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How much power, what mods can a person do to the '81 and maintain the CCC system? Yes, I'm well aware it can be removed and replaced with STD carb and distributor, but has anyone left the CCC active with the E4ME carb and done heads and more with success?
Already replaced the exhaust from the headers back with a true dual.
CCC aka Computer Controlled Carburetor was the last attempt to make a carburetor emissions friendly .
If you’re trying to keep the system working properly then Camshaft will probably be the limiting factor and you won’t be able to go much over stock duration and lobe separation . Those TFS aluminum cylinder heads with the 175cc intake port and small combustion chamber would add power without messing with the CCC , you just can’t throw a big cam at it
I think you can install upgrades to the point the capacity of the Q-jet is exceeded....and that is quite a lot, compared to the stock '81 power output. Q-Jets were placed on large BB engines from the factory, so they are not the limitation. Heads, cam, pistons, intake, etc. could all be modified and the control system should still work. All it does is adjust timing (based on throttle opening and engine speed) and try to maintain a good A/F mixture.
the ccc is overridden at about 35 mph cruise. all it does is look at exhaust O2 level and TRY to optimize idle and part-throttle O2 levels. basically up to just a little faster than the speedo reads on the emissions-i guess it is a half-*** dyno. i guess the compromises a high horsepower cam forces on the engine at low throttle could make it really freak out. as soon as you hit the gas, it is a q-jet. i still feel the best place to install that system is the bottom of the river. if it works now, that 40 year old ecm is just waiting to pop.
Last edited by derekderek; 07-02-2021 at 10:32 PM.
Tell us what you really think, derek.....
Do you have any reference info on the "overridden at the 35 mph cruise" statement? That system was used for a few years on other Chevy models (into the 1980's). I'm pretty sure the carb was 'managed' beyond 35 mph.
This thread is pretty much how it goes when trying to discuss how to get more power using state mandated smog system.
There has been a smattering of information over the years but the good info is spread out in many threads.
The CCC carb will flow as much air and fuel as a reg QJet.
Basically the vacuum POWER VALVE has been changed from a SPRING controlled valve to an electro-mechanical valve.
This power-valve is controlled by computer.
Where this system fails is when VACUUM signal gets too LOW.
Thus, any big cam-shaft that lowers idle vacuum below a point, the computer gets lost and doesn't know how to control the power-valve or ignition timing.
There it is in a nutshell.
The MAP sensor can't send a usable number to the computer when the engine vacuum is at or outside its operating specifics.
A lot of discussion about finding a different map sensor that will work with lower vacuum than stock never really panned out.
Discussion about hacking the chip fails because the map sensor just can't send "value" to the computer anyway.
The floor of what idle vacuum will work the MAP sensor I believe is around 15 inches?
Been a while since this was on my mind.
I see a lot of 81 owners lately, would be nice to have another real talk.
There are a handful of people here who has knowledge.
What device sends the vacuum signal to the ECM? MAP Ssnsor? Couldn't you just install a device with adjustable calibration to compensate, if that were the issue? If not, then I guess the cam would be the limiting factor for engine upgrades with the CCC system. Need cam with decent lift without a lot of overlap. Still could make a 'healthy' engine out of it.
There were discussions about some device between the map sensor and computer to fool the system.
If I have it right,
the system uses 5vdc and the map sensor sends full 5v when vacuum is high and less volts as the vacuum drops.
seems there would be a need to UP the volts from the map sensor to the computer to fool the computer that vacuum was high.
The other method would be to search for a gm car that uses map sensor on an engine that from the factory puts out low vacuum?
This would be my preferred method if I had access to what gm "map" motors that run 15in or less at idle from the factory.
That map would see 15in and send 5vdc to computer.
This is great information. Looking at the ECM itself, I do not see anywhere that vacuum is monitored or affected for the engine other than emissions controls: the amount of vac is not utilized for the distributor timing advance, nor does it affect the carburetor operation unless I am missing something?
https://www.gmheritagecenter.com/doc...oduces-CCC.pdf more of a press release than tech pub. but some useful info. no. it doesn't say what rpm or throttle setting it goes to full rich, but the vacuum operated version can be set like a holley power valve from about 5 to about 14 inches of vac. i don't recall where i read my previous statement. but it really only cycles the power pist up and down at a 10 cycles per second rate. they set it to be at 50% dwell at idle. so they were trying to manage idle fuel too so they must have the actual idle mixture set too lean as the vacuum power piston will be pulled down tight into max lean at idle. and trying to manage idle fuel with the main jets says a bit about how desperate they were to clean up the emissions enough that they could even sell the car.
Last edited by derekderek; 07-05-2021 at 12:10 PM.
Very cool article!! Apparently, this was an internal AC-Division newsletter detailing the CCC system [probably copied from a GM news release]. I enjoyed reading it and learning about the details of the CCC system. Everyone on the CF with an '81 C3, or those considering buying one, should read this and keep a copy for reference. One thing that was new to me was the "idle speed actuator". But I'm not sure if that is a separate device or it that is part of the fuel mixture control's function.
The system diagram on page 2 clearly depicts a "Barometric Sensor" and a "Vacuum Sensor".Can anyone who has an '81 with working CCC system provide more detail about those devices? (photos and/or part numbers)
Key on engine off it’s a Baro sensor, engine running it a vacuum/ load sensor so the computer can figure out if you’re going up hill (low vacuum )or down hill (high vacuum ) and adjust metering rods accordingly.
Key on engine off it’s a Baro sensor, engine running it a vacuum/ load sensor so the computer can figure out if you’re going up hill (low vacuum )or down hill (high vacuum ) and adjust metering rods accordingly.
in a real quadrajet, the power piston is vacuum actuated. in the E4me it is driven by a solenoid. cycling at 10 cycles per secont. like an injection nozzle the time up-rich and down-lean is varied by what the oxy sensor says. it is set up at up-down 50% of the time at idle. the old q-jet idle was-is set up with vacuum holding that piston down. i am not guessing here. and yes, they would never have come up with this desperation play that ONLY controls air-fuel at part throttle and idle if the epa didn't tell them they had to do something to hit better numbers than they hadda hit the previous year. from 72 to the late 80's everything they did everything they thought about was emissions.
Last edited by derekderek; 07-05-2021 at 01:14 PM.
06-29-2021, 07:51 PM
1981 CCC power limitations?
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