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Specs:

  • App: OBDLink v5.4.1.1072 (iOS)
  • Adaptor: OBDLink MX+ (bluetooth)
  • Vehicle: 1999 Ford F250 7.3 turbo diesel (Aug 98 Production)

Have been working with this Scantool for a couple weeks now, by default the fuel economy readings are way off. Where the readings suggest that I'm never exceeding 10 MPG, basic observation of the odometer and gallons of fuel at the pump prove 13-18 MPG on average.

The most obvious source of this discrepancy I believe is located in the apps vehicle editor, specifically the following three configuration items...

  • Volumetric Efficiency (%)
  • Brake Specific Fuel Consumption (lb/hp*hr)
  • Fuel Calculation Method

Default values:

  • VE: 75
  • BSFC: 0.35
  • FCM: Intake manifold absolute pressure

I've spent a few days researching VE and BSFC and how they relate to the 7.3 Powerstroke engine, with little success deriving accurate values for this purpose.

And the FMC is a total crap shoot, where all I really have at my disposal is experimentation. Available settings include...

  • None
  • Mass air flow rate
  • Intake manifold absolute pressure
  • Direct Fuel Rate

Can anyone here identify the correct settings, with respect to fuel economy, for my vehicle?


I have determined through trial and error that "Intake manifold absolute pressure" is the only functional FCM value for my vehicle. The other three options render all default fuel economy calculators inert, only this one value produces results of any kind.

  • What do you think BSFC means? – Solar Mike Jun 25 at 21:12
  • I believe it is a measure of fuel efficiency (wikipedia), where I've seen a number of forum posts pairing this measure with torque and charting it over a power spectrum. Never seems to be referred to as a single index value. – Buffalo Rabor Jun 25 at 21:20
  • It is used to compare an engine's power output & fuel use with another engine. Given that gearing can and normally is, different between vehicles, the distance travelled even with the same engine will produce a different fuel consumption in mpg... – Solar Mike Jun 25 at 21:30

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