Breaking new ground - 1228747 ECM

I am relatively new to TBI tuning and have been doing some trial and error programming with my 1228747 ECM. I am fighting a surging deceleration right now, but there are limited IAC-related scalar values dealing with DFCO available to modify in the current 1228747 xdf. I was looking through the current 7747 xdf and there are a lot more values available to modify, so I thought why can't they also work for 8747? Using the current 7747 and 8747 xdfs, a few stock 5.7L manual transmission bins (mostly because its similar to what I am running), and Mark's post on 7747 IAC Operation (http://www.gearhead-efi.com/Fuel-Inj...pdated-12-4-00) I started copying over IAC scalars and readdressing to match the 8747 bin. I found a 20 byte address offset between 7747 and 8747 bins (8747 shifted down 20 bytes for some reason?) requiring all of the byte addressing to change. I started at the top and worked my way down and most everything matches up (see attached spreadsheet), but there are a few that I highlighted that weren't quite right. Is there other documentation somewhere with all of this addressing, either for the 8747 or 7747? Because these two ECM's are so similar, is this even possible and just hasn't been done yet or am I chasing my tail? Would you guys look over this new xdf and see if I'm on the right track? I would really like to update the 8747 xdf to include as much information as the 7747 does.

I got looking into these $4F Hac files and wondered what they were. I hoped the AKWH_HAC.SRC file in Notepad (AKWH was the stock BCC for my truck) and WHOA!!! There is the parameter address map I was looking for! Looks like I will be spending a lot of time creating and addressing these new parameters into the xdf! :rockon:

Chewy1576,

Where did you learn to do all of the steps required to do the re-programming for your 8747? Specifically, I am interested in learning about the tuning process. Like you, I am in the process of breaking new ground and learning how to tune.

I have read and re-read a bunch of threads on this site and others but without some basic familiarity and knowledge, most of what I read is gibberish. As an old guy venturing into this EFI tuning world, I need a recipe and instructions. Currently, my project is a resto-mod of a '92 4x4 S10 and involves upgrading to a 8625 PCM. The 4.3L has been slightly modified and thus requires tuning to optimize performance. These V6 motors are not the beast like your 383 and so optimizing performance thru tuning is critical if one does not want nor have a bunch of dollars to spend.

Look forward to following this thread and learn.

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Originally Posted by 57 Handyman

Chewy1576,

Where did you learn to do all of the steps required to do the re-programming for your 8747? Specifically, I am interested in learning about the tuning process. Like you, I am in the process of breaking new ground and learning how to tune.

I have read and re-read a bunch of threads on this site and others but without some basic familiarity and knowledge, most of what I read is gibberish. As an old guy venturing into this EFI tuning world, I need a recipe and instructions. Currently, my project is a resto-mod of a '92 4x4 S10 and involves upgrading to a 8625 PCM. The 4.3L has been slightly modified and thus requires tuning to optimize performance. These V6 motors are not the beast like your 383 and so optimizing performance thru tuning is critical if one does not want nor have a bunch of dollars to spend.

Look forward to following this thread and learn.

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I only started with DIY tuning about a month ago. I have read a lot of the threads on this forum to try to get an understanding about what to look at and what everything means. My biggest accomplishment so far is running my 383 using a SBC throttle body and BBC injectors (80#/hr). There are a lot of threads around from Mark and Dave that give some really good instructions and tips for tuning. Dave has made some spreadsheets too that make tuning the VE tables no more difficult than data log, copy, paste, copy, paste, and burn. After a few cycles of doing that, the fueling is pretty close to where it needs to be.

The research I'm doing for this thread applies specifically to the 1228747 ECM. While it is almost identical to the 1227747 ECM, they are still different enough that the '7747 tools don't work with the '8747. There are still tools available for tuning the '8747, but I'm hoping to open the '8747 to the same level of customization that the '7747 is at.