algorithms

[Mike Klopfer]

>This is the equation Bicking gives for calculating Mass Flow Rate using
>speed-density.
>
>Known		V   = Per-cylinder Nominal Displacement
>Known		Ra  = Gas Constant of Air
>Measured	RPM = Engine Speed
>Measured	Ta  = Intake Air Temperature
>Measured	P   = Intake Manifold Pressure
>		n   = Volumetric Effieciency
>Calculated	Ma  = Mass Flow Rate
>
>
>	Ma = (RPM)*V*n*P
>	      ---------
>	      (Ra)*(Ta)
>
>Here are questions I have.
>
>1)  What is meant by the Gas Constant of Air?
>
>2)  How does one determine volumetric efficiency?
>
>3)  Once this equation is worked out, you have a good
>    starting point to derive a base pulse width, Right?
>    Now how do you factor in things like Throttle
>    Position Sensor, and Coolant Temperature Sensor?
>


I believe that Ra is most likely the ideal gas constant. A couple of papers
SAE 93085? "Transient A/F Ratio Errors in Conventional SI Engine Control",
SAE 900616 "Mean Value Modelling of Spark Ignition Engines " give a good
description including mathematical equations for the mass flow as a function of
throttle position, manifold pressure and rpm. In these equations volumetric
efficiency is a quadratic function of rpm and a linear function of P. In a
earlier post I tried to describe my best guess on how one might be able to
estimate the various constants in these equations for a given engine. I don't
know how practical or even understandable it is but if you'd like I could find
a copy pretty easy.

mike
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