Problem adding MAT to $0D TBI 7427, Not pulling timing.

[96lt4c4]

Part of the reason you get unexpected results is because the code in the 7427 is more complex than the simpler machines like the 747. This complexity increases on an order of magnitude when you get to OBDII and I can promise there are plenty of cases floating around where a newer pcm doesn't do as expected, either.

Sorry for the crickets. You're not the only one left playing with the old pcm's. I just don't have the time that I used to.

CPI trucks use air temp as a compensation. IAT or MAT, it's really no different from the ecm perspective. Sensor generates data, code responds (or doesn't). First, ensure the air temp sensor code is not a current code. ECM will fall back to default temp if there's an error. Then look for minimum temps to enable / disable compensation, or timers that have to expire before compensation begins. Are you certain that the definition file you're using is configured to display timing correctly? Did you notice any performance changes?

My tune is based off of the stock bin that came with the truck. 1994 TBI BJLF $0D. The base timing is set to zero and has been verified at idle with an adjustable timing light. The only initial performance changes I noticed when enabling the MAT was that, the truck fell on its face under boost from going extremely rich due to the MAT & CTS Blend Multiplier vs. Airflow table. I copied the table out of a stock CPI bin. The fix was to just enter all 1's in the table to make the PCM bias ECT instead of MAT. I think this would only have an effect on AFR and not timing, I may be wrong. I plan on looking at this again later, but for right now its working. The truck's VE tables are pretty close and I am getting the AFR I am commanding in the PE AFR table, under WOT, via my wide-band/boost controller.

I am 99% sure the timing I am logging and commanding is what the motor is seeing. I added a degree to the PE timing table, and the log shows 1 degree added to my timing table during PE. The test that I tried with the -10 degrees in the entire MAT Spark Advance Compensation vs. MAP vs. Temperature table did not pull any timing at all anywhere and did not change performance. Thats one of the reasons I used -10, because I knew I would be able to feel it happen but nothing changed. I may start looking back through the hack to see if I can find something that has been missed.

You are right about that code, when I noticed the overly rich condition and suspected the MAT, I unplugged it and the truck ran great, so that may be an old code.

There are the 2 MAT Spark multiplier, Neagtive and Postive, tables. The way I understand these are, there has to be a value in the table for the MAT Spark Advance Compensation vs. MAP vs. Temperature table to work. So if the negative and positive tables are zeroed out, it basically deactivates the MAT Spark Advance Compensation vs. MAP vs. Temperature table. So I have all 1's in from 55 KPA up to 100 KPA. Which in my case is actually 100 KPA up to 200 KPA, 2 BAR MAP for boost. I need to change my .xdf to show this. I have been trying to change tables to show the 2 BAR MAP readings as I come across them, just have not done these yet.