316 > 325 inaccurate Fuel reading

[bmw9818]

I've got the Obc in my car with a m40 coding plug, recently did an m20 swap I switched the plug in the cluster to the one I removed, however does the plug in the instrument cluster change fuel gauge readings? As the gauge is on the red and Obc is reading 90 miles on the range?

I have a 62 litre tank and the 325 had a 55? [/list]

Also will I need to change the plug in the Obc?

[bigwinn]

There is a bit in the wiki about recalibrating the OBC, there is a screw under a blanking grommet on the face of the OBC unit.

You will still from memory need to change the coding plug in the OBC too though

[bmw9818]

The obcs always been accurate and I havnt touched that since parking up, are there different coding plugs for the instrument clusters with larger tanks?

I thought the plugs just affect the revs...

[bigwinn]

here you go:

Inaccurate Fuel Range
The range function can be wildly optimistic at times, and needs to be recalibrated to give more realistic readings. To do this, brim the fuel tank and then remove the plastic grommet from the bottom left of the obc. Press the 1000 and 1 buttons at the same time to give a reading of how much fuel is in the tank and then turn the screw behind the grommet until it reads whatever capacity your tank is when full.

[daimlerman]

My OBC unit in the cabbie always claims that when the tank is full I can cover 460+ miles! This usually whittles down to a more realistic 360 or so within an hour or so's driving.At the other end,it will claim the tank is empty just after the light comes on in the gauge....I treat it more as a novelty item than accurate engineering.The MPG function is reasonably accurate,when you bear in mind that the thing is not calculating on just one tankful,but on all the fuel added since it was last re-set.

Gauge in the touring is reasonably accurate through most of the range,until the very end,after dropping into the red,the thing is still good for almost 100 miles,when the light comes on,my usual fillup will be about 11 gallons/50ish litres,giving the impression that there's still about 3 gallons/13 litres sloshing around in the bottom of the tank.

[bmw9818]

yep i calibrated it when i got it as it came out of a 55l and was showing 0 when gauge was showing 1/4, think thats just with the fuel tank? i tried the 1 and 1000 buttons as well says i have 12litres left,

ive allways found it pretty much bang on accurate with the m40, it goes down to 9m then just goes blank from theron ive tried it and i have about 15 miles until it conks out,

my fuel gauge on the other hand doesnt seem to be as accurate, and now its even worse!

its been showing empty for 2 days and obc reads 78m still running, i put £20 in it and only covered 69 miles since and still had about 1/4 or so in it i reckon,