[DML] Carb vs FI
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[DML] Carb vs FI



The statement that a carburated engine could not meet 1981 emission standards is wrong.   Way back then I was in charge of testing thousands of vehicles in the chicago area for emissions as a public service through the American Lung Association.

The 1981 emission standards were essentially the same as those implemented in 1975 which required the addition of a catalytic converter.   GM and other car makers met these emission standard with carburated engine as late as 1986.  90% of all emission in the EPA test methodology come from starting the engine when it is cold.  Quick heating cats solved this emission problem. Thermo reactors were even used by Mitsu and Chrys to speed up this heating process. 
Ford put the cats right on the exhaust manifolds to achieve the same effect. 

Carburated engines can be as efficient as FI engines BUT it is a lot more work to get a carburator to do this. 

FI can be controlled with electronics to measure fuel delivery to easily compensate for the individual engine variations that occur in the manufacturing process.  However, carburators do not have this flexibility.   To achieve maximum fuel efficiency from a carb you need to put the car on a dyno and adjust the jets accordingly to get the maximum fuel economy.   This is a long and expensive task to do.  BUT IT CAN BE DONE. 

The best example I know of this is a friend who has a 1969 Camaro with a 501 and a Quadrajet.   He also works for a research company that tests additives for cars.  They have a dyno to test effects.  

Fortunately, he has free access to this dyno and the equipment to measure emissions and fuel consumption.  He spent almost a month of evenings dialing in his 501 to get maximum fuel economy.  

Did it work?   Well, he gets over 20 mpg at 60 mph.  I would say that works.  I don't know of any FI engine of this size that gets 
anything close to this mileage.  


The reality is that the choice to go to FI by the car makers was done to get better mileage and NOT to meet emissions.  

Bob


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