Air Flow Measurement

[Mazda Ebrahimi]

> Still seems to me (I'm still fishing for a definitive answer) that
> TPS, BAP, MAP and TEMP (IAT) would give a very reasonable approximation
> (after correction for non-linear TPS vs. opening area) of MAF.  No ???
> 
> Tom Cloud <cloud at peaches.ph.utexas.edu>

Yes.  But don't forget the idle air bypass motor.  Also, what the automotive 
manufacturers do with their sensors is not necessarily just for air mass flow 
calculations.  Even if they decided to do away with MAP in air mass flow calculations, 
they would still need it or another way of determining EGR rate for diagnostics.
Here is another important point:  Under part throttle conditions, air mass flow is 
greatly affected by throttle angle and pressure drop accross the throttle blade.  This 
affect is the dominant factor in determining air mass flow.  By contrast, the closer we 
get to WOT, the more actual air mass flow is affected by the dynamics of the engine 
(intake runner length, plenum volume, cams, etc), and the less it is affected by 
pressure drop across the throttle.  So it would make sense to use a weighing system to 
base mass flow calculation based on throttle angle at lower manifold pressures, and base 
it on MAP the closer we get to WOT. Right?

I know this is getting too detailed.  The bottom line is that you CAN use TPS instead of 
MAP. and yes, you do need intake air temp regardless.

Chow for now
Mazda Ebrahimi