[DML] Carburetor Tuning

[Bob Brandys <BobB@xxxxxxxxxxxxxx>]

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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