MAP sensor

[acazin at interlog.com]

> I would like to add MAP sensing to my system.  What's a good MAP to use,
> how much is it, where does one get it (if it's for a vehicle, I suppose
> a parts house), and how does it work?

The Ford EEC-IV MAP sensor is a good one. It is a "smart" sensor, 
with on-board signal processing and it has digital output, a "near" 
perfect square wave (49-51 % duty cycle). It is rugged and it lives 
well in the engine compartment and a long vacuum hose from the 
intake manifold does not bother it.

Square wave output makes it easy to process. Output frequency is from 
about 159 Hz at 0 in. vacuum (key ON, engine OFF or wide open 
throttle, same as baro pressure output) to around 102 Hz at 21 in. 
vacuum (idle).

Frequency vs. vacuum output is pretty linear for a good sensor.

Alex Cazin
Alzec Automotive Enginnering Ltd.