Air Flow Measurement or Estimation and Fuel Quantity

[Anthony Tsakiris]

>With all of this talk about air flow, could some one please just give me the
>actual working equations for calculating the quantity of fuel required based
>on either the MAF or MAP or TPS methods.  I need something to work with.


Preface:  The following is generic information obtainable from
          any textbook on internal combustion engines. 

Let,

 .
 ma = mass flow rate of air
 .
 mf = mass flow rate of fuel

 AFR = air-fuel ratio
       .  . 
     = ma/mf

     = ma/mf  when the rates are integrated over the
              same time period, say an engine cycle or
              cylinder event

 AFRs = stoichiometric air-fuel ratio

 L = relative air-fuel ratio (relative to stiochiometry) 
   = lambda
   = AFR/AFRs
     (L < 1 means rich, L > 1 means lean)

Then,

 mf = ma/AFR

    = ma/(L*AFRs)

L is an independent variable with a value determined based
on what the requirement of the engine is (torque, fuel economy,
emissions, ...).

AFRs is a characteristic of the type of fuel, typically taken to
be ~14.7 for air and gasoline.

So ma is needed in order to determine mf.

ma can be measured directly or estimated.  ma and mf should be 
consistent in time and location.



Helpful?


Anthony Tsakiris

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