The Sy/Ty's were batch fired, just like the L98's. However, if a V6 can make that kind of power, what could you do with the same code on a V8? Some people have found out.....Do a search for $58 code. Grumpy also has his version out there, and from what I've seen of it.....nice... I have a feeling that's what I'm going to be running, even though I'm not planning to be running boost (yet?) It runs on a '730 with repinning.

(Sorry to repeat this for those that know this already, it just seems that not everyone knows about the $58/$60 stuff yet!!!)

 

32V_DOHC,
I stand correct yet again, thanks.


Question for anyone who has opened a 2240 or Northstar PCM...

Does the 2240 or the Northstar PCM have an unpopulated space on the PCB for a IAC driver. Like for example in the 730 there is an extra unused solder pad space for a second injector driver but GM only used this space to put a second driver for the 749.

 

Just need to use a 94-95 PCM since they were sequential, but still OBD 1.

 

Here's some interesting ECM/PCM info...


http://www.cruzers.com/~ludis/p4xref.html

 

Ok, one more for tonight....

In any of the V6 SFI (Buick engine) ECM/PCM's, did GM leave room for 2 more injector drivers? I haven't looked into this myself, but is there unpopulated circuitry to add 2 more cyls to make a SFI V8? I know this is WAYYY too optimistic, but ya never know!!!! Besides, I don't have one lying around to look at.....

I'm just trying to exhaust all options here! Like I said before, I'm not very worried about SFI, but all tyhe other stuff is pretty interesting to me......

 

Sorry to say, that magazine article simply has it wrong. They were batch, not sequential.

Edit: Ooops, didn't notice that had already been mentioned...sorry!

 

I probably confused you further by saying "8X sensor" instead of "pick-up coil". That's all it is, and just like a regular HEI, it provides 8 pulses per distributor rotation to the ignition module.

The hall shutter (a totally separate sensor) activates once per distributor rotation, i.e. once every cam rotation, or every other crank rotation. Without that, the ECM would have to fire in batch, because it would have no way of knowing where/when to start the sequential injector firing sequence.

I'm sure if you had an actual distributor in front of you, all this would be very obvious. Sorry I can't describe it better.

 

The more I think about it, the more I'm convinced that the 94-95 LT1 PCMs are the way to go. For what I'm after (individual cylinder trim for a smoother idle), it appears to be the only way. Even if an earlier SEFI system could be made to work, it wouldn't give me this feature. I'm sure the SEFI itself would help, but it couldn't be optimized.

 

If you go the opti route you can also run DIS with the delteq unit. It costs $350 for just the bare minimum unit . If the northstar PCM has a unused prevision for a IAC driver in it that would be a cheaper choice in terms of running DIS but it would require a lot of code work which i don't think there is enough interest in for.

 

Found a site with a ton of great 4th gen info... schematics, photos, assembly diagrams, the works!

http://shbox.com/1/4th_gen_tech1.html

 

Here are the part numbers for the 94-95 LT1 Opti ECM and all the cars that used it to help you find one in a junkyard.

Part Numbers: 16181333, 16188051, 88961150
Cars:
I think a big downfall of this ECM is no emulator support. If the flash chip is de-soldered is there way to wire up a 28 pin socket to PCB and use a emulator? Or is the flash chip not pin compatible with the standard eprom?

 

I kind of think emulators are over-rated. The PCM allows you to reflash it with the engine off which is more than adequate. Make sure you use a RS-232 device in the ALDL cable.

Yes, you can desolder the chips. There is two of them........so you will need two emulators or a big single. The flash chip is compatible with some standard flash parts (after a code change??). I think it looks for the proper chip in the stock bin. Maybe some of the emulator professionals can jump in and give the details. From what I have seen, most of them skipped the LT1 PCM because it was just to complicated for them to figure out and no one will tell them how to do it. But yeah, emulating with the LT1 PCM is possible.

 

Put the opti portion in the distributor as the pictures show. You'll have to get the high tension side out of the distributor by using a Delteq or LTCC. I use the LTCC and love it because it has a true studder rev limiter and 2 step built right in. The 94-95 PCM is simple to switch to Speed Density ( that actually how I'm running mine right now). You'll get SEFI, O2 feedback for both banks, and control of a 4l60E trany if you like.

 

The LT1 PCM isn't really that complex, but the coupling of the emulator to the PLCC memory starts looking pretty retarded pretty fast. You can also couple to the memory address /data lines at one of the internal headers, making it a bit cleaner, but it still starts looking pretty ghetto by the time you're done.

One of the Flash chips holds the majority of the engine calibration data, whereas the other holds other info such as OS from what I understand. So, you can probably get away with emulating only half the memory.

Anyways, I was headlong down the path of doing an emulator for the LT1. Have several split cases kicking around the workshop. But they were only viable for a short time compared to other ECM/PCMs. It's still doable, I mean it's just slow old 8-bit Flash memory. Not very big either. A pair of 8-bit emulators, going at it Ostrich-style on the address muxing, should be able to handle it easily. Just need to wire it up. Make sure all the address and data lines are hooked up correctly.

I found a source for some rather nice PLCC-to-PCB headers when I was looking. Check www.adapters.com and you'll find some cool stuff. You could easily build an interface. Like you say though, you'd need to push half the binary to each of the two emulators.

Gets into lots of wiring with very little real estate.

I wonder if the LS1 PCM could be fitted up to some of these older applications? Then you could go right to a crank trigger and true DIS. Worth a thought, there's just loads of those spare parts kicking around these days and even more in the future. Realtime emulation and binary editor support is already available for the LS1 stuff, with generic OBD2 datalogging you could be good to go. Just a thought.

Anyways, if anybody wants to build an interface harness from the PLCC memory of the LT1 to adapt to emulation, go for it. Not that bad, but you'll get into clearance issues unless you have some imagination.

 

The way I understand the PCM's is that it is more like 2 in one. There is a E side and T side. Which stand for Engine and Transmission. If you are running a manual or have your tranny set you don't need any real time emulation for that.

 

You're right, that's consistent with what I understand as well. One for the engine, one for the tranny.

 

If I'm reading the $EE right in Tunercat, there's a switch in the switch tables that converts the PCM to "Speed Density Mode". That's how intend to run mine.

 

You are reading correctly. Check that box and dig in to the VE tables. There is a VE master program somewhere for the 94-95 PCM but I have'nt tried it. I did mine the old fashioned way. Oh yea, there is one downside to the 94-95 PCM, Once you hit about 7100 or 7200 RPM the PCM crashes TOTALY and shuts everything off. You then need a key off and key back on the reset everything.

 

VE master for $EE is pretty worthless. Your VE table starts to look like somebody took a hammer to it with all the dents in it. You're better off doing it manually by looking at the best learned cells and fixing those well learned cells to not move once corrected. Then make the cells around it will less learning more "conforming". The end result is much better when you do it manually.

 

The wireless emulation thing you were talking about would be great for the LT1 PCM.........no wires sticking out.

 

Uhhh... somehow I'm not too concerned about that...

 

Yet...!!!

 

I never heard of that happening. I wonder if it is supposed to or it is a code bug. I wouldn't worry about it for low rpm engines. There is a greater change of an external emulator picking up RF noise and causing an ECM malfunction......and no one seems to worry about that.

 

The high RPM crash happens for sure. Many on CZ28.com have experienced it. I have done it myself (by accident) on my 94 - 355 Formula before I installed the LTCC with a decent rev limiter. The High RPM crash is one of the reasons some of the 4th gen crowd moves up to DFI.

I'm not too surprised about VE master garbaging up the tables. That's kinda why I did it with logs and pivot tabes in excel spread sheets.

Steve

 

This is something I really want to do although my new job has taken up most of my spare time at this point.

I've looked at transplanting the guts out of the opti and placing them into a large cap HEI. I see two possiblities.

First: Cut down the opti base and bolt it into the large cap HEI. The reluctor could be turned down where it then could be press fitted into the bearing assy. for the Opti disc. It would also need a couple of other Mods.

Second: Find someone with a CAD/CNC of a SBC Dizzy and redsign the top of it like that of a Opti Base.

Why would you want to just run SD??? When GM first came out they were running Mass Air Flow cause this is a more Efficient way of measuring air. The problem was that the MAF sensors were burning out and causing problems. Then they went to MAP (Speed Density) for the 90-92 TPI's. When the LT1's came out they were now using both . This allows the PCM to compensate for a wide variety of conditions.

Just my 2 cents worth
Bill

 

lol, don't even start with the "why" questions. You and everybody else KNOW why! So please don't ruin the thread with loaded question like that.

 

The simple answer is I don't want to buy an expensive MAF sensor. However, I'm going to run the wires for it so that later if I change my mind, it'll simply be a matter of hooking up the sensor and turning the SD switch off in the PCM.

 

I agree on the don't ask why. I myself don't know WHY. If you start another thread on why everyone knows, I would be interested in reading it.

The MAFs can be had for a reasonable price at a junkyard. Making the duct work takes a little time. Anyone ever thought if just installing a Digikey opto coupler in the GM HEI?

 

ULTM8Z, I wasn't trying to be smart, I just didn't understand. Thats all.

Thats a smart move by planning ahead and running the wires. BTW, I checked out your EFI Guide, good job. It will help the younger rodders comming up. I bought a Opti and tore it down this past spring along with a couple of Large Cap HEI's. Looking to see what the best method is in mounting the guts. I'm going to look at them again and tell you what I think sometime tomorrow.

For Others: To help someone you have to understand what they are striving for or trying to achieve. Then you can work with them to accomplish the goal. This is a part of teamwork. The Chinese have a saying "Gung Ho" which translates "Working in Harmony." When I've posted here before about using the 5081 with a TPI, Grumpy would ask me Why and then he would share his knowledge, thoughts and insights on the subject. I wouldn't get upset with him or make comments. I would read and re-read his statements trying to learn from what he was trying to teach or tell me. If I still didn't understand I would ask him to claify his answers. After a career in the military, working as a technician, and teaching the past 8 1/2 years, I realize that people don't all learn the same way or think the same. I do however, try to show others respect.

Don't get me wrong, I'm not trying to upset anyone or "Ruin the Thread." I didn't grow up with electronics or computer code, but I do have a high mechnical aptitude. If we are all striving for the same thing and I believe we are. Then by workin together I'm sure we can accomplish the goal.


Bill

 

Bill, no worries. I didn't take it that way at all.

 

elcamin0_77us, there are a bunch of threads regarding MAF's in thirdgens and other vehicles. Lots of theory, lots of proof, very little actual back to back testing!
How do you know your "facts" are really just that?
Where is it written from dialog through the engineers at GM that the MAF was a "more Efficient way of measuring air." or "The problem was that the MAF sensors were burning out and causing problems." is true... because I've seen a bunch of 18+ year old MAF's that have been through a LOT but are still working original equipment.
The only thing you said that I will agree on is the statement, "This allows the PCM to compensate for a wide variety of conditions." with regard to running both MAP and MAF inputs. Any time you give the computer controls more feedback the better the job it 'can' do .
I apologize for being short with you. I'm just used to trolls coming on this board and starting ****. My fuse has always been short.

 

There's absolutely nothing wrong or inferior about the LT1 MAF system. I only switched to SD because I thought the MAF was causing a restriction in my intake tract. I'm not convinced that it really is a restriction yet. I have a 4" CAI system and a very large K&N filter and still can watch the MAP drop from 101 to about 94 KPA at 6900 RPM. I sorta figured I was leaving some ponies on the table with that kind of drop.

Steve

 

O'Kay, I understand where your coming from.

Bear with me for a second. I grew up in Illinois and attended a area Vocational High School. I had concentrated in two areas of study one being Automotive. With my military career being cut short due to a hearing loss, I went back to school for update training. Even though I had continued to do my own repairs while in, computers had just started comming out when I Graduated High School. The local tech school had a pretty good program in which I attended. While a student, I took and passed 4 ASE exams half way through the program. This was the early 90's. Durning this time period Carquest would hold classes for the local shops and dealerships using factory trainers. My instructor had worked out a deal with them to allow his students to set in for free. I was able to set in on several factory clinics at that point. Most of the classes given were on drivability. According to the Factory Trainers, they had had problems with the wire in the MAF getting dirty or even burning out. Even after I graduated from the tech school, I continued to recieve factory training. At one point I even worked at a GM Dealership. This past summer I attended a week long training session given by GM, Chrysler & Toyota for Georgia Automotive Educators. My job requires me to have update training each year, which I complete. I said all of that not to brag but to explain where I was coming from.

John Baechtel talks about the differences between MAF & MAP in two books that he has written. "To keep cost down, most systems use speed-density control. This eleminates the expensive MAF sensor, but also some accuracy, since air flow is calculated rather than measured. Engine maps for speed density are very high quality and you generally won't noticed the difference, but maximum accuracy is still obtained with a mass air flow sensor supplying precise information to the ECM." Another quote from John "A mass flow fuel system adapts easily to changes in the engine as well as hardware because air flow is measured directly. In other words, a mass flow system is self-compensating for most reasonable changes to the engine and is extremely accurate under low-speed part-throttle operation. The downside is that the sensors are expensive and sometimes unreliable."

John Lingerfelter states "Mass Airflow-A second form of multi-point EFI is mass airflow where the engine actually measures the amount of air that the engine consumes through the use of a (MAF) sensor. The computer then plots this information along with imput fron the MAP, TPS and other sensors to determine the amount of fuel to be delivered to the engine. While more accurate than speed density, the (MAF) also increases the price and complexity of the system."

I know GM has been in the news lately, but think about it. They started out using mass airflow systems, went to speed density and then back to mass airflow with a MAP sensor. Why would GM make those kind of changes? In the classes I attended given by Factory Trainers, it was due to the unreliablity of the MAF Sensors. Once they had fixed the problem they went back to the mass airflow system. It was also determined that the MAP sensor would help overcome some of the limitations of the mass airflow system durning high-speed full-throttle operation.
And when John Baechtel and John Lingerfelter make statements such as those, I for one am not about to disagree.

Remember one last thing, I'm not here to cause problems but to help and learn that we might come up with a fesible way to run a TPI using a 5081 thats documented that others can build as well, not just pictures or rumors floating around the net.

Bill

 

I've been studing my opti spark & Large Cap HEI as well as some pics of the Small Cap HEI & the converted Opti Dist. In the past I had really wanted to use the Large HEI, but my conclusion is that the Small Cap HEI would be the way to go. It will be easier to mount the base of the Opti on the Small Cap HEI due to the fact the base is flat & the way the rotor attaches. It seems that they cut off part of the opti rotor to allow the shaft to go through. Then they used a collar with two set screws. I believe at this point I need to pick up a Small Cap HEI. This really should be quite simple with the aid of a lathe.

Bill

 

They both use mathmatical modeling so the arguement about one being more *direct* then the other is nonsense. Either type is no better then the tuning.

Have Lingenfelter or Baecthel written any code, and spent alot of time looking at the code end of things?. Obviously not, since they both make the same errors, and misstatemtents.

GM for reasons of OBDII added a MAF back into the system. The MAPs were doing just fine.

Not asking questions is just following the herd, and get the *sport* no where. BTW, I've been to a few GM classes, and have had instructors recant what they've said.

MAFs have a inherit error in that they report not only the engine air flow, but the air reguired to change the vacum level in the manifold. In the later codes a fair amount of code is used just to correct this error.

 

I believe this point that Bruce makes, along with high-biased errors around idle associated with resonant inversion, are key.

The MAF/MAP thing is a 'personal choice' thing for most. With MAF, you can change things up on the motor, and not much tuning is really required. With MAP, your VE relations change significantly with cam and what-not, and you need to compensate.

There's no free lunch with any of this, gotta keep the engine's needs in mind, and consider all the dynamics. My personal choice is MAP (730). I haven't found a need for SEFI. But if I were going to go that route, I'd probably go with the LS1 setup with a crank trigger. That would get interesting.

It's kinda funny, I've been helping a guy locally here tune the LS1/LT1 motors, and what we do is turn off the MAF first of all. Leave it on for data collection. Then we go into the SD mode and collect all the data: RPM, MAP, measured AFR via WB, target AFR via PCM, LTFT/STFT, plug readings, calc air via PCM (SD), and meas air via MAF. Then we go in, populate some data space, and start moving the VE table around to compensate for the LTFT+STFT and the TARGAFR/MEASAFR. Run it a couple more times until the VE is correct, and then look at the comparison of CALCAIR/MEASAIR. Then modify the MAF table to 'correct' the MEASAIR.

So actually using feedback (WB, NBFT, plugs) to calibrate the VE and then using the VE to calibrate the MAF. Then put the car back on MAF for daily driver duty. Kinda backward, but it proves a point or two I think. Works fantastically.

So that 7000 limit is for real on those LT1s eh? That's pretty harsh. Didn't know about that. Tell you what, I like the idea of a distributor instead of optispark in any case. It'd be interesting to see even a regular LT1 converted in this way.

But back to the thread subject, you think you'll be able to get good enough spatial resolution in a dizzy-mounted sensor? It's pretty tight in there, and you're talking a lot of teeth. I'd think the crank sensor would be the way to go in that regard.

 

I don't know which is better. I do know that the teaching/instructor world is much different than the design world.
The purpose of training is usually just to get your feet wet. In order to understand things you usually have to research the material further. The training instructors usually get second hand info that is published by the designers. So if you really want the truth, you have to go to them.
With either sensor it all comes down to the control algorithm that uses the information from the sensor. With a good control algorithm and good tuning I think that they would be about equal. Reliablity is a different topic on its own.

If you really want to learn about something, you have to read up on it and do your own experiments to see how things actually work. Second hand info will only get you so far. This isn't targeted at anyone, or MAFs or MAPs, or anything in particular. It is just a general statement on how to get to the bottom of things.

The LT1 PCM is a great system because it has both MAP and MAF. A nice system to experiment on.

 

Ummm, why? Want kind of resolution do you think you need? How much is a lot of teeth? Maybe you should think about it again?

 

Actually, I was jumping ahead I suppose or back or sideways or whatever. I'm talking about a non-opti-spark system. Something that uses a different pick-up rather than optical and encoder wheel. Optical is one thing, LT1 is one thing. I was thinking more generally, if you could go toward something more DIS in nature eventually. It'd be nice to see some crank trigger options that are coupled with stock PCMs. Put some decent electronics between the trigger wheel sensor and a trigger box, and get rid of the distributor altogether. One less moving part to worry about. Just trying to think outside the box. Something like a 'DIS Translator' for stock PCMs.

 

Grumpy, Point(s) Taken. I get what your saying. Myself I haven't had alot of time to play with codes. Its something that I would like to get a chance to do here with in the next year. Thinking about it, I have had classes where the instructors say remember what we said about bla-bla-bla well we were wrong, here is the correct info.

Craig, You also mades some good points and even explained how to go about tuning this beast once I get it up and running. But I not sure what you meant by this:

The disc out of the opti is just over 3 inchs wide and includes identifying marks for both the 8 cylinders and the 360 degrees. Is there something else I need to be a ware of?

This is an idea that I've been kicking around for several months. The opti rotor holds the disc in place on the mounting pad. Take a round aluminum stock and have it machined with a collar with set screws, to act as a replacement for the rotor. What do you think?

Bill

 

No outside the box thinking there....more like you said,...backwards. People have been doing that for years. A few of the tubo guys are running DIS and many others that I don't know of. Take a look a the Ford V8 DIS or aftermarket. I believe this has been covered in DIY PROM many times before.

Back to topic, Does the opti-wheel need the bottom of it machined down to fit the shaft? Or is it the inside diameter that needs to be machined?

 

Nevermind, I give up...

 

The inside diameter is a little large on the opti mounting plateform which leaves a gap between the mounting plateform and the dist shaft.

Bill

 

Incase your not following my terms, I'm not sure what the correct terms would be, here goes. The base is the aluminum base that everything bolts too. The mounting plateform includes the sealed bearing and the plateform that the disc fits onto, which inturns bolts into the base. The rotor or rotor button then bolt down to the mounting plateform holding the disc in place.

If a piece was machined like the rotor it could have a collar with the inside diameter the same as the dist shaft outside diameter. Does this makes sence or am I out of my mind?

Bill

 

Don't give up. I was just trying to get you to think about it a bit more. If you look into the Ford DIS you would end up finding the circuitry or "DIS translator" that you were talking about. Not trying to offend you, just trying to get you to look into it.

The Opti (cam ref) and crank trigger would be ideal. The crank trigger will only get you DIS. You need the cam ref for SEFI. I still have no need for SEFI.....but this has got me thinking for the future. Time to keep an eye out for opti-dis when junkyard searching.

 

It makes sense. It sounds like a decent option from the pics I have seen.

 

You guys come up with a working copy and I will put it in a CAD system complete with jPegs, drawings, etc. If you can get a opti working properly I will do solid models -everything and anything that a shop wants or needs to make them. Next step would be a group purchase. The other direction would be a crank wheel like a MSD? My personal preference would be to stick with GM stuff.

Craig BTW I noticed your tuning methods. There are some mail order chip tuners that are pretty popular with the LT1 crowds. I have personally seen a chip that was done for a friend with a fairly large Comp cam. While there was some significant tranny tuning, the engine side did nothing in the way of VE tables. In fact the tuning was from what I remember maybe some timing in the upper areas and PE tuning only along with making it idle. These guys swear by the tunes. I told then if their MAF ever went out they would be lucky the car would run. I suggested that they go to SD mode and tune a rough VE table but they got rid of the car. In all fairness the tune they had ran 12.8 in the quarter with a 3:42 rear gear on a auto tranny.

 

I have found that MAF LT1's need a little recalibration of the MAF table when camshaft starts to get some overlap. Most of the work needs to be done in the low airflow areas of the table. WOT is handled by PE table just like the older stuff. Another useful add in is a program called BLM locker. The LT1 PCM has a nasty little habit of going into one of 2 cells at WOT. It is believed that it always chooses the cell that adds the most fuel. This can kinda hose you up at the track cause fueling can change from run to run. BLM locker forces Learns to 128 at WOT. It works perfectly.

 

I think I'm late to the party with this info, but...


regarding ISC vs. IAC stepper motors, I think a simple interface could probably be created.

Example:

http://home.cogeco.ca/~rpaisley4/Stepper.html

With a bit of additional logic (probably a couple transistors and resistors) the output of the caddy ECM could be made to ground the appropriate connections on S2 of the circuit design described above. I'm sure there are other circuit designs too, probably even available from the manufacturers of stepper motor drivers as generic designs for their chips.

You'd end up with a fixed speed step output based on the caddy motor outputs. If the caddy ECM had variable output voltage (to turn the ISC faster or slower), then additional logic could be implemented to have multiple step speeds (perhaps some kind of ADC with the outputs hooked up to varying resistor values to supply the R1 resistance in the schematic above)?

Just some thoughts for the EE's out there. I don't have the experience or knowledge to design such a circuit, but i would definitely volunteer to solder up a prototype PCB/build the first working model from a schematic and see how it works.

 

91L98Z28,
There are stepper motor driver circuits everywhere on hobbyist sites like you linked to. I also think the output of the ECM could be converted. The 2240 isn't worth doing though because it doesn't have individual cylinder trim and no knock sensor, just makes it a lot less attractive and not worth the effort.

Though there is a PCM that I would rather use over the Opti PCM, the Northstar PCM. For the reason that the Northstar setup is DIS and uses a memcal. The problem is the Northstar PCM also uses a type of non-stepper ISC motor.

This could be taken one step further and possibly building a converter circuit using a IAC driver de-soldered from a old ECM with some interfacing circuitry.