What's Your Opinion

[Hard Driver]

My vehicle is an 87 S blazer[stock engine was 2.8]with a 3.4 crate engine,engine came with a mild 260 upgrade cam and I added a larger 4.3 tbi and freeflow catback.I had picked up a 7427 ecm but after some reseach I feel that the stock ecm w/chip would probably handle the needed tuning for these mild mods.I can save the 7427 ecm [5.7] for another project or mostly likely sell it.What is your opinion ?

[gregs78cam]

If it were bone stock then I would say keep the stock ECM. If you think you're going to spend some time tuning it, and the stock ECM is a 160 baud, then I would upgrade it, there is no reason not to. Tuning is much easier with a faster PCM. Such as, you can see transient conditions easier i.e. lean spikes or bogs, and BLM datapoints fill in much quicker with more samples. Also there are MANY more items to monitor in the datastream for troubleshooting and tuning.

[Hard Driver]

It appears that I may have to scrounge the connectors for the 7427 and rewire to fit,I thought that if the stock ecm could be tuned to handle the engine requirements it would simplify things .

[PJG1173]

I run the 8625 in my S10 which is the MY before the 7427. I like it and have had no problems tuning it, at least none that couldn't be solved by other members here. IMHO its well worth the upgrade.

[Hard Driver]

I run the 8625 in my S10 which is the MY before the 7427. I like it and have had no problems tuning it, at least none that couldn't be solved by other members here. IMHO its well worth the upgrade.
So you are running the 8625,which appears to be for a 4.3 and it allows you to tune correctly? I know from reading the the 7427 is the more "tuneable" ecm but I don't relish the idea of scrounging the yards looking for the right connectors and splicing them into the existing harness if a tuned stock ecm will serve my needs.

[PJG1173]

So you are running the 8625,which appears to be for a 4.3 and it allows you to tune correctly? I know from reading the the 7427 is the more "tuneable" ecm but I don't relish the idea of scrounging the yards looking for the right connectors and splicing them into the existing harness if a tuned stock ecm will serve my needs.
I upgraded to the $0D mask a while back with a bin from a 7427. the good thing about these PCM's is the abundance of tuning support in the community. Not sure which ecu you have stock but I doubt it has the same amount of support as this one does. I'm getting ready to do an EFI conversion on my toyota and I'll be using another 8625 wasn't too hard to find the wire connectors in a JY. all 93-94 S10's and astro vans, or 93~95 full size with the 4l60e will have what you are looking for. watch out for the 95 s10's sometimes they have the wierd ODB1.5.

[Hard Driver]

OK,if the connectors are that easy to find I'll grab em next time at the yard.

[RobertISaar]

personally, i'd never touch an ECM that outputs anything less than 8192.

to that effect, the EBL would work to get around that. Dimented24x7 also released a patch that made one of the old TBI ECMs comm at 38,400 baud.

[EagleMark]

Dimented24x7 also released a patch that made one of the old TBI ECMs comm at 38,400 baud.Man that is fast! Wonder how long the old ECM could keep up though without having a heart attack/overheat/smoke and fire? Would be like overclocking a PC CPU but need extra cooling!

Yeah you could tune with the old ECM, been done many times. But even then same engine with upgrade to newer PCM is better and it's not that hard to repin and change a few wires from knock/ESC module because newer PCM has knock module in memcal. Since your a V6 getting the right memcal to start with should be easy as well at JY while getting PCM plugs.

[RobertISaar]

the '8063 as used in TBI F-bodies running $4D.

quite a few upgrades to the code... and technically it's not a patch, it's the ASM of the entire calibration/algorithm section. could be run through an assembler and sorted out to make the 4KB BIN though.

[Hard Driver]

Ok,it seems I jumped the gun by buying the 7427 / 5.7 engine,no problem I a can probably sell it and get my money back.Since I need the connectors I can get another but is the one from a 4.3 better ? I read one post that said one from a 305 [drop two cyls] was better because it would be closer to the same bore as a 3.4 engine.

[PJG1173]

if the memcals are interchangeable between 7427 and 8625. I have a 4.3 memcal I'll trade you for your v8 one.

[Hard Driver]

if the memcals are interchangeable between 7427 and 8625. I have a 4.3 memcal I'll trade you for your v8 one.I'll have to research that, I have no idea,maybe some one will enlighten us.

[PJG1173]

I'll have to research that, I have no idea,maybe some one will enlighten us.
I'm sure someone will.

[93V8S10]

They will interchange, the 7427 and 8625 are nearly the same thing.

[Hard Driver]

They will interchange, the 7427 and 8625 are nearly the same thing.
Anyone concur,will the memcals interchange and what's the difference between the 7427 / 8625 ?

[EagleMark]

He's the expert so I will concur. 7427 was the last year for that series of PCMs. 7427 will run any mask $0D, $0E, $31, $E6 or tranny, others may have issues with 4L80e, they will all run 4L60e, 700r4, non e auto or manual trans. Very versatile PCM.

[Hard Driver]

In the interest of learning,why is it better to start with a 4.3 memcal vs the 5.7 when tuning for a 3.4 engine,does it make tuning easier ? Please explain in layman's terms if possible.

[RobertISaar]

cylinder select on the 2 little chips that are under the knock filter would be my guess.

[Hard Driver]

OK,Thanks. It was suggested on another forum that when using the 7427 to use for a 3.4 engine get one from a 4.3,another suggestion was get one from a 305 because the cyl bore size was closer to the 3.4's bore.

[EagleMark]

You can tune a piano but you can't tunafish!

In other words you can tune the chip and you will have to tune the chip. But you can not tune the netres/limp home chip below knock sensor so it would be better to start with a six cylinder Memcal then an eight cylinder memcal. Or modify the memcal but no reason to when you can swap for one. Then when starting the bin use a six cylinder bin and make the cylinder volume, injector size etc... adjustments to get a close start for tuning.

Three parts in a memcal. Chip, limp home chip and knock module. Six cylinder memcal is way better starting point.

Knock module is also in memcal so that is going to be an experiment as the 4.3L knock sensor is a match for knock module, but a 3.4L knock sensor may work better? Have to look into that...

[Hard Driver]

Thanks,that makes things much clearer,gaining knowledge a post at a time !