Whats in the ECM and whats in the programmable chip?

[PPPPPP42]

Ah ok thanks, if the netres is only programmed with a cylinder count that's what I wanted to know for swapping it into anything and everything. I'd be curious to read exactly how a pack of resistors telling the system how many cylinders it has allows the ECM enough info to limp home on a variety of engines.
Is there a reference guide for part numbers for the netres or do you just have to know what the ECM came out of by looking up the 4 letter code for the main chip if nothing else?
Also when I try to research the netres I see them called a calpac instead, am I getting my parts confused? According to that PDF I linked they all have an 8 digit part number when they are the seperate little chip like I think I have.

I knew the memcal was for the later stuff (92 with automatic and 93-95 with auto or manual for obd1 right?) though I got a little rambly and confusing. I was just commenting on the fact that it appears the 2 separate chips got combined into one big one on the memcal stuff from what I was reading.

EDIT: It seems that calpac (or pak) and netres are interchangable terms but if you want to order one from GM you are getting a calpac.
I also found out that:
"16060836 is the (V8) one.
16060837 is the number of the chip without the plastic carrier and IIRC its a GM internal number."

[EagleMark]

Have you ever watched the Big Bang Theory? Sheldon...

You'll have fun here other more knowledgable electronics guys. I'm more a car guy who learns as little as possible of electronics funtions, just what I need to make a car run... but I'll answer some.

It's really not a big issue, I have never needeed it to limp home and I've been driving these systems since 1988. I've done a lot of conversions and just stick V6 or V8 chip in... and never use it. Goal here is never need it!

1. Yes
2. Yes
3. I've seen heavily modiifed engines run on LHM. Not well but run, even stock does not run well but better, rich and not much timing or power. Safe but runs. Never intrested me how or why? I just fix the system so it runs correctly!

Memcals are more complex. There's some good threads around here on them. But not for the LH funtion, more run functions like cylinder count. It also has the knock module/ESC. One PCM covers more vehicles with a Memcal change.

No Etrans with these ECM so no trans funtions. TCC won't work in LHM, but I doubt you could drive that fast? There is a trans LH routine in etrans Memcal PCMs. But I don't recall it being part of Netres/Calpak.

The Calpak statement about gear ratios is not correct for these ECM/PCMs.There is a DRAC or VSSB that handles the gear ratio, speedometer signal from the VSS on the GM OBDI systems. Yes GM calls the little chip Calpak, people have called it Netres and some LH chip.

[PPPPPP42]

Funny you should say that, very not the first time I have been asked if I watch big bang theory (I have seen one or two) and been accused of being Sheldon.

I figured the gear ratio in any part of ECM statement was wrong as I just ordered a 7 pin dip switch (in quantity) to convert my drac so I can use the junkyard dirt cheap 3.73 gear axles I have (current is 3.42).

It makes sense that the older computers don't include transmission stuff in their limp home since they didn't change the ECM to a memcal type until the autos in 92 because of the need for the extra transmission controls among other things I'm sure (thanks for that year/application fact in another thread btw).

Eventually maybe I will tackle some GM engineer and get him to explain to me what the resistors do. Fake sensor data? Act as switches for preinstalled stuff in the computer? If its the second I would imagine they use the same set for different cylinder counts in all ECM's and its the stuff in the ECM it switches that changes.

I will also start looking at calpak numbers to see if there is really only one for each cylinder count or each ecm or what. I will look up the 4 and 6 cylinder calpak numbers for at least the 7747 (was this used in a 4 cyl?) later just to have them I think.

I mainly worry about the calpak being correct because many individual part failures will make it suddenly quite critical to getting home and I hate being stranded.

Most people do just want to learn how to make things work how they want without bothering with all the extra theory and details. It may seem stupid to want to know this much in depth, but if I know exactly what everything in the system does I can more easily learn tuning and diagnostics and predict what things will do. That's how I learned EFI in the first place, I just learned exactly what every part did and suddenly its super easy to diagnose EFI because I know which pieces are doing what jobs and I can rule stuff out based on symptoms and tests.
I also like to know in each type of ECM, what functions are in the ECM, calpak and prom.

There is a site out there where someone as messed up as I am was working to reverse engineer the calpaks to figure them out and even had the help of Moates, but I get the impression they gave up on it from what was on the site. He determined that building a custom one would be impossible since there is really no programming and any other type of resistor pack would be huge, not just a simple change like in the drac. He never did explain exactly how the resistors do what they do though.

[1project2many]

Limp mode is fuel only, no timing control. The NETwork of RESistors in the LHM chip is a simple analog calibration relating injector pulse to various input signals including coolant temp, voltage, MAP or TPS, and rpm. LHM can be duplicated and I know of at least one person who is having netres' made to include with remanufactured 2.5 liter engines supplied to the US Postal Service.

You will find that knowing too many details too soon will lead to a more complicated tuning process. Dropped in NYC with the goal of arriving at a specific destination, can you say the job is made easier or faster if you dedicate yourself to completely learning the subway routes, and street maps, and air traffic routes, and bus schedules, and "on call" service routes? You might make a helluva dispatcher when you're done but really, all that info to replace a simple set of directions? Or asked in another way, do you need to know how digestion works to enjoy a great meal?

GM did away with the redundant fuel devices in the '90s. The ecms are actually very reliable.

[romac55]

BUT , like Mark said ; once the smoke comes out , there's no way to stuff it back in . That's a great analogy ; finding a NYC address or becoming the best NY cabbie. Be safe...Bob.

[EagleMark]

I admire the intrest! But when your done you would be an expert on something that no one wants to use... never goes bad... and only comes into play if you mess up your prom burn or run without a chip...

[Six_Shooter]

I plan to one day, work out how the NETRES and RFD work in the P4 style ECM, but is not very near the top of my list. I did buy an O-scope as part of figuring out what does what on the NETRES, but I haven't found an official internal schematic of those NETRES DIPs, so I haven't started building my adjustable version yet. I know how I will I will go about testing changes, just want to make sure I'll have an accurate placement of the adjustable resistors to do it.