Why your trip computer isn't accurate

[Texasota]

My numbers as recorded on the trip 344.7 158.8EV 42.6MPG low fuel light on @50. I put 10.907 Gals in. Now for the NEW MATH. If I assume correctly

344.7/10.907=31.609 this is nowhere near 42.6. 344.7-158.8EV miles =185.9 Actual gas miles driven which even worse 185.9/10.907=17.047MPG.

EV miles are time spent running on the energy that has been stored in the HVB. It is true that the HVB is charged with regenerative braking (and regen when going down hill) but the overwhelming amount of the energy stored in the HVB is via charging from the ICE (i.e. burning gasoline). And when you think about it, the energy captured during regenerative braking is coming from kinetic energy created by the ICE burning gasoline. Same is true when going downhill since the ICE expended energy by first going uphill (what goes up must come down).

 

Because of that It is not really a valid calculation of MPG to exclude EV miles.

Edited March 1, 2015 by Texasota

[mwr]

EV miles are time spent running on the energy that has been stored in the HVB. It is true that the HVB is charged with regenerative braking (and regen when going down hill) but the overwhelming amount of the energy stored in the HVB is via charging from the ICE (i.e. burning gasoline). And when you think about it, the energy captured during regenerative braking is coming from kinetic energy created by the ICE burning gasoline. Same is true when going downhill since the ICE expended energy by first going uphill (what goes up must come down).

 

Because of that It is not really a valid calculation of MPG to exclude EV miles.

Very true. Also, a valid calculation of MPG should be accomplished with both fillups done when the HVB is at the same state of charge. AFAIK, we don't have a way to know the SOC exactly, only approximately by the vertical "thermometer". But over a full tank of gas (approx 11 gallons used and 500 miles driven more or less), approximately the same SOC should be fine.

[md13ffhguy]

over a full tank of gas (approx 11 gallons used and 500 miles driven more or less), approximately the same SOC should be fine.

I don't thank anyone could calculate this variance with any granularity! The difference in SOC has to be considered negligible.

 

FYI to Bob Cooke - 500 mile tanks are coming. Many of us will achieve 600 miles with ease, come summer.

Edited March 1, 2015 by md13ffhguy

[mwr]

I don't thank anyone could calculate this variance with any granularity! The difference in SOC has to be considered negligible.

I agree for full tank and distances. For short distances, the displayed MPG varies wildly because of differences in starting and ending SOC. If you were to fill up after a short distance, that calculated MPG would also vary depending on starting and ending SOC.

Edited March 1, 2015 by mwr

[Automate]

Has anyone used the Engineering Test Mode http://fordfusionhybridforum.com/topic/6749-engineering-test-mode/and its instantaneous fuel level reading (displayed to a tenth of a percent) to determine when their fuel gauge gets to exactly 100% full?

[hybridbear]

Has anyone used the Engineering Test Mode http://fordfusionhybridforum.com/topic/6749-engineering-test-mode/and its instantaneous fuel level reading (displayed to a tenth of a percent) to determine when their fuel gauge gets to exactly 100% full?

The highest I've ever seen is 99.6 or 99.7%.

[Bob Cooke]

All righty gang, this list is from the first fill up until now

here is my list of actual vs car mpg, difference and percent off

31.67 42.6 10.99 35%

43.47 48.8 5.33 12%

41.76 53.4 11.64 28%

48.36 56.7 8.34 17%

49.20 58.1 8.90 18%

53.30 60.3 7.00 13%

52.68 63.7 11.02 21%

58.56 65.8 7.24 12%

43.12 50.7 7.58 18%

35.30 44.4 9.10 26%

45.66 54.2 8.54 19%

45.49 51.8 6.31 14%

48.56 54.2 5.64 12%

40.13 49.7 9.57 24%

33.10 38.9 5.80 18%

overall car is off by 19%

 

Edited July 7, 2015 by Bob Cooke

[hybridbear]

All righty gang, this list is from the first fill up until now

here is my list of actual vs car mpg, difference and percent off

31.67 42.6 10.99 35%

43.47 48.8 5.33 12%

41.76 53.4 11.64 28%

48.36 56.7 8.34 17%

49.20 58.1 8.90 18%

53.30 60.3 7.00 13%

52.68 63.7 11.02 21%

58.56 65.8 7.24 12%

43.12 50.7 7.58 18%

35.30 44.4 9.10 26%

45.66 54.2 8.54 19%

45.49 51.8 6.31 14%

48.56 54.2 5.64 12%

40.13 49.7 9.57 24%

33.10 38.9 5.80 18%

overall car is off by 19%

 

Do you use remote start? Any gas burned during remote start is not counted by the car and would cause these discrepancies.

[Sky14FFH]

I've been getting better than EPA (and do on all my cars) since I have owned it. Yes in the deep sub zeros of winter my MPG drops into the mid 30s but during the spring and most of the autumn I am in the low 50s and summer around 47 to 48. Anytime you use your accessories it hurts your fuel economy.

 

 

Has anyone used the Engineering Test Mode http://fordfusionhybridforum.com/topic/6749-engineering-test-mode/and its instantaneous fuel level reading (displayed to a tenth of a percent) to determine when their fuel gauge gets to exactly 100% full?

That link is dead btw. I'd like to try it though.

Edited December 23, 2016 by Sky14FFH

[mwr]

That link is dead btw. I'd like to try it though.

Here you go. http://fordfusionhybridforum.com/topic/10057-engineering-test-modedealer-test-mode

[Sky14FFH]

So is there a way to calibrate or fine tune the mpg readout on the dash on the Ford Fusion Hybrid?

[ptjones]

I don't think anyone has figured out a way to do it for FFH/CMAX. I just used a portable GPS and tracked 100 miles and the GPS said 101.8 miles so I adjust my fuelly.com mileage with actual fillup amount to figure out MPG's. :) Speedometer is about 1 mph under.

 

Paul