Average Fuel Economy setup Km/L

General
1

How to set correct Average Fuel Economy KM/L if my diesel vehicle has MAF g/s sensor? What are the values need to enter in input mapping.

2

There is no way to adjust the average as it derives directly from instant consumption. If your instant consumption is correct, so should be the average.

The settings in the Garage that affects instant fuel consumption:

  • Engine size
  • Fuel type
  • Number of Cylinders
  • Injector size (if ECU sends injector pulse width)
  • Number of injections per cycle
  • Engine Volumetric Efficiency (with MAF)
  • Fuel Consumption Correction Factor

And here are the input data that affects the fuel consumption calculations.

  • If ‘Fuel Flow’ is received from the ECU, that is used ‘as-is’ without any other inputs.

  • Otherwise, ‘Fuel Cut’ or ‘Throttle Position’ below 1% is used to set consumption to 0.

  • Next, if ‘Injector Pulse Width’ is received, that is used to calculate fuel consumption.

  • If not, RD checks if MAF data is received, and mass air flow is used to approximate the fuel consumption

  • Next check is if MAP data is received. This is the least precise, as it uses well known approximate algorithm to calculate MAF from MAP, IAT, VE, RPM and Engine Size. Then the previous MAF algorithm is used to calculate the consumption.

If none of the above works (there is not enough data), RealDash uses internal trip diaries and added fuel in quick settings as ‘fuel diary’ and attempts to calculate the consumption based on historical data.

3

Thanks for your prompt reply.

Currently I am getting the fuel cons. avg. value in the gauge which is incorrect as per my standard vehicle consumption. if you can help me setting the values.
Standard Vehicle parameters -

  • Engine size - 1248cc
  • Fuel type - Diesel (Compression ratio 17.6:1)
  • Number of Cylinders - 4
  • Injector size (if ECU sends injector pulse width) - Unknown
  • Number of injections per cycle - 1
  • Engine Volumetric Efficiency (with MAF) - Unknown
  • Fuel Consumption Correction Factor - Unknown

Fuel flow 0 reading
MAF 8.5g/s, MAP 100Kpa at idle 15% Engine load.
Throttle position not working.

4

Hi Jani, fuel consumption has been my only grouse with RD. Nothing to do with your software I guess because I only use the ODB2 port on my 320d.

These are my settings:

  • Engine size - 1995cc
  • Fuel type - Diesel (AFR 14.50)
  • Number of Cylinders - 4 (I have set it as INLINE 4. Should I make it V4?)
  • Injector size (if ECU sends injector pulse width) - 19 lbs/hr
  • Number of injections per cycle - 1
  • Engine Volumetric Efficiency (with MAF) - 100 (tried 80 and 90 as well)
  • Fuel Consumption Correction Factor - ~0.37 for city and ~0.42 for highway (Not sure why this varies and why is impacting economy so much?)
  • Drag coefficient - 0.26 (no impact on fuel economy?)
  • Mechanical efficiency - 95% (no impact on fuel economy?)
  • Rolling resistance - 0.02 (no impact on fuel economy?)

I am not sure whether ‘Fuel Flow’ is received from the ECU. Should I try setting it in Units & Values as “Fuel Flow IS SET FROM Fuel Consumption (Instant)” or something else?

I have only set “OBD2: Fuel Level IS SET FROM Fuel Level (Calculated)”. Should I set any other parameters in Inputs and Values?

How to check Throttle position?

Any guidance to get this right will be of immense help.

Thanks!

5

The Fuel Flow is not received value from standard OBD2 connection, so it will show 0 if not coming from ECU. Also, otherwise your settings seem fine.

I’ve had reports, especially from Diesel vehicle owners that fuel consumption calculations from MAF are wrong. The problem is that I do not know what to do about it. Its just math, and trying to blindly change it to fit into some vehicle that I have no way of testing it on will just mess the calculations for those whose it is working.