Average MPG Calculations on Dashboard

hoarec · May 6, 2011

OK, heres one for the techies........How does the car calculate the average MPG that is displays on the dash??

I know that they are not very accurate, however mine has just gone haywire and is reading anywhere between 48 & 99 MPG when I reset it....once it reaches 99.9 it then starts to go down again....if it was real I would not mind

, but as I have to keep filling up I have my suspicions that it is telling me lies.....

I assume that it is a symptom of a component failure somewhere...MAF, O2 Sensor, fuel regulator or some other fuel/emissions related gadget.....:doh:

Regards

Chris

jonasserra · May 6, 2011

In the Owner Manual, pg 116

"Average fuel consumption
This function is automatic and indicates the average fuel consumption since the last time the trip computer was reset (average fuel consumption is calculated by dividing the distance travelled by the amount of fuel used).
While the system is calculating the average fuel consumption, the display shows
’COMPUTING MPG’. Once the fuel consumption value is calculated, ’AVERAGE
MPG’ will be displayed, and a 3 digit fuel consumption value (shown in tens, units and tenths of a gallon) also appears in the display
NOTE: The displayed value will not change at a rate greater than 0.1 litres/100 km per 6 seconds, and will be between 0 and 99.9litres/100 km."

362bkr · May 6, 2011

hoarec said:
OK, heres one for the techies........How does the car calculate the average MPG that is displays on the dash??

I know that they are not very accurate, however mine has just gone haywire and is reading anywhere between 48 & 99 MPG when I reset it....once it reaches 99.9 it then starts to go down again....if it was real I would not mind, but as I have to keep filling up I have my suspicions that it is telling me lies.....

I assume that it is a symptom of a component failure somewhere...MAF, O2 Sensor, fuel regulator or some other fuel/emissions related gadget.....:doh:

Regards

Chris

How do you know its not doing 99.9 mpg ?............................I,ll get my coat.

hoarec · May 6, 2011

jonasserra said:
In the Owner Manual, pg 116

"Average fuel consumption
This function is automatic and indicates the average fuel consumption since the last time the trip computer was reset (average fuel consumption is calculated by dividing the distance travelled by the amount of fuel used).
While the system is calculating the average fuel consumption, the display shows
’COMPUTING MPG’. Once the fuel consumption value is calculated, ’AVERAGE
MPG’ will be displayed, and a 3 digit fuel consumption value (shown in tens, units and tenths of a gallon) also appears in the display
NOTE: The displayed value will not change at a rate greater than 0.1 litres/100 km per 6 seconds, and will be between 0 and 99.9litres/100 km."

Thanks, but I do not see :-"a 3 digit fuel consumption value (shown in tens, units and tenths of a gallon) also appears in the display" on my display.

What calculates the amount of fuel used? as I suspect that whateverf it is.... it is duff, also, how does this work on LPG?? what measures the amount of Gas used?

hoarec · May 6, 2011

362bkr said:
How do you know its not doing 99.9 mpg ?............................I,ll get my coat.

It might be....but if it is, I also have a leak in the fuel lines somewhere

as I still keep filling her up every two days....:doh:

hoarec · May 6, 2011

Any ideas regarding this issue yet lads????

Very quiet on the forum today, is there something happening that I don't know about??

Bromsgrove Defender · May 6, 2011

hoarec said:
Very quiet on the forum today, is there something happening that I don't know about??

Yeah most of us are working

fortgrange · May 6, 2011

As far as I'm aware the computer for mpg gets its info from regular pulses by the ECM. And as LPG has its own ECU it has no way of figuring that out. Distance to empty figures are tied in with the fuel gauge.
Pen paper and maths is still the best way of working out consumption but I've always found my trip computer to be fairly accurate (assuming you reset after every fill up) which is a bit of a shame as its only showing 12.8 at the moment:doh:

kooky_guy · May 6, 2011

fortgrange said:
As far as I'm aware the computer for mpg gets its info from regular pulses by the ECM. And as LPG has its own ECU it has no way of figuring that out. Distance to empty figures are tied in with the fuel gauge.
Pen paper and maths is still the best way of working out consumption but I've always found my trip computer to be fairly accurate (assuming you reset after every fill up) which is a bit of a shame as its only showing 12.8 at the moment:doh:

I've often wondered where it gets it's values from on lpg. Surely if it couldn't get anything at all then it would show 99.9 mpg as the car is still travelling, but not burning any petrol.

Mine says something like 24mpg, but no idea what it's basing that on or how it's calculated. I just go by the mileage on lpg.

P38_Ireland · May 6, 2011

apparently im getting 33 MPG on my DSE!!! i fookin wish!

Average MPG Calculations on Dashboard

hoarec

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362bkr

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hoarec

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hoarec

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hoarec

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fortgrange

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P38_Ireland

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