Oh, I'm sure the mileage comes from the wheels, translated from revs to miles, the question was whether the conversion is before or after the accumulator that reads up to 1000. Same for the fuel---if the accumulator only accumulated whole gallons, there would be one data point every hour or two, which would be silly. I suspect that it accumulates tenth-gallons, but don't know thatince the instantaneous disply upgrades every minute, it may be that both of them upgrade every minute.

Ford was fuzzy in its answer to me, and though I have no doubt of the good will of the guy who answered, he may have as much trouble getting real information out of the designers as we do.

It wouldn't cost Ford much to set up an answer site for technical questions, and it would do wonders for their image.

And to answer your other question, I do really like the car. If I were to look into the distant future, I could see marrying a good Stirling engine with the hybrid technology, for a flexfuel option. The main argument against the Stirling engines is that they need to warm up, and won't give you a quick start out of the blocks, as people require. But the electric start would take care of that, giving you the best of both worlds. But alas, neither Bill Ford nor his successor has called me for suggestions about how to save the company.

Ah yes, and then there are steam engines, with the same handicap of a slow start. (To say nothing of occasionally blowing up, which Stirlings don't do.)

Hal

 

It actually cost them nothing....

the address is www.greenhybrid.com

 

Hi Hal

Very interesting about how the data is split into two accumulators, mileage and fuel. What is also interesting is that I've recently changed my opinion on how long in time the SG and the navi would start to drift apart. Recently, I noticed the drift just after 10 hours on the SG and navi reset. My mileage with the A/C swings from when I must keep my wife cool at all times, to when I can open the window at long stoplights when I'm alone. This as caused the SG and navi to drift even sooner.

Also, the SG and navi must convert metric to standard and they may round up and down differently. One other point, many have said the navi always reads higher. There have been many times the navi was higher part of the day, and much lower than the SG during the day. This is because data was lost in the navi and can average a faster change differently.

There is less data if any lost by the SG, so I go by it at fill-ups. I continue to monitor both to get the real story on the navi and message center.

GaryG

 

Are you familiar with all the wonderful stories about the perils of rounding when you do it wrong? The most famous is the case of the Vancouver Stock Exchange, in which incorrect rounding dropped the average over a period of nearly two years to about half of what it should have been.

I have no idea who writes these simple nav algorithms for Ford, but I'll bet a nickel we won't ever see any of them.

Hal

 

Regarding GaryG's comment about his ScanGauge and NAV MPG readings,
my ScanGuage MPG is always lower than my NAV MPG, which I attribute
to the fact that the ScanGauge simply does not understand that my FEH
is NOT consuming gasoline when in low-gear using engine compression
breaking. For example, Sunday, I returned from the local mountains,
a descent of 4,000+ feet in 18 miles; I was in low-gear the entire time.
When I started the descent, both the NAV and ScanGauge showed 33.5
MPG. At the bottom, the NAV showed 40.3 MPG, while the ScanGauge
showed only 32.5 MPG, i.e., the ScanGauge was 1 MPG LESS at the bottom
than the top of the hill!

While I like my ScanGauge, it's inability to calculate accurate FEH MPG on
anything but pancake-flat highways is particularly irksome, and makes
it an unsuitable MPG tool for much of my driving.

 

The SG has a display of GPH, which ought to be the actual fuel consumption rate in any gear on any slope under any conditions. If it doesn't read zero when no fuel is being used, something is terribly wrong. Mine always does.

Hal

 

Pretty darn sure the ScanGuage calculates fuel consumption by taking the number of strokes ( RPM ) times a certain number of microliters per stroke.

This is from observation, I have no inside engineering data.

I concur than whenever RPM's go up, even when coasting downhill, the fuel consumption rate goes up on the ScanGuage, while it goes down on the Ford Nav unit. The ScanGuage, after all, is a generic, "one size fits all" device, and one primarily designed for conventional vehicles. It cannot be expected to know the excentricities of every vehicle.

I doubt the SG gets any fuel injector data. It only infers what is being used based on certain assumptions.

I do agree that the SG changes more slowly than the Ford Nav Unit.

The 1000 value accumulators make sense, and are consistant with my observations.
I still would like to know if the sample rate is linear ( consistant, every x seconds ) or if, perhaps, it only records when there is a record worthy event, such as a change in rate. This is not far fetched. A faster sample rate would be desired during acceleration, while a slower sample rate would be desired under cruise control conditions. Thus ( just hypothesis ) in stop & go, you would fill the data bank more quickly, than you might on a long highway trip. ???