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post #1 of (permalink) Old 09-04-2003, 09:40 PM Thread Starter
 
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Air Tube & Cat. Conv.

Just wondering if anyone can further explain the purpose(s) of the fresh air tube on the exhaust system. Is it's only purpose emissions or does it serve others? If I leave the air tube unconnected will I notice a performance decrease or could I damage other components of the exhaust (i.e. cat. conv. or mufflers)? Thanks for the info.

BTW.. I'm nearing the completion of my 5.0 HO swap into my '80 CJ7. The last big step is the exhaust which has prompted this post. [img]images/graemlins/smirk.gif[/img]

Lee
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post #2 of (permalink) Old 09-05-2003, 02:03 PM Thread Starter
 
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Re: Air Tube & Cat. Conv.

ptt... anyone? [img]images/graemlins/crybaby.gif[/img]
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post #3 of (permalink) Old 09-05-2003, 04:25 PM
 
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Re: Air Tube & Cat. Conv.

Hmm...I'm not sure for your application, but I would guess you wouldn't need it. On my 85 CJ7 they have you block off both ends of the air tube, at the cat and at the manifold end, when you do the Mopar MPI conversion.
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post #4 of (permalink) Old 09-05-2003, 05:27 PM
 
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Re: Air Tube & Cat. Conv.

I may be misunderstanding the 'air tube' your asking about but... I believe that tube allows unburned emissions to return to the manifold to be burned before the exiting the cat. If you have no sensors like O2 or temp on your cat it should make no difference whatsoever.... unless you have to pass an emissions test.

I may be wrong but I have a similar situation on my 89 wrangler and that was the info that I received elsewhere.

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post #5 of (permalink) Old 09-05-2003, 06:11 PM
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Re: Air Tube & Cat. Conv.

On my '82 Scrambler ( had [img]images/graemlins/censor.gif[/img] CA emissions), the air tube on my cat was hooked up to the air pump in the engine compartment.

I was told the fresh air pumped into the cat. permitted the cat. to convert the more harmful emissions into the less harmful emissions (CO2, etc.). I understood the fresh air permitted/aided the catlysts to do their job (more efficiently).

Whether I was told 'right' or not, I do not know for a fact - no chemical engineer here!

When my smog/air pump 'disappeared' (w/ the associated hoses and tubes), the cat's air tube stem was pinched closed and then bent over to prevent exhaust gases from coming out under the driver's seat. In addition to saving a couple of ponies from turning the air/smog pump, this also effectively stopped the backfiring when letting off the accelerator.

R/
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post #6 of (permalink) Old 09-06-2003, 01:27 AM Thread Starter
 
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Re: Air Tube & Cat. Conv.

Thanks for the advice guys. Seems like I also remeber hearing that the fresh air help the cat. work more efficiently. If I'm not going to hook the air tube up it is probably not worth having cats. at all.
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post #7 of (permalink) Old 09-06-2003, 09:01 AM
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Re: Air Tube & Cat. Conv.

Well, not necessarily. The earlier models did not have the air tube (additional fresh air) and still worked - probably just not as efficiently. But, if you are looking for justification to rid yourself of the cat, I'd say you are somewhat correct.
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post #8 of (permalink) Old 09-06-2003, 11:36 AM
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Re: Air Tube & Cat. Conv.

In my 87 it hooked up to a valve that let air from my air cleaner come into the cat. I understand this was to help burn off the fumes in the cat.or just add air so it seemed that the fumes out the tail pipe were not so bad. You know add good air to bad and the % of bad is not so bad! When the check valve failed and let hot air flow backward into my carb. I put my cat in a vice and pinched the line on the cat. shut! FIXED! [img]images/graemlins/grin.gif[/img]
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