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3 digit numbers for identification:
1 Bar: 039, 460, 883, 876
2 Bar: 886, 012, 539, 609, 701
3 Bar: 749, 861 |
The ECM (Electronic
Control Module) uses the Manifold Absolute Pressure (MAP) sensor to
determine the pressure of the air inside the intake manifold (engine
running) and atmospheric (barometric pressure) on start-up.
This information in conjunction with the IAT (Intake Air Temperature) is
used to determine the density of the air entering the combustion chamber.
It is also used to help adjust the IAC (Idle Air Control) during idle.
It uses a silicon wafer that is thinner in the center (0.001") than
around the edges (0.045"), which causes it to act as a diaphragm.
It is mounted with a perfect (Ha!) vacuum beneath the chip so that the air
pressure from the other side flexes the chip.
This flexing causes a change in resistance and the circuitry inside the
sensor converts this to a voltage ranging from 0.02V to 4.94V when the
output is pulled up towards 5V by the ECM .
1 Bar MAP sensors are used on NA (naturally
aspirated) vehicles.
2 Bar MAP Sensors are used on forced induction vehicles (Turbo &
Supercharged). They can measure up to 2x the atmospheric pressure(29.4psi),
so that means it can measure up to 14.7psi of boost. (Atmosphere is 14.7psi +
14.7psi from the turbo/supercharger).
3 Bar MAP sensors can measure up to 44.1psi, which translates to 29.7psi
boost from a Turbo/supercharger.
They all share a common pinout, although the connector keying may be
different:
Pin A -- Ground
Pin B -- Sensor output
Pin C -- +5 volts
MAP Sensor sources
www.SummitRacing.com
PN# MSD-2313 3bar MAP
PN# MSD-2312 2bar MAP
PN# MSD-2311 1bar MAP
www.GMPartsDirect.com
PN# 12223861 3bar MAP
PN# 16040609 2bar MAP
PN# 16137039 1bar MAP
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The chart below describes the pressure-to-voltage relationship of the
stock GM Turbo MAP sensor (2 bar):
Manifold Pressure
(relative sea level / absolute) |
2 Bar
MAP Output |
| 14.31psi / 29.01psi |
4.90V |
| 14.00psi / 28.70psi |
4.84V |
| 13.00psi / 27.70psi |
4.67V |
| 12.00psi / 26.70psi |
4.50V |
| 11.00psi / 25.70psi |
4.33V |
| 10.00psi / 24.70psi |
4.16V |
| 9.00psi / 23.70psi |
3.99V |
| 8.00psi / 22.70psi |
3.82V |
| 6.00psi / 20.70psi |
3.47V |
| 4.00psi / 18.70psi |
3.13V |
| 2.00psi / 16.70psi |
2.79V |
| 0.00psi / 14.70psi |
2.45V |
| 5.00inHg / 12.24psi |
2.03V |
| 10.00inHg / 9.78psi |
1.61V |
| 15.00inHg / 7.33psi |
1.19V |
| 20.00inHg / 4.87psi |
0.77V |
| 25.00inHg / 2.41psi |
0.35V |
| 29.10inHg / 0.40psi |
0.02V |
MAP sensor output based on altitude (Ignition
"ON" and engine "OFF")
| Altitude |
Voltage Range |
| Meters |
Feet |
|
| Below 305 |
Below 1000 |
3.8--5.5V |
| 305--610 |
1000--2000 |
3.6--5.3V |
| 610--914 |
2000-3000 |
3.5--5.1V |
| 914--1219 |
3000--4000 |
3.3--5.0V |
| 1219--1524 |
4000--5000 |
3.2--4.8V |
| 1524--1829 |
5000--6000 |
3.0--4.6V |
| 1829--2133 |
6000--7000 |
2.9--4.5V |
| 2133--2438 |
7000--8000 |
2.8--4.3V |
| 2438--2743 |
8000--9000 |
2.6--4.2V |
| 2743--3048 |
9000-10000 |
2.5--4.0V |
| Low altitude = High Pressure = High Voltage |
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