After fitting an OBC over winter, I am now trying to calibrate it . At first it was showing 17MPG when I was actually getting 35ish . Now I’ve set both the OBC and the cluster setting to 750, the minimum. Run a whole tank and calculated that the MPG was around 33 but the gauge is only showing around 28 MPG. Now that both settings are set to minimum what else can I do ? Has anybody had this before ?
OBC not showing correct MPG
- Thread starter Alin S
- Start date
I honestly didn't know that those gauges were ever accurate. I'll have to check mine now!
MarkLG1973
Zorg Addict
- Joined
- Aug 28, 2021
- Points
- 49
- Model of Z
- 1999 Z3 2.8
RealOEM for the obc mentions it needs coding to the car. I’d guess the obc needs coding to the engine type?
Assuming that this is not a coding problem, setting the calibration level to 750 will certainly increase the indicated consumption. If you do have a coding problem, try increasing the MFA setting throughout its range and see if the readout changes.
It is many years since I calibrated my mpg readout, but from memory and how I understand things, the setting will tell the (basically metric) MFA of the number of metres covered when a litre of fuel has been used. This metres per litre figure is automatically converted into miles per gallon. The default setting of 1000 is presumably based on the number of metres per kilometre, while the software conversion is based on litres (about 4) per US gallon.
A minimum setting of 750 will make the MFA show that a gallon of fuel has been used in 750 metres, so giving a low mpg readout.
If we want to increase the mpg readout, it is necessary to increase the setting, so telling the MFA that the car has covered slighly more than a kilometre before a litre of fuel has been used. The mpg readout can then compared to the calculated figure, using the trip counter and the amount of fuel used to top up what was originally a really full tank. IF high or low, make an adjustment, using progressivly smaller incraments as the calculated consumption figure is approached.
With 245-40 X 17 rear tyres, my 2.8 gives a usual readout within plus/minus 1 or 2 mpg on a setting of 1021 - but after refilling at some UK petrol stations the mpg may vary, probably due to errors in the particular pump. For this reason make any adjustments based on the average calculated consumption of 2 or 3 tankfuls.
I have posted the MFA adjustment details in the Zorg 'Articles' section.
It is many years since I calibrated my mpg readout, but from memory and how I understand things, the setting will tell the (basically metric) MFA of the number of metres covered when a litre of fuel has been used. This metres per litre figure is automatically converted into miles per gallon. The default setting of 1000 is presumably based on the number of metres per kilometre, while the software conversion is based on litres (about 4) per US gallon.
A minimum setting of 750 will make the MFA show that a gallon of fuel has been used in 750 metres, so giving a low mpg readout.
If we want to increase the mpg readout, it is necessary to increase the setting, so telling the MFA that the car has covered slighly more than a kilometre before a litre of fuel has been used. The mpg readout can then compared to the calculated figure, using the trip counter and the amount of fuel used to top up what was originally a really full tank. IF high or low, make an adjustment, using progressivly smaller incraments as the calculated consumption figure is approached.
With 245-40 X 17 rear tyres, my 2.8 gives a usual readout within plus/minus 1 or 2 mpg on a setting of 1021 - but after refilling at some UK petrol stations the mpg may vary, probably due to errors in the particular pump. For this reason make any adjustments based on the average calculated consumption of 2 or 3 tankfuls.
I have posted the MFA adjustment details in the Zorg 'Articles' section.
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Thanks all. I have calculated the MFA which is needed based on the formula given by BMW and it works out that I need something around 650 , which obviously outside range . So I must assume that the OBC came from a 6 cylinder and mine being a 4 cylinder is not giving accurate readings.
has anyone re-coded the OBC from a 6 to a 4 or vice versa ?
has anyone re-coded the OBC from a 6 to a 4 or vice versa ?
Unless you are necking the fuel tank till it spills and refilling to the same level you won’t have an accurate figure of fuel used. It is the only way to be accurate.
Tony.
Tony.