[DML] Re: Carburetor Tuning
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[DML] Re: Carburetor Tuning

You also have to agree it is a lot faster, easier, and cleaner to "adjust" an EFI system. In fact, you can do it while you are driving! There are other reasons the automakers were encouraged to computerize the emissions system. Some of them have to do with the EPA and their regulations. For instance try passing emissions testing with your Check Engine light on! The system self-tests. Can't do that with a carburetor. It will also detune if it is knocking on bad gas (like too much Ethanol!). It is also a lot harder for the backyard mechanic to mess with the A/F ratio without the right (expensive) equipment. The EPA is heading towards a 100,000 mile service interval with "Locked Hood" and a cell phone to call the Dealer if the motor is running "out of compliance" so you can get a letter telling you if you don't have it fixed your registration will be revoked. Your car will "turn you in". If your car is stolen (or the Police are chasing you) they can turn your car off. On the plus side, cars are MUCH more reliable then they used to be. Good thing, not very many mechanics out there that are smart enough to fix it! As for catalytic converters on carbureted cars, does anyone remember the air pumps? They used them to pump air into the exhaust manifolds to "afterburn" the left-over fuel so it wouldn't contaminate the cat. It turned the manifolds cherry red and usually failed after a couple of years. By then all of the pipes were rotten and the manifolds were cracked. The top of the motor looked like a spaghetti factory with all of the vacuum hoses to make it all work. With all of the underhood heat it dryed the hoses out so they all cracked and leaked. Couldn't find all of the leaks so we just replaced all of the hoses! The "Good Old Days" were not so good.
David Teitelbaum

--- In dmcnews@xxxxxxxxxxxxxxx, Bob Brandys <BobB@...> wrote:
> In 1975 when catalytic convertors were first installed in cars virtually all of them were carberated. 
> Catalytic converters lasted for 50,000 miles by federal law with these carberators. 
> In the 1975 and later Quadrajet, there was an atmospheric compensator that adjusted the idle circuit for atmospheric pressure. 
> Other car manufacturer "computerized" carberators, with an idle air solenoid that was connected by computer to an oxygen
> sensor.   
> Clearly, these carberators worked with catalytic convertors all the way until the early 1980s.  
> Carberators can be tuned to give almost equivalent mpg as fuel injection but this must be set up using 
> a dynamometer and an exhaust gas analyzer.  
> I have a friend who set up his 501 camaro to get 21 mpg on the highway with 3.08 gearing and turbohydromatic. 
> My dad had a carberatored 1980 Buick Century with V8 that 29 mpg on the highway, with a 3 speed automatic NOT overdrive. 
> It got this great mpg until about 149,000 when the timing chain slipped. 
> What computerized fuel injection did is allow the fuel system to automatically adjust for the variability of each engine and 
> it induction system.  
> Early automotive pollution research showed as much as 25% variation in air flow on the same engines size production
> engines at the same rpm.  It was not cost effective to individually adjust carberator for this variation. 
> But computerized fuel injection systems would do it automatically.   
> Some of this individual engine variability has been reduced.  The best engines still have about 5% variability.  e.g. the "better"
> engines go into the corvettes. 
> Computerized fuel injection can adjust for a lot of variable conditions, but carberator can still function almost as well if properly tuned.


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