Do you mean that the table does not show similar values?

 

I used to work with Honda ECUs (Assembling/Disassembling Code) and it may be in different locations.

Try to use a Hex Editor to look for those values (in Hex) inside of your ECU *.hex / *.BIN file. I bet that you will find that sequence and find the offset in the EDM file.

Send me the binary and I will try to look for the string in there. Can anyone confirm if the EDM model has a JDM Map Sensor or USDM? Then, I will know what string to look.

email: joed.rodriguez@gmail.com

 

Yes the units are completly different.

I get:
1920 246
65535 246
27064 248
65535 249
27186 251
8 253
25 0
32 2
40 3

fault unit is 4


It is the USDM.

 

Shouldn't 0 volts be -14.7 psi instead of -14.5? Also could you share with us the other data points on the chart you posted? You have 10 dat points on the chart but it is not clear what is the voltage and the psi.

 

A perfect vacuum at sea level would be -14.7 psi. I suppose that would have been the better value to use. The 0.2 psi doesn't matter in the correlation though. It falls well within the estimation error. Without attaching the sensor to a vacuum chamber, I couldn't say within +/- 0.5 psi what pressure actually corresponds to 0 volts.

Which chart do you mean?

 

Nevermind, I figured it out. It was staring me in the face

 

One more question mrfred:

Where did you come up with the number 1.4546 in the JDM formula of V=0.1028p+1.4546? Is that the voltage that you measured @ the altitude that you are at?

The formula comes from the chart that you posted here

https://www.evolutionm.net/forums/sh...3&postcount=23

 

The data points in the plot are data that I acquired with the sensor attached to a pressure manifold that I setup at work. I just did a straight line fit to the data that I acquired. 1.4546 is the y-axis intercept at x = 0. If you are wanting to use the JDM sensor, I'm thinking that you probably want pressure as a function of voltage. Just invert the correlation to get:

P [psig] = 9.73V - 14.14

The correlation based on the 1.334*x used by the ECU would give a P vs V correlation of

P [psig] = 9.87V - 14.7

Take your pick. The correlations are within 0.2 psi of each other at boost values from 18 to 28 psi.

 

Here's a nice table that shows kPa vs altitude:

http://en.wikipedia.org/wiki/Pressure_altitude

Multiply kPa*0.1451 to get psi. Most people are not at sea level, so a more representative offset might be something closer to 14.3 to 14.5 psi. You are in Long Beach, so you could actually use 14.7. :-)

 

The x-axis is psi and the y-axis is volts. So @ 0 psi you got 1.4546 volts. But that is altitude based. When I measured the voltage here in LB on my old 8 I got 0psi=1.6V. So I think the formula @ my altitude should read

V=0.1028p+1.6

Am I correct? Or am I worng?

 

I wouldn't expect atmospheric pressure on an Evo 8 MAP sensor to read the same voltage as the JDM MAP sensor. My location is just 300 ft above sea level. My correlations should be perfect for you.

 

I think I was correct in my assumption about your numbers being altitude based. Today I measured the voltage from the JDM MAP sensor @ the ECU pinout (it is the solid yellow wire on the right most ECU plug when you are looking stright @ the ECU from the passanger side). The voltage was 1.508 @ sea level. So the voltage-to-psi conversion to use if you are logging the JDM MAP with an LM-1/LMA-2/SSI-4 and you are @ sea level should be:

PSI----Volt
-14.7---0
-8.9----0.593
-4.4----1.056
0-------1.508
20.1---3.574
32.7---4.870

I will log with my LM-1/LMA-2 soon and se how the numbers compare to the log from the OBD2 port. I suspect that the LM-1/LMA-2 will give me more data points than the OBD2 port. This is based on my experience when I logged the RPM from the OBD2 and the LMA-2. The OBD2 data was slower than the LMA-2 data.

 

Don't assume at -14.7 psi = 0 volts. Better to just adjust the equation I posted previously. My original equation is:

V = 0.1028*P - 1.4546

If you are measuring 1.508 volts with the ign on and the motor not running, then use:

V = 0.1028*P - 1.508

 

I assumed that 0 psi = 1.508 volts and plugged 1.508 into your equation to get the results. With that -14.7 psi was equal to 0.00316 volts. I followed the same method for all the other psi values.

 

Ah, ok. That's fine.