Fuel consumption correction factor

Hi Jani, since I use only a tablet via OBD 2 BT dongle my avg fuel consumption is not very accurate. So, when I do city driving I change the Fuel consumption correction factor to 0.28 and in Highway I keep it at .45 to .48.

Currently, I have to go into garage and change it while driving. Can I create a button to change that value from the dashboard? If it’s not there can you enable that feature?

Alternatively, if you can add it to the quick settings, it will help.


I think better solution would be try to make fuel consumption calculation more accurate. First thing to check is to see if all engine settings are correct in the garage. On OBD2, engine size, VE, injectors count etc may have effect on consumption calculation. You could try to tweak the VE of the engine as that as non-linear effect on the consumption calculations.

Yes the engine parameters are correct. It is a BMW 320d LCI model.

What I haven’t changed since I couldn’t find anything on the internet are:

Volumetric efficiency is set as 80% (perhaps it was the default) .
FCC factor default was 0.33 (I change it to 0.28 for city and .45 for highway)
Mechanical efficiency is at 95%
Drag coefficient is 0.26
Rolling resistance is .02

Not sure what is ideal but will play around with VE to see if it makes any difference.

If you have any suggestions, pls let me know.

I think 320d uses a MAF sensor for fuel consumption calculation. Have you checked that you are getting proper MAF sensor readings?

Not sure, pls guide me on how to check it!

Just edit a dash, add a text gauge and link it to MAF to see the g/sec reading.

Ok will check and report.

Is there any specific value I should look for?

I am getting the following readings:

Idle : 7 (constant)
Coasting (Eco mode) : 7 (constant)
While taking the leg off the accelerator it shows 16-17 (mostly constant)
While accelerating it starts increasing and saw a reading as high as 60 (under heavy acceleration)
Range is from 7 to 60 and values keep changing as I accelerate.

Is this ok, Jani?

BTW, for different VE % I am having to tweak the FCC as follows to match the car’s Mid reading (kmpl):

With Volume efficiency at 80%: Fuel consumption correction factor: 0.28 in City driving (to get close to mid reading)
With Volume efficiency at 90% the FCC for city is 0.33 (to get close to mid reading)
With Volume efficiency at 100% the FCC for city is 0.34 (to get close to mid reading)

But my worry is when I go on a highway for long drives will I need to make it around 0.45 like before to match the car’s mid reading.

Basically, FCC has to be set as lower value for city speeds and has to be set as higher value for highway speeds at a level of VE %. I have tested this at 80% VE but need to see at 90% or 100%.

If FCC can be set at one value for all driving conditions then no worries at all.

Jani, is MAF working ok?

Any suggestions on FCC?

MAF values seem reasonable for me.

One more check, have you set the fuel to Diesel at the garage? Fuel settings are in the trunk of the car.

Yes Diesel (AFR 14.50).

So, VE at 100% is correct?

How do I get it right, Jani?

I don’t know. This is how much I can help remotely, sorry :frowning:

Ok thanks!