Skepticism of exceptionally high Scanguage numbers?

[smartzuuk]

I am a little bit skeptical of exceptionally high Scanguage numbers.

Although I have calibrated to within 1%, and it does match my pen and paper results *almost all* of the time, I have noted a few quirks.

Namely, I was able to get the live fuel economy display to toggle between 90.0 MPG and 120 MPG for many miles with cruise control applied during a flat stretch, with NO other number showing! You can see this in the short video clip below, and also note the current trip FE of 103 mpg:

http://www.100mpg.ca/wp-content/sg-quirk-120mpg.avi

During the same trip, I was able to get Scanguage to toggle between 113 mpg and 170 mpg, again, for many miles:

http://www.100mpg.ca/wp-content/sg-quirk-170mpg.avi

Your thoughts?

[JanGeo]

That is normal because of the resolution that the SG has to calculate with . . . since the fuel burn rate is 0.1gph then you only get that resolution so numbers like 300mpg at 30mph at 0.1gph burn rate will drop to 150mpg at 0.2gph - the typical burn rates for my xB when in neutral and idling.

[smartzuuk]

I'm not understanding clearly what you mean. Are you saying that the FE number is based on the 'burn rate'? (GPH) I would be very surprised if that were the case.

[Compaq888]

The FE number is not always based on GPH. Sometimes I spend more fuel but I get more fuel economy. Where that happens is when you hit the sweet spot of the engine.

Even with the scangauge I still can't figure out how much TPS the car should be at to get the best fuel economy on the freeway.

My car is very very sensitive to every incline and decline, even with the scangauge I can't figure this out. I need an airport runway to figure everything out.

Also don't trust your scangauge to much. My scangauge has been accurate within .1 of a gallon. Last 2 tanks were really weird. It was off by .9 of a gallon and .2 of a gallon. It's a good thing I got gas because I had maybe a couple more feet and would of had to push my car. I got my entire tank capacity and then some when I filled up.

[JanGeo]

Hooo that sounds like a pumping error on the pump meter.

The average FE for the trip is more accurate because it used the fuel used over the many miles driven so it can calculate to x.1mpg but the smallest unit of measurement of the rate of fuel that you are using is 0.1gph at 25mph = 250mpg which when used to calculate the instant MPG turns out to be not very accurate i.e. if you are really bunring 0.11gph at 25mph = 227.27mpg then it would calculate more accurately but apparently it doesn't have that precision.

[MetroMPG]

This sounds like a question to ask Ron at Linear Logic. I've always found him to be very responsive to specific questions.

I've also seen this behaviour. On a recent trip with the car warmed up, flat roads, negligible wind, approx 45-50 mph, I watched the SG "instant" screen toggling exclusively between 66 mpg and 83 mpg (no intermediate values), and I could influence which I saw with an imperceptible movement of the throttle.

[Ted Hart]

Originally Posted by MetroMPG

This sounds like a question to ask Ron at Linear Logic. I've always found him to be very responsive to specific questions.

I've also seen this behaviour. On a recent trip with the car warmed up, flat roads, negligible wind, approx 45-50 mph, I watched the SG "instant" screen toggling exclusively between 66 mpg and 83 mpg (no intermediate values), and I could influence which I saw with an imperceptible movement of the throttle.

Well! Someone finally sees the light! The Scangauge is merely a voltage...computed from other voltages (GPM, RPM, velocity,etc.). I have always had my doubts about these variables and how they are generated. Someone put together a circuit board which computes (divides / multiplies) these & gives a final voltage ... a number on the screen.
But... one has to consider the accuracy of these inputs. Traditionally, they don't reflect the real world (as seen in the grossly inaccurate swinging of the numbers)! Comments?

[Ted Hart]

Originally Posted by JanGeo

Hooo that sounds like a pumping error on the pump meter.

My goodness! You dare to compare the accuracy of a Scanguage to a state-monitored / calibrated pumping mechanism? I don't think so....

[Compaq888]

Originally Posted by Ted Hart

My goodness! You dare to compare the accuracy of a Scanguage to a state-monitored / calibrated pumping mechanism? I don't think so....

dude please. it's easy to rig the pumping mechanism just like it was easy to rig the 2000 and 2004 elections. Anything electronic can be rigged.

[MetroMPG]

Originally Posted by Ted Hart

But... one has to consider the accuracy of these inputs. Traditionally, they don't reflect the real world (as seen in the grossly inaccurate swinging of the numbers)! Comments?

My comment: despite the instant mpg behaviour specifically described above, once my SG1 was calibrated, it was always within 2% of actual at fill-up time, and normally less than 1%.

The overall accuracy of the thing isn't in question.

I'm with JanGeo on this: I don't typically put much stock in the instant figures anyway. Tank & trip averages are what I watch.

Still the "toggling" between values in instant mode is peculiar, and it would be nice to know what Ron DeLong has to say. Are you going to contact him, smartzuuk?