MAF and SD

[Dale Ulan]

> It doesn't matter what the ambient air density is.  Air density in the
> intake manifold is all that matters.

Yes, except that the other end of the engine sees barometric pressure...
ie. the end of the exhaust pipe.

> GM speed density uses only MAP.  Did Ford's aborted attempt at speed
> density use a BAP sensor?  (the worst comments I've heard about that
> system have all come from Dearborn :)

Yea, but if you look at the code, it finds BARO using the MAP sensor
under certain conditions. In fact... 
RPM < $C0 ($FF = 6400 rpm)
TPS > $A6
DTPS < $05 (don't remember the sample time...)
then MAP -> BARO via some wierd transfer function involving TPS...
here's the table.
FF EC 55 2B 1B

Then, it uses the BARO to play with the POWER threshold (baro-
corrected TPS), and EGR flow rates. It also has a table ranging
from $88 to $80, multiplying the BPC, which appears to be the
compensator for exhaust pipe backpressure vs. BARO.

-Dale