MAP Sensor Voltage to Pressure PLEASE

[Speedy3]

I'm going to build my own circuit to attenuate the output voltage of the MAP Sensor to the ECU. To save me a little work, I was wondering if any of you have logged or measured the MAP Sensor's voltage vs the actual pressure? I just want to get a general idea of the range. Also, does anyone know if the sensor is linear? A spec sheet would help too if anyone happens to have it.

 

[matsuda]

I'm going to build my own circuit to attenuate the output voltage of the MAP Sensor to the ECU. To save me a little work, I was wondering if any of you have logged or measured the MAP Sensor's voltage vs the actual pressure? I just want to get a general idea of the range. Also, does anyone know if the sensor is linear? A spec sheet would help too if anyone happens to have it.

Use this formula:

p = (v / 1.89) * 14.7

p is absolute manifold pressure in PSI
v is MAP voltage
14.7 (PSI) is one atmosphere

For example, a MAP voltage of 3.9V would correspond to a boost pressure of 15.63 PSI.

(3.9 / 1.89) * 14.7 = 30.33 (absolute pressure)
30.33 - 14.7 = 15.63 (conversion of absolute to gage pressure)

The sensor output is linear.


EDIT: MAF changed to MAP, sorry for the confusion!

 

[tru-boost]

it is my undestanding that you cant really find manifold pressure based on just a maf reading. the maf is before the turbo on this car. so a lot of factors come into play.....ambient air temp, boosted airtemp, amount of pressure loss in your system.

 

[Speedy3]

...
For example, a MAF voltage of 3.9V would correspond to a boost pressure of 15.63 PSI....

Did you mean to write "MAP" here?

Wow, thanks a lot! How did you come by this info? From your own measurements?

 

[mrlilguy157]

neil is correct. the air isn't pressurized before the turbo, unless you're using a turbonator!

the MAF CAN determine volumetric airflow though (thats its purpose), as well as the temperature.

 

[Speedy3]

I'm talking MAP, not MAF. Manifold Air Pressure sensor.

 

[tru-boost]

aahhhhh, i swore it said MAF.

 

[Speedy3]

aahhhhh, i swore it said MAF.

Yea, I think he mean't MAP in his answer.

 

[matsuda]

Did you mean to write "MAP" here?

Wow, thanks a lot! How did you come by this info? From your own measurements?

Sorry... I meant to say MAP.

I have measured and seen specs for a lot of MAP sensors. The one in the MS3 is actually rather typical for a 2.5 bar sensor.

 

[Speedy3]

Sorry... I meant to say MAP.

I have measured and seen specs for a lot of MAP sensors. The one in the MS3 is actually rather typical for a 2.5 bar sensor.

Do you know the input resistance (approximate, assuming DC) on the ECU side without the MAP Sensor attached? Also, do you know what kind of sensor the MS3 MAP sensor is? Is it hall effect or resistive or is it an encapsulated circuit?

 

[Shagate]

Do you know the input resistance (approximate, assuming DC) on the ECU side without the MAP Sensor attached? Also, do you know what kind of sensor the MS3 MAP sensor is? Is it hall effect or resistive or is it an encapsulated circuit?

Piezoelectric Element

 

[tru-boost]

according to that equasion i was pretty damn close when i initially set my map clamp. i just did it blasting down the street watching my boost gauge while my buddy held a volt meter !! i was set at 3.9V and we determined that was 16psi.......pretty good for doing it on the fly !! i did still get some cut with that setting though. i dropped my voltage down to 3.25V now, and all is good. that comes out to about 10.6psi using this method....sounds about right. just keeping it below 16psi does not get rid of the cut. the car still thinks 15psi is too much in many cases at higher rpm's.

 

[Speedy3]

Piezoelectric Element

Seems like a strange pick for a MAP sensor considering all the noise induced by vibration. Are you sure it is PE?

 

[funktownp5]

Depends what type of sensor, either 2 or 3 bar. The GM sensor is one of the

easiest sensors to use.

http://hhscott.com/93tmv/3-bar_map.htm

 

[Shagate]

Seems like a strange pick for a MAP sensor considering all the noise induced by vibration. Are you sure it is PE?

Right out of the service manual.
Well, MS6 manual anyhow -- would be the same though.

 

[Speedy3]

Right out of the service manual.
Well, MS6 manual anyhow -- would be the same though.

Ok, thanks all. I should have enough to work with to build this circuit.

 

[Mid_Life_Crisis]

Ok, thanks all. I should have enough to work with to build this circuit.

Did you know there is a how to with a schematic on this site?

 

[Speedy3]

Did you know there is a how to with a schematic on this site?

I looked at some of those and many more on other sites, but they are crap solutions. Don't get me wrong, I'm sure they work fine, but are poor Electronics Engineering.

I'm going to design a much better design that will isolate my circuit from interacting with the sensor and feed an adjustable, attenuated voltage range to the ECU.

I have always liked to figure some things out on my own; I learn much more that way. Besides, I have many years of experience in Electrical/Electronics Engineering and know how to design high quality circuits.