%META:TOPICINFO{author="blundar" date="1078515420" format="1.0" version="1.1"}%
The Manifold Absolute Pressure Sensor (Map Sensor) tells the ECU what the absolute pressure in the intake manifold is (relative to Absolute Vacuum). This allows the ECU to calculate the amount of air entering the engine, in order to determine how much fuel to inject. It is slightly less accurate than a Mass Air Flow system. A Maf Sensor, which directly measures the amount of air, will more directly take into consideration air density.
All Honda PGMFI systems use the Speed Density approach utilizing a Map Sensor.
Joesph Davis had this to say about the stock map sensor:
"MAP sensor: It is a 1.8 bar absolute sensor, not 1.7. It is linear for pressure:voltage, so graph it out via these two points: key on, motor off and a boost value.
Stock 1.8 bar sensor = 2.85 volts with key on engine off and 4.5xx volts at 10.6 psi. Due to physical construction, which limits MAP sensor diaphragm travel so that the full 5 volt referrence voltage return is never acheived, you never read past 9.25 psi OBD0 and 10.65 psi OBD1 ."
Map Sensor Equation
GM 2Bar, 2.25Bar and 3Bar MAP sensors can all be calibrated/graphed in a similar manner - measure voltage with key on but engine off (~= 14.5psi Absolute Pressure - one atmosphere) and then measure voltage at a known boost level, calculate slope and plot!
GM 3bar sensors read ~1.6volts key on / motor off.
GM Map Sensor Identification
this picture has been taken from:
http://www.robietherobot.com/storm/mapsensor.htm
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%META:FILEATTACHMENT{name="gm_mapsensor.jpg" attr="h" comment="Identifying GM MAP sensors" date="1078515234" path="C:\Documents and Settings\Administrator\Desktop\temp\wiki\gm_mapsensor.jpg" size="28687" user="blundar" version="1.1"}% |