Newbie question regarding Red/Blue PCMs

[57 Handyman]

One would think that GM would not design separate pieces of hardware to accommodate the various makes, models, and engine/transmission configurations. In the absence of an authoritative/definitive response from someone, and once I get more comfortable with and know what I am doing with these PCMs, I will perform a test to validate or invalidate my hypothesis regarding common PCM hardware.

[buddrow]

To somewhat answer your question, they are different beasts in a few ways. First the 8625 will run the TBI engine just fine, with 2 injectors, blah blah blah. The 5925 is meant to run the CPFI(spider injector) style of multi-port injection. Is the wiring at the red/blue connectors different between the two, you betcha! Stick to the pcm that "came with" the engine you are trying to run. The 5925 likely will never start your engine in its current state.. HTH

Buddrow

[57 Handyman]

buddrow, thanks for providing input to this thread. So, based on what you are saying, the 5925's red/blue connectors will NOT fire the 2 TBI injectors because the BCC (which includes the .bin, .xdf, and . adx are different plus the red/blue connectors are wired differently. Interesting...

With regard to your recommendation of sticking with the PCM my engine came with, all my research/readings online say that it is possible and likely worth the effort to upgrade to the 50x's faster 8625 PCM rather than stick with the slower 4288 ECM that came stock in my '92 4.3L S10.

[buddrow]

It's not so much the connectors themselves as the hardware internal to the pcm as well as the software that runs everything is different.

The '4288 is a direct replacement for the '7747, provided they are both from the same engine size, 4.3,5.0,5.7... The '7747 may not be the best choice for performance applications, but for simplicity, it would be an easier swap than the 8625 since it's a direct swap, no pin swapping. I know this because I have done such a swap in a friends '92 with the '288. The 8625 will run the 4.3L, you will just have to do some pin swapping at the pcm connector. There are wiring diagrams available on this site, or if necessary I may be able to provide you with wiring diagrams for both pcms.

The BCC(broadcast code) is the calibration code name/designation.
the .bin is the actual calibration file
the. xdf is used by tunerpro to organize the .bin file for human viewing, modification, etc.
the .adx is solely for datastream interfacing, datalogging, etc.

These are all different from one pcm to the next, but are the same between different calibrations/.bins of the same pcm number, if that makes sense.
Just food for thought.

Buddrow

[57 Handyman]

Buddrow,

Thanks for your offer to assist me with tuning/reprogramming the 4.3L in my '92 S-10. If the 7747 is a direct swap to my stock 4288, are there benefits to making the swap? Is the internal processor speed higher or the same 160 baud in the 4288?

I am aware of the repining required in switching from the black 4288 connectors to the red/blue for the 8625. I guess my preference for the 8625 is tied to the benefits I've read about on the site and, more so, the amount of work others have already done with the 8625. While I have seen and found a few wiring diagrams, I would appreciate seeing a listing which you have used with success and what your recommendations you'd make regarding sensors, such as O2 and knock sensors. Both of these are the stock pieces and I was wondering if I should be using different ones.

Again, thank you for helping.

[buddrow]

The main benefit to swapping to a 7747 over 8625 is plug-and-play. The 7747 doesnt require any modifcations to the connectors or anything else, its a direct replacement. The 288 has limited support versus the 7747(which is very heavily supported on this site) in regards to xdf, adx, bins, etc. The 7747 is inferior to the 8625 in a couple of ways depending on your perception of things. The 7747 is 160 baud(yuck) vs 8625 which is 8192(9600)baud, this is only noticeable during datalogging/data aquisition though. The 8625 has higher resolution fuel and spark tables which is a benefit, but not a ncessity in my opinion. Ive been running a modded 7747 in my 90 Chevy and to the unaware, you couldnt tell the fuel and spark maps stop at 3600rpm. When it comes to tuning these ecms/pcms, hardware required to do so comes into play. How are your soldering skills as some are required to make updating the bin possible. Time for coffee...:-)

Buddrow

[57 Handyman]

Buddrow,

You've just about got me convinced regarding pros and cons for switching to a 7747. I'm re-evaluating my needs in light of what I've experienced in getting my truck to run smoothly and dependably. At present, it maybe a whole bunch of problems, i.e., vac leak, possible sensor, need to rebuild the TBI again, fuel relay/pump, etc. on top of the internal engine mods I've made...marine cam, .020-in overbore, higher compression--flat-top pistons, 96 Vortec heads, etc. Also, since I wanted to keep the TBI (vs change to a carb), some of these mods resulted in no EGR--the Edelbrock 2114 intake does not have a place for one. Is yours a 4.3L or V8 in your '90 Chevy?

As for soldering skills, I'll be able to do the ones described on this as well as other sites. Now, I also need to find a 7747.