 Location: Texas Posts: 2,320 PaleCivic (retired) - '96 Honda Civic DX Sedan 90 day: 69.2 mpg (US) PaleFit - '09 Honda Fit Sport Team HondaWagons 90 day: 44.06 mpg (US) Thanks: 611 Thanked 428 Times in 280 Posts This means that for my commute, the SG reported average speed is usually about 24 mph. In reality, I'm usually driving in the 30-40 mph range. Stops along the way drop the average. If you're planning a trip, though, it's actually a more useful metric. Any stops along the way have to be accounted for. With a 60 mph average driving speed, my highway trips are often "rated" at 50 or lower mph. The 50 mph average will tell me the actual trip time, and not some academic-paper theoretical time. __________________ 11-mile commute: 100 mpg - - - Tank: 90.2 mpg / 1191 miles
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Quote:
 Originally Posted by PaleMelanesian The 50 mph average will tell me the actual trip time, and not some academic-paper theoretical time.
Average trip speed is great for planning when to leave; not so useful if the concern is FE.
Average moving speed - down the road - relates more directly to FE.
• 150 miles @ 75 mph average moving speed; no stops = 2 hous @ 75 mph average trip speed.
• 150 miles @ 75 mph average moving speed; one 1 hr. stop (lunch) = 3 hours @ 50 mph average trip speed.

 04-13-2009, 06:49 PM #4 (permalink) Hypermiler     Join Date: Dec 2007 Location: Texas Posts: 2,320 PaleCivic (retired) - '96 Honda Civic DX Sedan 90 day: 69.2 mpg (US) PaleFit - '09 Honda Fit Sport Team HondaWagons 90 day: 44.06 mpg (US) Thanks: 611 Thanked 428 Times in 280 Posts Good point about moving speed being useful for MPG. __________________ 11-mile commute: 100 mpg - - - Tank: 90.2 mpg / 1191 miles
 04-13-2009, 11:51 PM #5 (permalink) Batman Junior     Join Date: Nov 2007 Location: 1000 Islands, Ontario, Canada Posts: 22,275 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) Thanks: 3,810 Thanked 6,690 Times in 3,468 Posts OK, may I rephrase? Ideally, I'd like be able to view average speed calculated by different methods. __________________ Honda mods: Ecomodding my \$800 Honda Fit 5-speed beater Mitsu mods: Oops, I did it again! Bought another cheap, 3-cylinder Mirage. Mods in progress... Ecodriving test: Manual vs. automatic transmission MPG showdown EcoModder has launched a forum for the efficient new Mitsubishi Mirage www.MetroMPG.com - fuel efficiency info for Geo Metro owners www.ForkenSwift.com - electric car conversion on a beer budget
 04-13-2009, 11:56 PM #6 (permalink) needs more cowbell     Join Date: Feb 2008 Location: ÿ Posts: 5,038 pimp mobile - '81 suzuki gs 250 t 90 day: 96.29 mpg (US) schnitzel - '01 Volkswagen Golf TDI 90 day: 53.56 mpg (US) Thanks: 158 Thanked 267 Times in 210 Posts Yes, but can you explain how it is accomplished and what the benefit is compared to the complexity it adds? The 1 hour break would probably not register. If it is like the guino, the current trip would reset and the tank trip would ignore such a long break (over 7 minutes). Your speed stops counting down after about 5 minutes, so that is probably the SG threshold. __________________ WINDMILLS DO NOT WORK THAT WAY!!! Last edited by dcb; 04-14-2009 at 07:20 AM..
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Quote:
 Originally Posted by dcb Yes, but can you explain how it is accomplished and what the benefit is compared to the complexity it adds?
No, but I did spend some time mulling it over on last nights drive.

I wonder if gallons/second (well actually either 0.1 gal/sec or 0.01 gal/sec) and/or gallons/second*second wouldn't be a useful (and easily calculated) metrics to see during P&G.

Batman Junior

Join Date: Nov 2007
Posts: 22,275

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)
Thanks: 3,810
Thanked 6,690 Times in 3,468 Posts
Quote:
 Originally Posted by dcb Yes, but can you explain how it is accomplished and what the benefit is compared to the complexity it adds?
Only in pseudocode: if speed > 0, update average

The benefit: it gives a nerd another data point to mull over. Isn't that enough?

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Honda mods: Ecomodding my \$800 Honda Fit 5-speed beater
Mitsu mods: Oops, I did it again! Bought another cheap, 3-cylinder Mirage. Mods in progress...
Ecodriving test: Manual vs. automatic transmission MPG showdown

EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget