GM MAP sensors

[pishta]

GM has 1,2,and 3 bar MAP sensors that are OEM on their products. The MAP part numbers (not complete):
3 digit numbers for identification:
1 Bar: 039, 460, 883, 876, 153, 719 (green connector?)
2 Bar: 886, 012, 539, 609, 701, 539 (tan connector?)
3 Bar: 749, 861

The 2 and 3 BAR sensors have a unique key system in the connector. If the center socket has a vertical key in it, its a 2 or 3 BAR sensor. If there is no key in the center socket its a 1 BAR. Orientation when mounting is important. Mount so the nipple is facing <30 degrees from down so as to prevent moisture from pooling from condensation. Also recommended to mount higher than intake. I found a 2 BAR MAP on a supercharged Pontiac Bonneville. They are not that uncommon in US junkyards. Its mounted right behind the supercharger on a bracket, just follow the hard pressure line from under the pulley and is held on by a T20 torx bolt but a good pair of pliers can grip the bolt and unscrew as the torque spec is low to prevent deformation of the case.

This is example of "no key" 1 BAR sensor socket. Suitable for all reference external MAP sensors

[Fred]

This thread needs self-verified calibrations for each size! And possibly tolerance based calibrations, too, if available.

[pishta]

Im on it. I can only do voltage out at various pressures at 70F if i can get a solid 5.1v out of my almost complete jaguar board. Will attempt tonight.

[Fred]

5.1 is a terrible choice as they're probably ratiometric. But as long as you record your exact voltage, it's fine. Aim for 5.000000 :-p I've seen 5.05 and 5.01 and 4.99 out of these regs. Moving this thread to general hw, too.

[pishta]

Ok, better late than never!

719 1 bar sensor in in-HG vac taken at 70F with reference voltage 5.11. (as close as I could get to 5.00 with what I had)
23 in .78v
22 in .91
21 in 1.05
20 in 1.22
19 in 1.41
18 in 1.63
17 in 1.78
16 in 1.98
15 in 2.16
14 in 2.36
13 in 2.54
12 in
11 in 2.89
10 in 3.08
9 in 3.27
8 in 3.46
7 in 3.66
6 in 3.86
5 in 4.06
4 in 4.26
3 in 4.46
2 in 4.67
0 in 5.00

2 bar 539 map
23 in
22 in .45
21 in .54
20 in .61
19 in .70
18 in .78
17 in .86
16 in .95
15 in 1.04
14 in 1.12
13 in 1.21
12 in 1.30
11 in 1.38
10 in 1.46
9 in 1.55
8 in 1.64
7 in 1.73
6 in 1.83
5 in 1.97
4 in 2.01
3 in 2.11
2 in 2.22
0 in 2.37
No boost data yet, trying to figure how Ill pressurize it with an accurate gauge.

[Fred]

Nice work! :-)

[pishta]

After sleeping on it, I realized the 0 output on the 1 BAR is exactly 5.00V. Ill use that as the source voltage and retest the 2 BAR map and see if the voltages are truly proportional with the input voltage, along with a little boost pressure sample from a hand pump.

[pishta]

here is a 2-3 BAR MAP output graph for GM part numbers


here is my recordings using crude vacuum gauge and DMM. Supply voltage was within GM specs of 5.1V +- .36V



freescale is linear from 4.75V@250kpa (2.5BAR or 22 psi)) 1.75V@ 100kpa (0 vacuum sea level) down to .30V@20kpa (28in vacuum)@ 5.1V sorry I didnt have time to convert kpa to in/hg