Quote:
quote:Originally posted by Big Al
Quote:
quote:Originally posted by IRPT
Refers to a manifold absolute pressure sensor, a variable resistor used to monitor the difference in pressure between the intake manifold at outside atmosphere. This information is used by the engine computer to monitor engine load (vacuum drops when the engine is under load or at wide open throttle). When the engine is under load, the computer may alter spark timing and the fuel mixture to improve performance and emissions.
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Actually - this is "absolute" pressure, which is not in relationship to the outside atmosphere. That would be relative pressure, which is what a boost gauge measures.
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From PTDIY:
The MAP serves as a PCM input, using a silicon based sensing unit, to provide data on the manifold vacuum that draws the air/fuel mixture into the combustion chamber. The PCM requires this information to determine injector pulse width and spark advance. When MAP equals
Barometric pressure, the pulse width will be at maximum.
The MAP sensor input is the number one contributor to pulse width. The most important function of the MAP sensor is to determine
barometric pressure.
Read full article here:
http://www.ptdoityourself.net/ptmapsensorguide.html
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Barometric pressure = outside atmosphere