I removed the cat yesterday and put in a custom test pipe I welded up. Wondering what that metal tube coming off the cat does that goes up to a rubber hose does. I just unbolted it from up there and don't notice any difference.

 

in certain conditions the air pump air comes thru that pipe into the main cat, mostly @cruise and decel. its pretty insignificant in the scheme of things anyways, and you have no cat, so its double useless.

keep it though, cause they aren't available new, and most junkyards throw that pipe away with the cats

 

The air pump sends air through it to cool off the catalytic converter. Otherwise the catalytic converter would heat up and the insides would burn out of it, or else it would start of fire. Hard to say really. It's supposedly to keep the cat from overheating though. You don't need it anymore. I trash mine always, because I will never put a catalytic converter on.

 

that is incorrect. http://www.jimrothe.com/mazda/84_tra...raining_4a.pdf

 

Yeah thanks guys I figured it was that air pump line to the cat. I just removed it from where the rubber line hooks up, so I can put it on again in two years...

Thanks I now have headers, custom test pipe, and a Holley 465, on my "CA" 12A. LOL.

 

Sorry but you are incorrect.

The air pump system is there to actually help "Heat" up the cat so that it gets rid of the unburned fuel. Think of it like a bellows like they used back in the old days at a blacksmith shop. It made the heat hotter!

That is why when you remove the Air pump that you don't want to run a catalytic converter because all that unburned fuel eats away at the internal materials of the catalytic converter until it comes apart inside and clogs your exhaust system.

 

Wow, I stand corrected! I've been misunderstanding that whole system for a long time now. Thanks for the info fellas.

Jamie

 

that book is very cool! if they had just thrown that in the passenger seat in every car, there would probably be a lot more around