MAP sensor data

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Aug 24, 2005 | 12:35 PM

Dirty Dave

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Junior Member

Joined: Jul 2001

Posts: 38

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From: Edgewood, MD

Car: 85 Berlinetta

Engine: sort of working

Transmission: B&M 700R4

MAP sensor data

I posted this originally on the Tech board here in response to a question I had about some weird MAP data I was getting. I think the info is more useful on the carb board and maybe others with more experience may have more to say about it:

What I did was measure what the computer was reading vs. actual input vacuum with a hand pump and gauge. Here's what I came up with:

Code:

Input Vacuum ("Hg)           MAP reading (kPa)
------------------------     ----------------------
          0                             21.4
          5                             36
         10                             53
         15                             70.2
         20                             87.4
         25                             103.2

Indeed this seems to be a direct vacuum sensor! The curve fit of this data is extrememly close to the following equation which allows for exact conversion of the "MAP" reading in kPa to "Hg so you can have real-time manifold vacuum data like any other true MAP sensor:

Manifold Vacuum ("Hg)= (29.92/101.3)*kPa - (29.92/101.3)*20

or in simpler terms:

Man Vac "Hg = 0.295*kPa - 5.91

This actually matches my data well at idle of 76 kPa which converts to 16.5 "Hg!

I just hope this is the type of sensor the ZZ4 computer needs to see data from. I compared 2 "MAP" sensors from CCC quad cars and the output is virtually identical to what I found, so I'm taking that as a good sign.

Also, even though my car has a BARO sensor and all the proper wiring for it going to the computer, the computer either ignores it or only takes 1 reading right at key on because with the power on I varied the input vacuum on it too but the output didn't change.

I hope this is useful info to someone besides me