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CeC technical information?

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MIPS View Drop Down
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    Posted: Apr/27/2019 at 1:55pm
Has anyone ever spent time reverse engineering how the 6-cylinder CeC was built or any technical documents for the computer? They seem to be in the realm of "unserviceable if bad" due to how they are potted or at least, I'll have to destroy a computer to find out on my own.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2019 at 4:01pm
Have not reverse engineered but sometimes they can be "repaired" if it's moisture from cracked or separated epoxy.
Just clean the unit, wire brush the case and epoxy edges, flush with WD40, put in an oven for 2 to 3 hours at 160 degrees, and then pool in more epoxy.
Works some times, and if it does work the unit will last for years of service.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote MIPS Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2019 at 8:32pm
Oh, mine works. I'm just more curious exactly how it was constructed and how a modern replacement could be provisioned. I've basically finished with the electrical and operational theory for all the sensors but now it's cracking the computer itself open to determine what type of microprocessor they used (and where it loads its ROM from), how the interface buffering works and if there are any other secrets hiding in the potting, which no matter what way you do it will be a destructive ordeal and will require a sacrificial unit.
People who are both skilled in automobile mechanics and electrical engineering isn't common.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Apr/29/2019 at 6:23am
Well, it's a GM system, so you might find some info on GM sites. Most people abandon it if it stops working, going back with a non-computer carb and distributor. Many forget that the distributor is part of the equation and use the original. That will work, but you really need a non-computer dizzy for best engine operation since it is calibrated differently.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Apr/29/2019 at 10:19pm
i've made a lot of software-driven electronics for car control, including a completely software-driven cooling system (no belt-driven pump, no thermostat). i have no idea what CEC is beyond feedback carb, but i can tell you what the replacement *electronics* would be -- a modern microprocessor, a few MOSFETs, and a half dozen glue components. times have changed.

all functionality of any kind is done in code. LONG GONE is doing *function* in electronics. it's too brittle, costly, inflexible. purpose-written code is flashed into nearly generic hardware.  my car has three computers, networked, that do various things, and the hardware for each is exactly the same (except one has adds a big LCD, SDcard, controls, etc).


here's my cooling system. i do highly reliable electronics in an automobile environment. the devil's in the details.

auto electronics from the 80's or even 90's is so fantastically backwards and barbaric from what can be done today, there's no contest. it's like comparing a 2018 Corvette to a Model T.

code and electronics: https://sr-ix.com/Code/index.html



Edited by tomj - Apr/29/2019 at 10:49pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Apr/29/2019 at 10:48pm
btw, the best place currently to find nifty controller and electronic stuff these days is Adafruit http://adafruit.com. run by Lady Ada, aka Limor Fried, really good designs, good prices, lots of information, free software, drivers for everything. i love everything they do there.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Apr/30/2019 at 12:05pm
Sometimes you can remove the potting gump by boiling the item in a pot of water. You still have to do alot of scraping though....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MIPS Quote  Post ReplyReply Direct Link To This Post Posted: Apr/30/2019 at 9:03pm
You're pretty much doing exactly what I have in my head, just with a lot more complexity, which is fine as you've done quite a few more things beyond adapt a new computer to an existing system. Your whole site was well worth the read.

I could sit down and pretty easily build a shield for the CeC in an evening. It's like, six 12V digital inputs, four digital outputs, a two phase stepper motor output and an analog 1V O2 sensor input. Without fully understanding yet how quickly the CeC performs the feedback loop you could in theory use a microcontroller as small as the Arduino Pro Mini, which is about the size of a person's thumb, to replace the entire computer, assuming your code fit in the 32Kbyte flash memory.

I suspect that unless GM or AMC at the time was paying for custom semiconductors, the CeC uses something to the tune of an Intel MCS-48 or MCS-51 microcontroller.

Edited by MIPS - Apr/30/2019 at 9:08pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Apr/30/2019 at 10:32pm
i suspect you're right. GM used a slightly-custom 6811 in the "TBI" systems everyone (used to) adapt. dunno what quantity you'd have to order to get custom silicon. Motorola (used to) offer limited OEM quantity semi-custom in 10,000 to 100,000 unit quantities but that was the 1980's. today 100 MHz is no big deal!

so carbs lasted 90 years, then from around 1980 through say 2000 there were "feedback" carbs, electronic/mechanical/hybrid FI, throttle body FI, etc. by ~ 2000 it's port injection and now, direct injection. that stuff in the middle is mostly awful, like "microminiature" electron tubes like Nuvistors, 12V plate tubes for car radios, thickfilm, cordwood, all that awful electronic crap from the 50's and 60's before monolithic silicon. mostly feedback carbs and mechanical FI are horrid curiousities for restorers....

but personally i considered an electronically controlled computer -- for performance and fun-to-make purposes -- might be interesting and practical. the problem is that th base part itself is just to crappy to work with. some crap old smog 2bbl isn't a good basis for anything.

as far as i got was thinking about ... so what would be worth closed-loop control? to me, it would be main jet tuning and altitude compensation (which are really the same thing). analogous to the GM TBI map system, look for errors in the "map" (load vs rpm) lean/rich, and a table to tweak the mix by pulling the control rod up or down. but since this is a stepper with a cntrol rod, it wouldn't be a realtime adjustment like TBI map, but a slow (60 sec? 5 min?) scale that worries more about steady state cruise, and ensure rich enough during high load.

i've considered writing my own EFI -- because it's fun, not because i think i could do better than say MEgasquirt -- but it's a looooot of code for little benefit.

OH MAN! Megasquirt these days is handling X-tau now! that's the phenomenon of what happens when you squirt gas into a runner -- most of it goes down the hole with the air, but some of that wets the runner walls and valve, and that wetted-out fuel then evaporates with a time constant that depends on temperature and other factors.

a feedback carb compared to current Megasquirt (never mind what additional magic OEMs do now) is like a stone age club compared to an airplane.

for me, it's a carburetor, a nice "simple" (right!) mechanical thing, or full-tilt-boogie software, eg. Megasquirt. and this is probably my last carburetor.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/30/2019 at 10:38pm
hi, just fyi, the early units may be GM sourced, but the 84+ units are FORD, and are still available at any auto parts place, about $200.  or so. biggest difference is the early ones control carb only, 84+ control carb AND timing. thanks, gz
george z
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