GM CCC carburetor: Variable manual stand-alone controller

Thread Starter

Aguila1

Joined Apr 7, 2017
6
1st post. Novice. As I understand it:

The GM Command Control Carburetor (CCC) uses an ECM to control a Mixture Control Solenoid (MCS) that operates a paddle with two small spring-loaded metering rods, cycling at 10 Hertz, duty cycle fixed. Ground applied, the magnetic field pulls the plunger (and paddles and metering rods) down into the main jets, leaning out the mixture. Ground circuit de-energized the springs push the metering rods out of the jets, going to full rich. The length of time the MCS is on or off, plunger up or down, is varied by the ECM signal, depending on inputs from the O2 sensor.

A dwell meter can measure the computer control signal, 30˚ being half the time up, half the time down, as the computer uses the inputs from the O2 sensor to try to maintain a stoichiometric air fuel mixture. It varies the time up or down, according to the air fuel ratio detected in the exhaust.

I would like to run the CCC Quadrajet carburetor but without the ECM, to be able to visually read an air-fuel meter gauge to make changes on the fly while in light cruise mode, so that I can run different blends of gasoline to ethanol fuel and also, since ethanol is more resistant to lean mixtures without causing detonation issues than gasoline, I would like to run the engine as lean as the engine will allow by manually leaning it from the driver's seat for maximum fuel economy.

What type of device could take the place of the ECM to energize and de-energize the MCS at the same 10 hertz cycle and allow manual variability?

It has been suggested to vary the voltage input that normally comes from the O2 sensor and run that into the ECM, but prefer not to have a computer at all for simplicity's sake, as it easily goes into default open-loop mode meaning no MCS operation, full rich in the primaries, when it detects an anomaly.

I appreciate your input.
 

tcmtech

Joined Nov 4, 2013
2,868
Why do you think you need to go leaner? If it's for fuel savings you are going the wrong way. It seems counterintuitive at first but the fact is going richer than stoichiometric with gasoline and ethanol blended fuels improves power and fuel milage not makes it worse.

The problem behind the misconception is that stoichiometric ratio, ~14.7:1 by mass, is the point where the most fuel gets turned into CO2 and water vapor when burned but is not the A/F ratio where the maximum amount of chemical energy is most efficiently converted into mechanical power which is what matters when you're trying to save fuel and money.

With gasoline that happens around 12 - 13:1 and gets progressively richer with more ethanol being ethanols stoichiometric ratios is ~9:1. It's easily confirmable with any engine that has a older style carburetor that has adjustable main and idle metering jets. Richer A/F ratios up to a point make more mechanical power using less air and less fuel. Especially with ethanol blends.

I've worked with this sort of stuff for well over two decades now regarding how to get the power and efficiency back out of engines that are emissions compliant plus with just old engine to gt them to run right on today crap fuels and going leaner is not it as so many seem the think it should be.

Post 32 for more details. https://forum.allaboutcircuits.com/threads/vw-not-so-clean-diesel.115588/page-2#post-903127
 
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Thread Starter

Aguila1

Joined Apr 7, 2017
6
Why do you think you need to go leaner? If it's for fuel savings you are going the wrong way. It seems counterintuitive at first but the fact is going richer than stoichiometric with gasoline and ethanol blended fuels improves power and fuel milage not makes it worse...
I appreciate the input, but I still want to run the carburetor without the ECM, if only to have that variability from richer to stoichiometric to leaner on the fly. The theory will be easily verifiable once the car is moving and it may very well turn out that leaning out the mixture will show no gains at light cruise, as you express.

Any ideas on controlling the electronic end of things here?
 

tcmtech

Joined Nov 4, 2013
2,868
A basic 555 timer IC can be easily set up to do fixed frequency PWM control or fixed duty cycle variable frequency as well.

The bigger problem is that a vehicle engine does not have a fixed A/F ratio throughout its entire throttle and load span hence the reason the older all mechanical carburetors had the complicated variable jetting systems.

Depending on throttle position engine RPM and load the A/F ratio varies a fair amounts by going to a manually controlled A/F ratio system you will find yourself needing to make adjustments every time you change load and or RPM range. At light loads and low RPM' you may be able to run rather lean, ~15+:1, Without issue but when you step on the throttle all it will do is bog and have no power until the A/F ratio is turned up to being on the rich end ~12:1 or better.
 

Thread Starter

Aguila1

Joined Apr 7, 2017
6
A basic 555 timer IC can be easily set up to do fixed frequency PWM control or fixed duty cycle variable frequency as well.

The bigger problem is that a vehicle engine does not have a fixed A/F ratio throughout its entire throttle and load span hence the reason the older all mechanical carburetors had the complicated variable jetting systems.

Depending on throttle position engine RPM and load the A/F ratio varies a fair amounts by going to a manually controlled A/F ratio system you will find yourself needing to make adjustments every time you change load and or RPM range. At light loads and low RPM' you may be able to run rather lean, ~15+:1, Without issue but when you step on the throttle all it will do is bog and have no power until the A/F ratio is turned up to being on the rich end ~12:1 or better.
The A/F ratio is turned up (richened) by turning the electronics off in this system. The CCC Quadrajet ECM controls steady cruise in closed loop. At large throttle openings it goes into open loop, full rich, metering rods spring-loaded up out of jets, solenoid off and the mechanical secondaries work like every other older model Quadrajet carburetor. I just want to control light cruise A/F ratio at a steady-state rpm. Maybe also connect to O2 sensor for those inputs (0.1V lean to 0.9 rich), but just have a manual override to run leaner, as an experiment. Studying the 555 and potentiometers, all new to me. Appreciate the input.
 

tcmtech

Joined Nov 4, 2013
2,868
As interesting and theoretically hopeful as tweaking the A/F ratios manually as you wish sounds in reality it's about as practical and fun as driving with an automatic transmission that been rigged to do manual gear shift operation only. The problem is the type and range of driving where such conversions are advantageous are so tiny in normal day to day driving conditions they prove to be a fiddly pain in the ass real fast.

I suspect that you will quickly find the adding a manually controlled extra lean burn adjustment mode to your vehicle will prove to be of such a limited application and larger hindrance it will be more of a problem than anything gainful. Even in very good highway driving conditions the throttle rarely stays in one position and the engine at a stable fixed load for more than a few 10's of seconds or longer where any lightload fixed RPM driving conditions could take advantage of it.

However what does make a big difference on older vehicles with carburetors or electronic controlled carburetors and has bee proven to be the most effective ways to pick up power and fuel efficiency are not overly difficult.

Increasing the distributor advance limits to add another 5 or so degrees of advancement range so that the ignition advance can go higher at light engine loads.

So is blocking off or bypassing the EGR circuit so that it either does nothing or draws fresh air from ahead of the carburetor which improves light load engine efficiency .

Same with reducing exhaust system back pressure by either removing the catalytic converters and going a larger low restriction high flow exhaust or at least a Cat only system which makes for noticeable improvements as well.

Also and if equipped with a smog pump stripping that whole system off and removing all the lines and related hardware that went with it does good plus cleans up the engine compartment considerably.

Lastly cheating the O2 sensors output signals to read a bit the exhaust as leaner than it is at ~12.8 - 13.5:1 A/F ratio (closer to the power and efficiency A/F ratio but not too far out of working limits) as stoichiometric by adding a low forward drop germanium diode (~.3 volts) in series with their output helps a lot too.

Over the years I have done many of these types of emissions systems gut and cheat jobs and every one of them gave justifiable improvements in power, performance and above all fuel mileage gains in return. Especially when all were done at once and the combined 10 - 20% gains in power and fuel efficiency most vehicles get from them could be seen all at once.

Sure they probably wouldn't pass a california emissions test afterwards but at least they could pass another vehicle and gas stations like never before! :p
 

Thread Starter

Aguila1

Joined Apr 7, 2017
6
Lastly cheating the O2 sensors output signals to read a bit the exhaust as leaner than it is at ~12.8 - 13.5:1 A/F ratio (closer to the power and efficiency A/F ratio but not too far out of working limits) as stoichiometric by adding a low forward drop germanium diode (~.3 volts) in series with their output helps a lot too.
To be clear, you are suggesting having the O2 sensor give a false leaner voltage so that the Q-Jet compensates slightly richer? Do you have any links to studies backing up this supposition, that richer plus timing, etc. will net better fuel economy or is this based on personal experience, having tried both richer and leaner? Is this experience on gasoline only or a 50%+ ethanol blend?

I'm having a hard time wrapping my head around how less emissions in the exhaust, i.e. leaner mixture, could result in worse fuel economy, though the idea of larger volumes of leaner mixture because of larger throttle openings is not lost on me. I always thought that leaner would produce more power, as in on the leaner side of the enriched power mixture, and thought the same would apply at small throttle openings.

I was also under the impression that ethanol fuels have unique characteristics suitable for lean running, as witnessed by the winning mpg entry, the Edison2. I believe they chose to run E85 for this reason, beating out other cars running on gasoline.

As to all the other tips, great minds think alike, as all are implemented. Another factor that I haven't mentioned is having a turbocharger, which may contribute to superior atomization and some vaporization of the fuel even at cruising rpm.

If interested, to see the complete engine build, go to Vimeo and put Pontiac 301 in the search. I have not installed the new engine, yet, as I am still working on the car.
 

tcmtech

Joined Nov 4, 2013
2,868
The concept of reaching the A/F mixture to gain power and fuel efficiency has been around as long as emission systems have been in use. My Grandpa worked at a local Ford dealership for ~40 years from the late 50's - early 90's and got first hand experience with the cheats that came out as the emissions requirements and technology advanced.

When the first emission compliant vehicle came out auto mechanics quickly started figuring out what was done and how to improve it. #1 fix for crappy fuel mileage and power was to turn the ignition advance up to where it was on the pre emissions engines specs and rejet the carburetors to the old richer A/F ratios. After that knock the guts out of the catalytic converters and blocking off the EGR units plus removing all the smog pump related gear was next.

Its not just my concept but one that has been well understood and practiced since the first emissions compliant vehicle came out and they proved themselve to have worse power and fuel milage number than their predecessors with identical engines the year before and everyone wanted to know why.

As for why leaner doesn't save fuel the physics are fairly easy to understand.

First when you burn the fuel it has to heat up the air to make it expand so if less fuel and more air is present more energy for the smaller mass of fuel goes into heating the air then before leaving less total energy available to do any actual mechanical work.

Second, the hotter the air is the more expansive force it creates which if short of fuel it cant reach as high of cylinder pressure which means less expansion force is available to push the pistons down on the power stroke. That's how your throttle works. Less air and fuel less combustion energy is available. Add more air but not more fuel and more energy goes into heating the air leaving less for making mechanical power which is what you base your power and fuel economy on.

Also with emission systems the catalytic converters have to be above a certain temperature to work which in a mechanically efficient engine at light throttle loads the exhaust gasses are not hot enough for them to work. In order to overcome that problem that were retarding the ignition timing plus making camshafts that open the exhaust valves early plus injecting fresh air into the exhaust with pumps came in.
By igniting the A/F mix later in the power stroke plus opening the exhaust valves early more of the combustion heat energy could be dumped into the exhaust to keep the converters hot enough all the time. Plus by injecting more air after the exhaust had left eh engine any unburned fuel could be burned to help things along enve more. All things that take fuel energy that ultimately does not go into making any productive mechanical motion to move the vehicles whatsoever.

With the advent of modern EFI and some clever engine redesign cheating they were able to eliminate the smog pump systems by changing the camshaft profiles to allow more air to be pumped through the engines themselves but that air still needs to be heated the same as before during the combustion process and power stroke and come out the exhaust hot enough to keep the converters working properly.

To do that camshaft profiles were changed to dump way more of the power stroke combustion gases off early but that reduces the effective compression of the engine so we get what we have had for ~ 4 decades now which are engines with impressive sounding mechanical compression ratios of 9 - 11+:1but in reality there effective compression due to the massive amounts of bleed off is for many a dismal 6- 7:1 actual or similar to a 1940's tractor engine.

As with you I have built engines myself. Years ago I rebuilt a 1977 Ford 460 from a lincoln to put in my pickup to replace a emissions compliant 351w. I built the big engine to be as efficient as possible which meant replacing the crappy early emisons camshaft with a proper and efficient heavy towing camshaft plus did major port work. Also I went for the stock ~7:1 compression ratio to near 10:1 so it could run well on propane.
From start to finish on the 460 I picked up about 2:1 on HP and about 40% on fuel milage at the same time! Plus having ~400 HP and 500+ ft/Lbs of torque on propane made it crazy fun to drive!
Compared to the 351 W it was a near 3:1 rear wheel HP gains and double the fuel milage.

Another engine I built for special application propan only operation was a old 1980's Mazda B2600 with a 2.6l I4 that I got cheap because of a blown gasket due to the previous owners (some kids) trying to run it as a lean burn engine and not knowing what they were doing with the electronic carburetor system. I had the head milled ~.80" to get the compression up to around 12:1 and modified the camshaft drive to retard it about 15 degrees to cut down on the compression dumping.

End result was an engine that put out more power and got better fuel mileage numbers on propane than it was ever rated for on gasoline. I drove it as a daily driver and run around beater for about two years before it broke a piston ring and chewed up one cylinder.
 

Thread Starter

Aguila1

Joined Apr 7, 2017
6
...First when you burn the fuel it has to heat up the air to make it expand so if less fuel and more air is present more energy for the smaller mass of fuel goes into heating the air then before leaving less total energy available to do any actual mechanical work.

Second, the hotter the air is the more expansive force it creates which if short of fuel it cant reach as high of cylinder pressure which means less expansion force is available to push the pistons down on the power stroke. That's how your throttle works. Less air and fuel less combustion energy is available. Add more air but not more fuel and more energy goes into heating the air leaving less for making mechanical power which is what you base your power and fuel economy on...
Not so simple or obvious. So, you're saying basically that the engine will produce less power in lean burn, but isn't it also a given that a lean engine runs hotter? How do you square having hotter air, but less mechanical energy (pressure)?

How is fuel economy based on mechanical power, when lower power should translate into less fuel used? Certainly a Ninja 300 gets better fuel economy than a Ninja H2R 1000.

At cruising speed, my car might only require between 10 and 30 hp, so making more horsepower is less important than using the least amount of fuel necessary to get down the road, short of lean misfire.

I agree that drivability can be improved and even mileage over the factory set-up, as you have proven, but have you left any fuel economy on the table by not running max lean? Did you even run an O2 sensor to verify what you were running? Did you measure A/F ratios? If not you may very well have been running lean on propane and not been aware of it. What did the 460 get, best highway mileage, just curious?

Here's one of many articles that I have read where lean burn strategies are being experimented on with ethanol based fuels:
http://www.matec-conferences.org/articles/matecconf/pdf/2016/08/matecconf_icmm2016_03003.pdf

I appreciate the discussion. If I did want to lean the mixture electronically from the O2 source, how would one go about that? Could I just add a potentiometer in line before the ECM?
 

tcmtech

Joined Nov 4, 2013
2,868
Not so simple or obvious. So, you're saying basically that the engine will produce less power in lean burn, but isn't it also a given that a lean engine runs hotter? How do you square having hotter air, but less mechanical energy (pressure)?
It starts going into the realm of detonation combustion processes like diesels use.
A very high peak temperature and pressure is made but the burn duration is so short and hot that it does not transfer its energy to the mechanical components to make motion as efficiently.
It's what makes the knocking and hard pinging noise when a lean burning engine sees any load similar to how an over advanced ignition does. Too much cylinder temperature and pressure is being created too fast for it to be converted into mechanical power.

It can be cheated a bit by retarding the ignition to put the combustion cycle start point after the piston has reached TDC but in doing so the transfer of energy from fuel to mechanical motion suffers which is basically what EFI systems and the low effective compression ratios are doing just to make stoichiometric combustion work without knocking and pinging at load or excessive bogging and intake side backfiring.

It's also why you can't transplant a stock EFI system from a modern vehicle onto the engine built to pre EFI and emissions compliance standards.
At the stoichiometric A/F ratio the EFI system would be wanting to run things at the non emissions engine setup would have too much compression and the wrong camshaft profiles to handle it.

With propane things are different being it's a gaseous vapor fuel that does not need to be vaporized/atomized in the engine to burn.
It doesn't really have a too lean and thing go bad condition either It just has a point where the power starts dropping off and gets worse from there and that's it. I get to experience it every time my propane tank runs out of fuel and I have to switch back to gasoline operation.

As for my old pickup, with normal light driving it got around 13 - 15 MPG on propane. Even when pulling 10,000+ pounds at interstate speeds it was rare to come in at under 9.

I had it for about two years before a little old lady took the front end off of it and totalled it. After that it got replaced with my 1999 Ford F250 Super duty with a V10 which on propane gets ~9 on light driving and 4 - 5 on heavy towing plus doesn't hold a candle to the old pickups power especially when towing.

What is interesting is that being a stock emissions spec engine there is no real difference in its power or fuel milage between propane or gas like the old pre emission engines had a bad reputation for.
By default of being emissions compliant they are detuned to the same performance that the old gasoline engines running on propane had.

Also unlike the gasoline fuel side that's all computer controlled A/F ratios, the propane system is a simple all mechanical system that runs off a simple vapor mixer unit that fits between the air filter and throttle body so the computer had no say in what goes on regarding fuel.

On top of that with propane it burns so much more efficiently that the computer sees the O2 sensors as being too lean and too cold to function properly so they have permanent error codes logged because of that. So interestingly enough despite having far less energy per gallon its ability to turn its fuel energy into mechanical power makes up for it and the miles per gallon values stay similar.
In fact with a high profile camshaft (heavy towing/lower mid range performance and slightly lopey idle cam profile) and high compression it can actually top gasoline on power and fuel efficiency (wont really give the lopey idle though being the burn characteristics tend to cancel it out) !
 
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tcmtech

Joined Nov 4, 2013
2,868
I am an automotive technician and I agree with Tcmtech. Good luck.
Thanks for the agreement.

I find these sort of discussion interesting largely due to how many common misconceptions about how engines and vehicles and the related physics behind them in general actually work.

I've been in many like this where someone wants to get better fuel milage or have a lower cost per unit of distance traveled simply by giving their engine less fuel to work with yet keep the same power and drivability while doing so.
To do that everything comes down to how the engine is built and the sad reality that no modern emission compliant engine is built to be as fuel efficient as it can be. They're built to meet the specifications of the emissions requirements and fuel usage to do so was not on the list of concerns in those requirements.

The #1 misconception is that a clean burning engine is a fuel efficient one. Nope. It's just really good ad burying all the fuel with minimal residues and byproducts beyond CO2 and H2O. To do that it actually fuel energy to mechanical power conversion efficiency is compromised and with many engines compromised a lot. A gasoline burning engine built for peak efficiency can run about 20 - 25% on fuel energy to mechanical power conversion where as a emissions compliant engine is far less. Often down in the 10 - 15% conversion range with the best modern ones falling in the 15 - 18% range.

Now being a 15% efficiency Vs 20% doesn't sound like a lot being it's only ~5% of the fuel energy content being lost but that 5% difference is a full a full 1/4 or more loss in potential MPG numbers wise which is where we all place the value of a vehicle's fuel efficiency at. Then to take it further when comparing an engine that was severely detuned to meet emissions compliance that barely touches %12 efficiency (mid 70's and newer V8 engines were often in that 10 - 15% at best range even though with proper design many were capable of the ~20% and some even higher.) compared to a well designed and built specifically for fuel efficiency engine that runs in the 20% - 25% fuel efficiency range that's a full 2:1 differential on MPG numbers.

As for what I have seen myself it's interesting to see how old vehicles of the past actually compare to to day stuff and it's sad.
Me and my family own and have owned a number of old farm trucks from the 1950's to 1970's and it always amazes me that I can take my dad's old 1960's Ford F600 grain truck (~12,000#'s tare) with a 330 CI Ford industrial engine go to town get 7 - 8 tons of gravel ( 26,000+ #'s gross) and have a round trip fuel mileage average that is the same or better than my 99 Ford F250 gets on gasoline doing the same trip with nothing but my flatbed trailer (~11,000# tare and ~20,000 #'s gross) for the exact same trip and the exact same speeds.
The worst part is when talking to the old timers who ran those old Fords new it was common knowledge they were not the best on fuel at the time for loads hauled either! :(

The big heavy aerodynamically challenged 1960's box truck uses the same amount of gasoline as the smaller lighter far more streamlined emissions compliant modern pickup pulling a flatbed for the same trip and identical driving conditions. :mad:

BTW if you really want a kick in the head compare any modern car or pickup by it's weight and aerodynamics to those of any class 8 or larger commercial semi rig. I have driven those for years and it really makes you wonder what's going on when a 80,000 # 400 - 500 HP semi rig gets 4 - 6 MPG running at interstate speeds while my 8000 pound Ford F250 gets 6 - 9 MPG or my 4000# Mercury Grand Marquis (before the emissions system delete and retune job) got ~18 -22 MPG (upper 24 - 27 to occasional low 30's after). Hmm.... :(
 

Thread Starter

Aguila1

Joined Apr 7, 2017
6
And that's the reason why they don't run them lean, also, as leaner than stoichiometric produces higher NOx, a component of smog and acid rain. If I am not mistaken, the rules that apply to gasoline, do not translate directly to E85 use. As in your propane experience, whenever I have run leaner at light cruise, in a moderate compression engine, right up to lean misfire, the point when the car starts to buck, I did not experience detonation. Granted my brief experience did not net better fuel economy than on gasoline, so I do not discount what you are saying totally. I ran in the neighborhood of λ1.05-1.28, colder temperatures (about 40˚F) made drivability worse, though that might have been icing of the carb.

You just can't compare an oxygen-bearing fuel like E85 directly to gasoline. Way lean reduces NOx, though.

Lean-burn vs. rich burn:
"Lean‐burn engines use a lot of excess air. Usually up to twice the amount needed for complete fuel combustion. This air dilution effectively cools down the peak combustion temperatures in the cylinder; that reduces the NOx production and allows low engine‐out emissions without the need for an after treatment system in many applications. This lean combustion process has the additional advantage of reducing the knock (detonation) probability and, therefore, allowing higher BMEP (Brake Mean Effective Pressure) levels (loads) and an optimized combustion phasing. This results in higher power density and usually produces better fuel efficiency."
http://www.gallois.be/ggmagazine_2013/gg_04_07_2013_148.pdf

GM work on lean-burn engines:
"Lean operation shows significant fuel economy improvement at light to medium loads."
https://energy.gov/sites/prod/files/2014/03/f10/ace063_smith_2012_o.pdf
 

tcmtech

Joined Nov 4, 2013
2,868
Chrysler played around with the lean burn concept in the 70's and 80's. In real world driving it proved to be marginally better but overall the amount of cost that went into setting up an engine to run that way on purpose didn't pan out in the long run.

It can be done but it can't be done reliably with a non specialized engine built specifically to handle that type of operation. The chance for piston and valve meltdown is very high even with modern control systems so unless the engine was built to work as such I have serious doubts the bit of fuel saving it may produce will ever offset the costs of what burning your engine down costs.

It's interesting to experiment with but the reality is if the big auto manufacturers are not using it and the ones who tried gave up on the concept there is a reason why.

As for Nox production that's another common misconception. Higher NOx production when weighted as its GWP value Vs CO2 for the same engine power achieved don't add up to what they are implied to be.

https://forum.allaboutcircuits.com/threads/vw-not-so-clean-diesel.115588/ Post 17

:oops:

Higher NOx production has nothing to do with emissions compliance. In fact Co2 or environmental anything doesn't either. What it does have everything to do with is making everyone burn more fuel in order for the government to collect more fuel tax.
As far as the oil companies are concerned they would love to sell us half the fuel at twice the price. More profit for them and less work to get it, we pay the same per traveled mile as before all while producing the same or likely less environmentally concernable byproducts as well. The problem is the government loses billions on fuel taxes in the trade. :mad:

Personally when I decided I had had enough with high costs per mile for fuel I just switched over to run on cheaper fuel. Around may parts road use propane is typically bulk rate plus road tax which works out to about 1/3 - 1/2 the cost per mile the end and that's the numbers I care about. :cool:
As far as all of my other vehicles and equipment plus most everything else that has an engine is now set up to run on E30 or higher blend fuels which around here tend to run a good 40- 60 cents a gallon cheaper most of the time. ;)
 

MrSoftware

Joined Oct 29, 2013
1,676
I only skimmed this thread so I hope this makes sense; but if you want to adjust the mix on the fly, to some extent maybe you can hijack the throttle position sensor. To go leaner reduce the feedback voltage, to go richer increase the feedback voltage, essentially making the computer think you are giving it more or less throttle than you really are.
 
This was a fascinating read. I can identify with Aguila1 in this thread as I, too, had it in my mind it would be better to just wire the mixture solenoid to an Arduino ticking away on a PWM output, easily interfaced with and formulaically integrated with the O2 sensor, and dial in the best overall "feeling" with a pot. Am I understanding now that we *want* the variable mixture in our lives, even if my end goal on this engine is to remove everything not directly contribiting to the operation of this machine.

The reason I'd want to do it is I'm running (roughly) again after performing a double head gasket surgery. After starting post-build, i've replumbed the vacuum hoses, removed the evap canister and hoses.

I'd love to block off the EGR due to $100 replacement cost, remove the smog pump and piping, remove the cat, I'd love to lose the dumb EFE valve back there in all that heat.

I have a new O2 sensor that goes in at first light. But I'd also like to remove some things to tame the mixture and timing problems I'm having, there are some serious variables in the extensive vacuum system this poor engine doesn't need to be fighting while I restore its organs.

But I fear I'm going to be treading on the computer's turf , and the fun police in the ECU will shut the frigging car down with a "LIMP MODE" activation, which I understand means slamming the mix to full rich. So, I'm down to lose the computer so I can get this beautiful car moving again, but my bank account isn't rich in carburetors. And I'd rather put an OLD V-8 in there if I'm suddenly considering buying a chrome carburetor for a dumb 231 V-6.

What, in your opinion, is the bare minimum emissions intrusion on a Buick block 231 V6 3.8l engine system to still retain a diplomatic relationship with the 1981 California CCC computer? Please, go general, that's just the patient on my operating table at the moment.
 
What, in your opinion, is the bare minimum emissions intrusion on a Buick block 231 V6 3.8l engine system to still retain a diplomatic relationship with the 1981 California CCC computer? Please, go general, that's just the patient on my operating table at the moment.
I don't have experience with GM really, but I do know in 81 automotive ECU's were pretty basic. Emissions laws didn't even come into effect until three years before your car was built and most of it was done with differences in vacuum or pressure rather than sensors and actuators. Does the ECU also control the spark advance or just the fuel mix? If possible your best bet is to swap distributors (I'm assuming it has one) to a standard vacuum advance, figure out how to dial in the mix, and delete the ECU. Of course the EPA and any emissions certifications won't like what you did, but that's up to you.

I'm assuming the California CCC refers to the car's ECU. If I'm wrong never mind me and you're probably stuck putting everything back the way it was to start.
 
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shortbus

Joined Sep 30, 2009
7,463
What, in your opinion, is the bare minimum emissions intrusion on a Buick block 231 V6 3.8l engine system to still retain a diplomatic relationship with the 1981 California CCC computer? Please, go general, that's just the patient on my operating table at the moment
Why not just do away with the computer all together? Get the intake, carb and distributor from one of the very early versions of the engine family. They were available in cars other than Buick and should be found on Ebay, but I didn't look to see.
https://en.wikipedia.org/wiki/Buick_V6_engine#231
 
I have designed a simple 555 timer circuit that uses the TPS to adjust duty on a 10Hz signal from 50% to 90%. It is in a LTSpice format. Its a free simulation program that has a schematic and simulate view.
 

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