I just swapped my 88 IROC to a 749 with 2-bar sensor. Everything went relatively well. After copying the VE and timing tables, reducing AE, etc, I've driven the car over 2 hours with very little for problems.

There are two problems I am having that I don't see in searches I've done.

#1: MAT sensor reads 170+ degrees at startup and slowly decreases while running. I've checked my ADS file and the MAT lookup table is consistent with the 6E and posts on this board. The sensor (and byte location in the ADS file) is correct because when I disconnect the sensor, the reading goes to 392F. The pinout on the ECM has been verified mulitple times. Seems like I am getting a good signal, it's just backward. What am I missing?

#2: In my data logs, spark advance with respect to reference pulse is 6* higher than with respect to TDC? This should be the other way. I've checked the physical timing with a light and appears that it follows what the "reference angle" advance shows. Are the byte locations in the ADS file switched? Right now my file show SA with respect to TDC on byte #27 and with respect to reference pulse on byte #25. Can someone verify?

I have done my entire project by merely searching through this board. This is my first brick wall. Any insights or help is appreciated.

Thanks,
Brian

 

1) the MAT lookup table is inverted. Disconnecting the sensor should make it go to -40C (full cold). ADC counts of 255 is -40°C, ADC counts of 0 is 200°C.

2) byte 27 is the final SA w/o the base. This is relative to the reference pulse.

The bytes at 25 & 26 is the SA relative to TDC, it includes the base. However, it does not include knock retard.

RBob.

 

Thanks for the reply, RBob! Your answers to other posts have helped me considerably. Your response brings me to a couple more questions.

I found a flag in $58 for "Inv. MAT option" and am wondering what that's used for? This option is enabled in all of the $58 bins I've read. Does that have anything to do with my inverted MAT table problem?

Also, the $58 ADS file I am using came from the SYTY website. Why would it have an inverted MAT table? Anybody else have the same trouble?

I went back and checked my data logs with the original '165 and the MAT readings are correct. The MAT table in that ADS file is identical to the one in my $58. Why would I need to invert it?

As far as timing, again, the ADS file is directly from the SYTY site. Why are the byte locations for SA switched?

Sorry to keep digging but I need to understand this completely. Thanks again,
Brian

 

That option bit selects between the CTS and MAT for the inverse temperature term for the PW calculation. Has nothing to do with the error in the ADS file.

If the MAT is not being reported correctly, then why can't the lookup table be incorrect? Same with the SA, if what you see and have confirmed to be correct doesn't line up with the ADS data log, then it would seem to me that the ADS file is incorrect.

RBob.