Calculate MPG for Ford Diesel - Diesel Truck Forum -
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post #1 of 2 (permalink) Old 11-25-2014, 05:28 PM Thread Starter
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Calculate MPG for Ford Diesel

For gas engine, MPG is usually calucalted by using MAF (Mass air flow) PID, because gas engine has fix air to gas ratio (AFR). However diesel engine doesn't have fix ratio so that method won't work.

For Ford 6.0 there is PID for Mass Fuel Desired which can be used for MPG: Mass Fuel Desired (MG/str) * Engine Cylinders / 2(for four stroke engine) * RPM * 60(to calculate fuel used per hour) / 1000(convert mg to gram) / 832(diesel density is 832g per liter)

In L/100kM:
8 cylinder engine(L/100kM): [Mass fuel desired] * [RPM] / [Vehicle speed] * 0.0288461538461538
6 cylinder engine(L/100kM): [Mass fuel desired] * [RPM] / [Vehicle speed] * 0.0216346153846154

Or in MPG:
8 cylinder engine(MPG): 8154.12 * [Vehicle speed] / ([Mass Fuel Desired] * [RPM])
6 cylinder engine(MPG): 10872.16 * [Vehicle speed] / ([Mass Fuel Desired] * [RPM])

To prevent divided by zero in the formula, you can add small number to denominator. Here is the PID file that can be used in Engine Link iPhone app:

010D,Vehicle speed,0,255,km/h,A,0
221412,Mass Fuel Desired,0,100,mg/stroke,(A*256+B)*0.0625,0
,MPG(8 cylinder),0,100,MPG,8154.12 * [Vehicle speed] / ([Mass Fuel Desired]*[RPM]+0.01),0
,MPG(6 cylinder),0,100,MPG,10872.16 * [Vehicle speed] / ([Mass Fuel Desired]*[RPM]+0.01),0

Engine Link is a highly customizable, inexpensive option for monitoring all of the critical parameters on the Ford 6.0L.
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post #2 of 2 (permalink) Old 11-26-2014, 06:30 PM
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So is this how you plan to market your app for the iPhone, spam the forums with a bunch of calculations to make it look like you've figured it out?

How are you planning to calculate the fuel used during the variable operating conditions of the injector, or rather, where are you getting the exact flow data for the nozzle at the infinitely variable pressures and pulsewidth the engine can operate under? Due to the nature of the injection system on 7.3 and 6.0 Powerstrokes, there is such a broad range of injection pressure and pulsewidth that without a 3D map of measured injector flow for a given injector specification,your method will never properly or accurately calculate fuel used.

The only way to properly calculate fuel mileage on a 6.0L (actually on a majority of applications) would be to install flow meters on the fuel feed (and fuel return lines if equipped), comparing the flow data would show precisely how much fuel is used under any given operating condition and allow instant and average fuel consumption rates. No vehicle comes with a fuel flow meter.

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