Throwing out a PCM idea... - Page 3 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 10-30-2007, 07:53 PM   #21
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I am looking at the 96 and 97 PCM pinouts, just to see if there are any differences. After skimming, I found that one difference is that the '97 PCM has a direct input from the fuel tank sender, the '96 appears that it doesn't. There are also fuel tank pressure inputs as well, but I think those are Buick-specific. Me thinks this is gonna be alot of work....a whole lotta comparisons between old and new.

First plan of attack is to map out all the differences between the 96 and 97 codes, inputs, etc. Choose the one that requires the least amount of additional sensors, then compare that one to the 93 (which I know requires less sensors). Whatever cavities are left on the new PCM are the sensors that will need to be added to the car, or deleted from the programing.

Eh, it'* a start.
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Old 10-30-2007, 08:09 PM   #22
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Quote:
Originally Posted by sandrock
I am looking at the 96 and 97 PCM pinouts, just to see if there are any differences. After skimming, I found that one difference is that the '97 PCM has a direct input from the fuel tank sender, the '96 appears that it doesn't. There are also fuel tank pressure inputs as well, but I think those are Buick-specific. Me thinks this is gonna be alot of work....a whole lotta comparisons between old and new.

First plan of attack is to map out all the differences between the 96 and 97 codes, inputs, etc. Choose the one that requires the least amount of additional sensors, then compare that one to the 93 (which I know requires less sensors). Whatever cavities are left on the new PCM are the sensors that will need to be added to the car, or deleted from the programing.

Eh, it'* a start.
That direct fuel tank sender input on the '97 doesn't matter. I never did any wiring for it during my swap and the fuel gauge, idiot light and everything else works just fine. As for the fuel tank pressure sensors, those are only on the Vin K cars so that doesn't matter either.

Other than those two differences and the pinouts for the trans, the '96 and '97 PCMs are identical from what I can remember.
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Old 10-30-2007, 08:24 PM   #23
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I'm seeing that now that I put the pinouts side-by-side. Next step - compare pinouts to the '93.

Fun.
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Old 10-30-2007, 08:44 PM   #24
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Well Brad,

I've offered up my opinion to you directly, but I figured I would voice them again here just so the others can consider the merits of them.

I'm not a big fan of the DIY efi controller. Yes, it has a marketable name, but it is still a home brew and if you choose to implement it, you are pretty much flying solo. You must come up with a reasonable set of calibration data just to get the sucker to start. Then you are doing the same things you would have to do with Tuner Cat and the stock PCM.

Yes, as pointed out, TunerCat is not exactly "user friendly". But, NONE of the programmers are user friendly either. The good news is that they all work the same way, since they all have to work with the same suite of sensors and drive the same devices. (In other words..once you get over the first hurdle of what all those numbers mean, you pretty much have conquered all controllers.)

Of all the ECM'* I've worked with, the GM models work as well as the rest, once you get some software to decode the EPROM and learn what you can change...and what you should leave alone.

Last, I don't think you are going to be too far off the mark just using the stock ECM. Jinx runs on it now. While it needs some refinement (and some data collection to figure out what needs changed and where) it still a major leap forward to have the car running and capable of holding an idle. In the realm of tuning cars & bikes, just getting the sucker to idle is often a challenge when starting from scratch. With any other ECM, You must recreate what GM already did for you with the stock calibration..get a starting point to work from.

I hope that makes sense. I'm not trashing MegaSquirt, Haltech, Accel, Holley, or any other ECM system. They all work pretty much the same way, so why not stick with a winner...(i.e. the GM one you have in hand)

I'll use the same line I give my user'* in the IT world..."there'* no magic inside the box"
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Old 10-30-2007, 09:10 PM   #25
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Ah, Mr. Curt finally stumbled onto the thread

Actually, it was that very conversation that led me to think about this very modification. As much as I would like to have done MS, the lack of a trans controller negated it. So, for us, a GM PCM is in reality the only way to go.

After speaking with Don, he is really excited about doing the OBD2 swap, as am I. The tuneability is there, processor speed is there, and the diagnostics are better than what is running the car now. Granted, Jinx runs, and runs reasonably well with the mods I have. But...it *could* be better.

The thing is, nobody can really tell if this is a bad idea or not...it'* never been tried. I can safely say that it would be a better alternative to any stand-alone system offered right now...cost-wise, it'* much cheaper, PLUS it can control the trans.

So, in effect, I WOULD be using a GM PCM...just not the factory installed one
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Old 10-30-2007, 09:39 PM   #26
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Quote:
Originally Posted by sandrock
The thing is, nobody can really tell if this is a bad idea or not...it'* never been tried.
Yep, so long as you don't hit any roadblocks (little things used to get in the way of updating ECM'*...like VATS on a car that never had VATS, or a sensor you have no way of recreating/emulating/faking out.) Otherwise, the basics of engine management still apply..as you have already seen, there'* a great deal of common wiring when it comes to the engine harness. (I've even run a V8 TPI motor off a V6 MPFI ECM...most of the sensors are the same from cars of the same make...yeah, it ran like **&^ but it did run! )

I would be inclined to stick with the ECM your car is already wired for, just for the sake of simplicity. I doubt you really need the extra features the OBD-II pcm will give you. Yes, the procs got faster, the memory got larger, and more bells and whistles got tacked on with OBD-II...but the motor never really "needed" them. And in some respects, the added complexity can work against you.

Personally, I would learn from what you have, tinker with it, and then decide if it can't hack the job. The time and effort spent now will go a long way towards understanding what the ECM is capable of.

If you think your stock ECM is a dinosour, take a look at some of the ones from the 1980'* that ran the TBI motors reasonably well...they are like pocket calculators compared to the stock one in your car now...and amazingly enough, they still work well for a lot of application (hint, they are the basis of the Accel and Holley aftermarket ECM'* )
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Old 10-30-2007, 11:01 PM   #27
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Quote:
Originally Posted by sandrock
The tuneability is there, processor speed is there, and the diagnostics are better than what is running the car now. Granted, Jinx runs, and runs reasonably well with the mods I have. But...it *could* be better.

The thing is, nobody can really tell if this is a bad idea or not...it'* never been tried. I can safely say that it would be a better alternative to any stand-alone system offered right now...cost-wise, it'* much cheaper, PLUS it can control the trans.
Let'* take your logic a step at a time:

TUNEABILITY:
Yup. Can't deny that with a DHP Power Tuner (your only option). The question is why? Is there some reason you need this ability?

DIAGNOSTICS:
Better? No. Not really. 4 digit codes vs. 2-digit codes? They tell you the same thing with different numbers. Can you name an OBDII parameter that really matters that OBD1 doesn't provide?

PROCESSOR SPEED:
Is that even a factor? Do you have evidence that it matters? Has the stock OBD1 PCM processor speed been shown to be lacking? What would you gain from faster processor speed?

YOU'D BE THE FIRST:
You'd be the first to try something that may not benefit you based on the above points. Is it worth the cost and trouble, plus the cost of the tuner?

These are the questions you have to ask yourself, and answer for yourself. It'* your car, your money, and your labor. Is the idea worth any of those?

From my experience with the OBD1 L67'*, I'd maybe think of this option in another year or two down the road on the Zilla only.
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