Reading a MAP sensor

[dcb]

Here's my notes on experimenting with a map sensor on the bench with a brake bleeder pump and a duino. using a 5 volt reference.

inches of mercury, pin value
ambient, 762
3, 667
5, 619
8, 543
10, 493
14, 390


~25.18 units per inch

Map pinout (your sensor may be different)

connector  _________
front     (_________)
              ||
            A  B  C
           +5  -  Signal (on analog 1)

looks pretty linear till you get near ambient. The cheap gauge on the pump probably has a lot to do with that.

int mapPin=1;
void setup(){
  Serial.begin(9600);
}
void loop(){
  Serial.println(analogRead(mapPin));
  delay(500);
}

[cmj]

If you don't mind, I'll be adding my .02 to this thread very soon!

[Daox]

Whatcha thinking about doing with map sensor info dcb?

[Old Tele man]

...a computerized VACUUM gauge path toward realtime BSFC?

[dcb]

looking around it seems like there might be different map sensors in circulation, so folks would probably have to borrow a vacuum gauge and pump to do their own calibrating.

[Old Tele man]

...both of those plots look very linear to my eyes!

...what R-squared values do you get--three-9's or better?

[dcb]

yes linear, but different all the same, you still have to figure out your own personal slope and offset for the map sensor in your car if you are looking for absolute numbers. Of course as a "beat your own high score" semi-arbitrary indicator then it is fine.

[Old Tele man]

...it looks like a "normally aspirated" sensor (blue) vs. a "supercharged" sensor (pink) to my eyes.

...and, both are 'full-scale' max'ed at 5.0Vdc.

[dcb]

feel free to research it It may be that there are only a couple slopes and offsets in practice and that you can make a good guess by taking an engine off reading.

[Old Mechanic]

If you know the MAP, RPM, and fuel consumption, shouldn't you be able to map BSFC for any engine?

regards
Mech