Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

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- Instrumentation (https://ecomodder.com/forum/instrumentation.html)

- - Reading a MAP sensor (https://ecomodder.com/forum/showthread.php/reading-map-sensor-5208.html)

dcb	09-22-2008 09:24 PM

Reading a MAP sensor

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)

Code:

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.

Code:

int mapPin=1;

void setup(){

  Serial.begin(9600);

}

void loop(){

  Serial.println(analogRead(mapPin));

  delay(500);

}

cmj	09-17-2010 10:12 PM

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

Daox	09-18-2010 12:58 PM

Whatcha thinking about doing with map sensor info dcb?

gone-ot

09-18-2010 03:00 PM

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

dcb	09-18-2010 09:49 PM

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.

http://img.photobucket.com/albums/v6...ltagetable.jpg

gone-ot

09-19-2010 05:13 PM

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

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

dcb	09-19-2010 05:27 PM

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.

gone-ot

09-19-2010 07:29 PM

...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	09-19-2010 07:44 PM

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.

user removed

09-19-2010 09:22 PM

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

regards
Mech

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