[Shotimes] BARO sensor

[Adam Parrott]

>> So the DPFE does NOT tell the PCM what the BP/MAP is? But BP is calculated
or inferred from the other sensors? I had it in my head that somehow the DPFE
fed a BP/MAP reading to the PCM. <<

For some reason, I used to be of the same thought (that the EEC inferred BAP
readings from the DPFE sensor or EGR system on the Gen 2 ATX cars).  It wasn't
until I consulted my EEC strategy documentation that I discovered that, on
non-BAP-equipped cars, the EEC infers it's BARO readings from other sensor
inputs (usually the MAF, ACT and TPS).

>> Now this makes me ask: If the BP can be inferred from other sensors, why
would a cheapskate like Ford spend the money to install a separate BP sensor?
<<

While there several theories floating around out there, I personally believe
the answer has to do with the fact that, at the time, the Ford engineers
relied upon these additional sensor inputs to supplement their relatively-new
mass air flow technology.  As time went on, the engineers were able to refine
the inferred strategy to the point where the MAP/BAP sensors were no longer
needed, resulting in a significant cost savings.

>> Also the SHO does NOT have a MAP sensor (and this is required) so the
inferred method seems to be missing something for our SHO's? The equation
below does not use a MAP input so maybe the MAP is not needed as an input at
all? <<

In studying several of the various EEC strategies, I have found that the
actual logic and sensor inputs used to infer barometric readings will vary
depending on the calibration or strategy in question.  Some early setups (like
some '89-'95 Mustangs) required both sensors, while others (like the '89-'95
MTX SHO) relied solely upon a BAP sensor.  Eventally, Ford ditched both
sensors altogether and looked to other sensor inputs to derive the needed
atmospheric readings (as noted above).

Adam