INFO: 3 bar MAPs on Stock LNF base file

[Boxmonkeyracing]

Does anyone have the 3 bar map?

[23547895]

3 Bar

Linear 65.89
Offset -6.35

Be sure to look at engine diag/airflow for any other changes.

[CDNITE]

I would recommend calculating the actual Linear and Offset values of your sensor and not just using the product data values. Actual can be a good bit off and changes over time.

Build a PVC pressure chamber with a calibrated pressure gauge, that you can mount the MAP sensor too. Then use a pump or air compressor to charge the chamber while taking readings from the MAP sensor with DMM.

Here is how to calculate the scalar and offset for a MAP sensor.

1. Find the minimum and maximum voltage and absolute pressures.
2. Convert the pressures to mbar.
3. Subtract the minimum and maximum voltages to find the range, then do the same for the pressures.
4. Divide the pressure range by the voltage range to calculate the scalar.
5. Multiply the minimum voltage by the scalar to calculate the offset. Note that a positive voltage gives a negative offset.

Example for a 3.5 bar MAP sensor:

1. For a 3.5 bar data sheet:
0.5V @ 0 kPa (absolute)
4.5V @ 345 kPa (absolute)

2. 345 kPa = 3450 mbar.

3. Voltage range = 4.0V, pressure range = 3450 mbar.

4. 3450 / 4.0 = 862.5 = scalar

5. 862.5 x 0.5 x -1 = -431.25 = offset

So scalar = 862, offset = -431

Plug in the minimum and maximum voltages to check your work:
0.5V x 862.5 - 431.25 = 0 mbar @ 0.5v
4.5V x 862.5 - 431.25 = 3450 mbar @ 0.5v

If you have trouble then draw a graph and extrapolate the lines until they cross the pressure axis.

I can make a How to if there is enough interest.

--Christian

[cobaltssoverbooster]

y=mx+b
b= 0v pressure offset int kpa
m= slope = (Y2 -Y1)/ (X2 -X1)

record 2 pressures. i always record one at atm so no pressure or vacuum applied and the second closer to the max voltage range of the sensor.
so slope is: (high pressure voltage - atm voltage) / (high pressure kpa - atm kpa)

pick one recorded plot and plug it into the formula with your new found M value and solve to find B.
if your not so good at math that comes to this formula:
b= y - (mx)

if you wanted to get fancy you could record 10 or so data plots and use linear regression to find a better fitting line. if your using two points then the further away they are from each other the better.

[CDNITE]

y=mx+b
b= 0v pressure offset int kpa
m= slope = (Y2 -Y1)/ (X2 -X1)

record 2 pressures. i always record one at atm so no pressure or vacuum applied and the second closer to the max voltage range of the sensor.
so slope is: (high pressure voltage - atm voltage) / (high pressure kpa - atm kpa)

pick one recorded plot and plug it into the formula with your new found M value and solve to find B.
if your not so good at math that comes to this formula:
b= y - (mx)

if you wanted to get fancy you could record 10 or so data plots and use linear regression to find a better fitting line. if your using two points then the further away they are from each other the better.

Thanks for adding to my post I should have included the formulas.

The delta in precision decreases with more points, but using 10 would also show you if the slope is linear or if there are areas of over or under performance. I use a spreadsheet and enter the data in the table and have it plot a graph. I've see most sensors lose accuracy above 80% of its maximum range and are not consistent under 15% of there range. But this inconsistency in minor.

I'm starting to make jigs/test boxes to calibrate as many sensor as I can.

--Christian