I found this graph for the GM 2 and 3 bar map sensors and I calculated a Scale of 6300 and Offset of 800 for the 3 bar (Black Box DL). Note that they are using relative pressure instead of absolute!!

USE AT YOUR OWN RISK!

 

Read my section in the notes about calibration of your map sensor to your PFC/DL.

 

i did

 

First of all, i have the black box datalogit with universal PFC, so it uses the later style numbering for MAP sensor calibration. I have a couple questions then about GM MAP sensor calibration and how to configure the values for my P rows. I do have the tuning notes but I'm trying to apply this to my situation.

I just loaded the Banzai map for my s4 T2. It is supposed to be pre calibrated for the GM sensor I have installed. It is currently set for a scale of 6630 and an offset of 0. I also plan on running around 20-21 psi of boost, so I feel I need to change the values of my P rows.

I was considering changing the P rows:


new original
P17 8250 18000
P18 20500 20000
P19 22750 22000
P20 25000 24000


and then possibly changing the PIM scale to what was just posted at the top of this thread? Or am I going about this the wrong way? And the ultimate question is, how important is it really to calibrate the sensor in the way you talked about in your tuning notes? And how does this calibration relate to the P rows for a high boost application?

 

The PFC calculates absolute pressure in kg/m2 directly from the PIM sensor voltage. The calculation is:

PIM = scale * PIMV + offset

The PFC displays gauge pressure in kg/cm2, which is calculated in the usual way by subtracting standard atmospheric pressure (10332 kg/cm2) from absolute pressure and scaling:

Gauge pressure = (PIM - 10332)/1000

Gauge pressure is what the Commander displays as boost, and is also what the Datalogit logs in its boost column, though inexplicably multiplied by 100.

To calibrate a map sensor one needs to determine both scale (how the sensor reacts to pressure change (measured in kg/m2/V)) and offset (the number required to zero the gauge at local atmospheric pressure, measured in kg/m2).

Assuming linear response away from the edges of the PIM sensor's range, scale can be calculated by taking two non-edge voltage values 1 volt apart (say, 2 and 3 volts) and subtracting the two PIM values corresponding to those values. Offset is simply the number required to zero the gauge at local atmospheric pressure.