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...

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

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.

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.

Good point about moving speed being useful for MPG.

OK, may I rephrase? Ideally, I'd like be able to view average speed calculated by different methods. :)

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.

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.

Only in pseudocode: if speed > 0, update average

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