GM PCM calibration modules

[rjdrew1986]

I would love to hear others thoughts & wisdom on this topic.

It's my understanding that tuning GM controllers is limited to what is available within the GM calibration modules for tuning each controller. I have (1) point and (1) question on this topic.

1. Point on the number of calibration modules and each modules content. This is a mystery to me. I think the best place to enter this discussion is to reference the P04. From a more 'user' perspective, I particularly like the P04 because so many items were made available to be tuned or calibrated. My gosh, just cranking alone, we can tune pulse widths based upon coolant temperature and which crank reference pulse. I know the P04 is not well liked by many but for what was made available to be tuned, it has been wonderful for me. Conversely. the P08 & P11, sparse few items are available. I (& I assume others) find this very frustrating. There is just enough in the P08 & P11 that I can just get by with the areas that I desire to tune. For one example (but there are many other examples), there is nothing for cranking. However, I do have indirect exposure by going to the VE idle (0% throttle) table and changing the VE values in the 80-100 Kpa range at below 1000 RPMs which effectively is only relevant during cranking to help lean or richen the cranking fuel pulse volume. It works but its not near as beneficial as what's available in the P04. It seems to be generally assumed that for every GM controller there were different internal engineering teams or perhaps different third party vendors with unique views as to what should or should not be included in the calibration modules.

2. Question, is it not feasible to include areas outside the allocated calibration modules for tuning changes? Certainly ProfessWRX has shared several examples where he has had some good successes with working outside the allocated calibration modules for changing/adding functionality. But could working outside of the allocated calibration modules ever become part of routine tuning updates?

[antus]

1) there are 2 angles to this. First is what the PCM was actually designed for, and what is in software and what is in hardware. The hardware and operating systems did evolve and change over time, and the possibilities genuinely did change, somewhat. The second is, what is available is what is known about the operating system and mapped. Just because you don't see it now, does not mean it is not there. There was a lot of work done on the P04 back in the early 2000s as one of the first widely available GM OBD2 V6 PCMs, and they were really well defined around that point in time. Once things are known people can inspect the changes made by prior generations of software to identify the calibration items and map them out in newer generations. Because P08 and P11 are not popular tuner PCMs (yet?) there are likely more calibration items that could be found and added to tools like Universal Patcher with more work. The P04 is so well defined from the work done by the people behind tinytuner, and the database was released freely and is credited in universal patcher as:

Universal Patcher's copy of the Tiny Tuner readme/license includes:

This software, source code, database, and all related files are yours to use without limitation. I do not express or imply any warrenty of any kind, this is yours to use at your own risk.

This program is the result of many hours sitting in front of a computer looking for tables and such to improve our tuning ability. I could not have done this without the help of RedfireGTP, blemke (Bill), Perforator, and Zalfrin. Be sure to thank them as well if you decided to use this program and feel it's worth the time it took to develop it.

- GTPAddict (Eddie)

Also note the P04 does not have the concept of tune partitioning. They just have one giant checksum covering the whole lot. So it is not modular like you describe. That is one of the reasons they are harder to work with. GM improved this over following generations. Other challenges are the CPU bugs in the early 68k core which they use and there are other issues too.

2) You can, so long as the checksum can be calibrated. Most of ProfessWRX's are code patches in the operating system. Operating systems sometimes span areas before and after the calibration. In this case the tool that generates the checksum needs to be able to account for this. Universal patcher can do it. Tunerpro can't, at least not out of the box. The checksum plugins create custom calculators. They really do standard sums, but they know what areas to skip. So the XDF can say the OS sum is from here to here and its a Pxx type (depending on PCM) and so be configured to use a plugin that will sum the right multi-part region by skipping over the calibration part. When you have that setup and working properly in tunerpro you can patch the OS and values that exist in code space (as opposed to the calibration area), or you can do that any time in Universal Patcher.

[rjdrew1986]

Thanks Antus, helpful information.