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ss2115
03-04-2021, 08:28 PM
Hi.

For some time now, my dash reading of fuel consumption has never tallied with the actual.
My dash usually reads between 15 and 16.5 liters per 100klms while my actual (ie: fill-up, make the liters/klms traveled calculation) is usually around 12 - 12.5.

I've Torque installed on my android media display and a matching Blutooth OSDII plugged in and I've observed my Long Term trim is 3.48 and 2.78 while the STT usually hovers around 0.770 up to 1.1 or so.

My actual problem though is I've used the hidden menu hack to try changing my fuel multiplier, but it doesn't matter if I'm down around 780 or if I'm up at 1200, the fuel display when reset starts around the 12l/100k but over a tank still ends up displaying around 16 - 16.5. Its quite weird because you would expect in one direction my consumption would be understated and in the other direction overstated. Yet it always comes out the same.

I've used a laptop with the BMW OBDII software and I don't have any error codes. (I thought maybe the O2 sensors might be out of range) but no errors. The MAF is only about 2.5 years old.
Additionally, in Torque when driving is tells me the engine is in closed loop and when the O2 sensors are being observed, they swing correctly back and forth between about 0.1 to 0.85 or so.

ie: I don't think its my O2 sensors casing the problem although to my knowledge, they have never been replaced.
How can it be when I do the actual calculations and it comes out much lower than being displayed anyway - ie: if the O2 sensors were to blame, my actual measured figures would show high fuel consumption.

Any advice on how to correct this would be greatly appreciated. Its not so much that I'm a careful or frugal driver or such - its more than I'd like my fuel range remaining to be accurate.

Car is a late 2002 E39 530i s/wagon. No engine mods. Its in great condition and has only 135,000 genuine klms on it. I'm the second owner.

edjack
03-05-2021, 11:12 PM
Why do you care? Just fill it up when low, and calculate the fuel consumption with arithmetic.

The Germans have tried to be clever, but it sometimes doesn't work.

JimLev
03-06-2021, 08:51 AM
ss2115, mine was reading about 2 more MPG than actual, pretty sure they all do. I changed the fuel multiplier and now it reads within .1-.2 MPG from actual.

jclausen
03-06-2021, 09:19 AM
22.4 mpg

ss2115
03-14-2021, 06:01 PM
ss2115, mine was reading about 2 more MPG than actual, pretty sure they all do. I changed the fuel multiplier and now it reads within .1-.2 MPG from actual.

Thats what I'd like to do as well. But I'm not in a fuel consumption competition or needing to know that figure as much as edjack seems to think - I just would like to get my 'klms till empty' reading a lot closer than it is and that involves getting the fuel consumption closer than it is.
And thats the problem - adjusting my fuel multiplier doesn't seem to be making any difference and in fact the consumption it shows is not anywhere even close to what I'm actually getting no matter what adjustment I make. Thats what I'm trying to solve and had hoped to get some help with.
Why does adjusting my fuel multiplier give such a huge swing to high consumption in both directions either side of 1000? One would think in one direction it would understate the consumption and in the other overstate it. But mine for some reason drastically overstates it in both directions!
I did the maths after a couple of tanks and the multiplier I came up with should have been 878. But it increased the display reading. So I thought maybe I'd gone the wrong way and I tried 1122 but it still displayed a high reading. It doesn't make sense.
So I went huge numbers in each direction - 760 and 1200 just to observe the results and over a full tank each they both come up with even higher consumption figures. Still doesn't make sense.