This is my first post here and I have to say this board has a tremendous amount of technical depth, you guys are lucky. I have learned that this is the place to go for GM ECM help.

I actually drive an 87 GN and have recently been learning to make my own PROMs. I have had a lot of success playing with the look-up tables. Basically its a MAF type car similar to many of you guys here.

I want to understand the code. I have been struggling to learn assembler and have a well documented listing of what's in my ECM. I followed the code from power on reset through to an infinite loop. I think it must sit there until some type of interrupt occurs which makes it jump somewhere else. I want to know if there are any good references on how GM implemented the basic operation of the code? I am not a software type but am willing to learn.

I hope GN guys are allowed here.

 

Welcome to TGO ! There are a couple of GN guys here and ALOT of smart people here (especially on the DIY-PROM board)!

I'm sure you can get any answer you need here.

What program are you using to tune your .bin's with?

 

Here is a thread that has a blurb on the basic operation of the kernel:

https://www.thirdgen.org/techbb2/sho...+AND+interrupt

I know there is another thread that goes into more detail on the kernel but didn't find it. See the sticky's at the top of this forum for a bunch of good info. Should get you started.

RBob.

 

Thanks for the links, I will study them.

I forgot to mention I normally hang around TurboBuick.com, I think I recognize Grumpy from there.

As far as editing goes, I tried the TunerCat trial version. I found the TunerPro interface better but on my computer its not stable for some reason, it crashes every few minutes. The main reason I got into PROMS was because my MAF tables were rich on the bottom end and lean at the top. I can't figure out how to get the TunerPro ECU file to incorporate the MAF table scalars, I have to hard code the scalar for each table in the ECU file.

Other than editors I have been doing some brute force Hex editing.

My winter task is to understand the ECM code.

 

I'd suggest you investigate the 1227749 like the Syclone's use.
Either way an ecm bench is a real time saver.

The 749 has all the code in a memcal is alot easier to work with if you want to modify the code later. Not to mention the faster ALDL, and no MAF.

 

WOW!!!

 

I know I'm off topic here, but man that looks fast Grumpy!

Back to topic.... How difficult is it to get the syty code to run with DIS? This is of course for WAY future projects......

 

Looks like Barney, the purple dinosaur.

The DIS operation has been done with other ECM's that used distributors, There was a bit of code re-writeing to do but it supposedly works good.

 

What rewriteing was needed?.
Which other ecms?.

 

Hehe.... First look at the new 4.1 boogie monster.

I need to get busy with the 383..

BW

 

Someone on the GMECM list had done a hack and patch of one of the TBI ECM's to run DIS. Don't remember their name but they did get it working (according to them) with a bit of work.

 

Could you try really really hard to remember there name . I wouldn't mind trying this out if it allows me to run either wasted spark or CNP.

 

Wish I could remember, I know it was asked by a member and he was reffered to someone else on the list that said they had it working (on a TBI application). About all I can tell you is that it was posted a few months before the list went belly up and the person that had it working was someone that post to the list much any more...wish it could be more info.

 

Maybe someone needs to ask Barney then.

http://home.woh.rr.com/brucesgn/749togn/

 

eDist allows either.

DIS for a v8 using GM stuff means Northstar, and they're $$$.
Unless you want to use dual ecms/sensors. Or develope a Klingon Language Translator.

GM's done about all the combos, you can imagine, you just need to poke around the junkyards to find them thou. Then it's just a matter of pasting the pieces together. That sometimes is easier then what you might imagine, it's generally a matter of looking closely to see what's going on.

 

It's actually a 4.202L
Or for most folks, justa v6.

 

Yeah I know about the eDist but I really don't like the price. If it came with the coils and wiring harness then I'd be all over it. The fact that $300 for that little box plus the coils plus time mounting and wiring = not worth it just yet. My valve springs are the softest little pieces of junk that having CNP would result in zero results. Besides, I think it's fun telling people exactly what I have done to the car and them saying... and msd right?... nope, stock 180k mile dizzy and coil .
Eaton m112 might need a little more spark energy .

 

if you wanna talk about the 60* v6 and the 4cyl modules. the problem with those is that they cant calcutalte dwell for advance greater then 30* btdc. aarrgghh so you have to retard the timming 60* atdc to get 30btdc advance. does that makes snes ? no but thats how they do it. not to mention that the Ref pulse comes out at TDC. so the module is always one cycle behind the ECM. ill have to get off my lazy *** and post up the data ive got together on this in the near future. Since there are some folks hording it up.

Id like to get the 90* v6 3.8 timming vs ref vs EST line stuff together as well as the stuff for the n* and the lt5. but im wiating to get an actuall lt5 module to figure that pos out.

 

Well, the retard 60* to get 30* advance does make sense, but only after you mention that it's one cycle behind. So, the code spits out the new timing value, and it takes until the next cycle for it to update? Why it works this way is more in question than anything. It would seem they could it the same as a regular HEI module. Hmm....Maybe I need to think about it more.....

I bet that LT5 module is a hard to come by piece! The N* isn't as easy as I once thought, but I think it would still end up being cheap to find a used setup than the eDist. Not to mention the coolness of using all GM original parts!

 

the reason the modules are one cycle behind is becuase

One revolution to get a fix on crank position, then another revolution to create a delay long enough to control the module.

wierd but true. its not a code problem. its the way the module is designed.

 

The code is based on DRPs, not engine revolutions.

You don't need to overthink, it, all.

The LT5 is $$$, and at one time was discontinued, thou I heard rumor there were some more modules now in the system. Northstar is just $$$.

 

Make some new friends, and design your own. The ecm figures everything out timing wise. A simple count to 4 (DIS), and 8 makes for CNP, resettable with the cam signal is all it takes.
I bought a set of CNP coils off of eBay for 150.

 

yeah but the way the module behaves isnt at all based in ECM distributor world. it holds the DRP's till its got 2 sucessful revolutions with no resets. this way it knows its in sync. Ive had tons of trouble with this so ive rigged up a few test with Pulse genrators just to be srue.Then off course it runs Ahead of the ECM but in timming world it runs behind. Ill post up the data i have here really. soon.

The way the EST codes vary between the dizzy and DIS setups has to do with the way the modules behave. Id be fiarly certian in thinking that the N* v8 stuff should work fine with regular v8 code advance retard settings . But i havent had time to hash it out. the LT5 looks the most promising. And yes there are plenty of LT5 modules avaiable. Right now im trying to locate the lt1 mercuiser DIS setup that ran on MeFI2

Last bt no least is my Quest to use 2 4 cylinder modules to run a v8. its easier then you think. just gotta toggle the EST properly.

 

The modules all are wired the same, in their interface to the ecm, from what I've seen. So while the code may run a little different, it still ends up the same hardware wise.

Knew about the toggling, but still don't really see the point in all of it. All it takes is using a dual sensor distributor. Then an eDist or something similiar.

 

No doubt. the hardware is all the same. in fact a regular l98 maf ecm could run a optispark if there was a trasnlating box to interpret the hi and low res tracks into a 4 drp per revolution sigal. the thing with the various modules is that some of them have different dwell calcs that require different ratios in advance retard splits. thats all. i havent had time to finish sorting it all out code vs module etc but i will.




i like the idea of 2 4cyl modules. cheaper then an edist and if one goes bad you only out $75 instead of $300 for a whole edist. plus what if i break down in the middle of kansas with a bad edist. i can go to autozone and get a module.