Smog test say what about health of engine

[percyives]

Can you infer any thing about the health of your engine from the test numbers from year to year??? Also if extra Zinc (added to oil) is bad for my catalytic converter , can then a cat bypass be made to produce good smog test numbers on an 84' 911 with 140,000 miles?

[vmisquez]

Your answer to this question and more may by found in Milt's book
TUning up Autos and Trucks by Milt Webb. You will even learn how to diagnos and repair computer controlled engines.

http://www.milttheinstructor.com/

[Peter Zimmermann]

Originally Posted by percyives

Can you infer any thing about the health of your engine from the test numbers from year to year??? Also if extra Zinc (added to oil) is bad for my catalytic converter , can then a cat bypass be made to produce good smog test numbers on an 84' 911 with 140,000 miles?

Everything depends on how the engine is tuned. If the idle speed and CO% are within factory spec, but you have high HC, it could be an indication that your car is burning oil (which, of course, will also be reflected in your consumption rate), or have some sort of a combustion chamber related problem develop since the previous smog test or tune up. Usually bad numbers (vs good) at smog test time will be a product of something fuel injected or ignition related. In any case, if your smog test numbers are bad you should always take steps to find out why.

In L.A. I would say that having a car without a cat pass smog would be just about darn near impossible.