I plan on replacing my two original cats with one three-way high flow cat. I was wondering if this will have any affect on the operation of the air/smog pump.

I know that it will still work as long as the motor is turning it and it will still perform it's function during warm up. But will it still be useful after the warm up phase with a catalytic converter that does not require the added air to catalize the vapors?

Also, just out of curiousity, what is the purpose of the air tube that some after market cats have? Is that supposed to be similar to function of the smog pump after warm up?

 

Depends on the chemistry of the new cat. If it contains Selenium (oxygen-storage), then you don't need any 2ndry air. Read this: Emissions Systems. Replacement cats with an air tube need 2ndry air.

 

Thanks for the article, it was very informative . As far as selenium goes, I'm not sure how to find that out. I've been looking at the Magnaflow universal cats; some are 3-way and some are 3-way with air.

I pulled this quote from the article:

Over time, the cost of producing catalytic converters has come down, and the quality of their construction has gone up, making them very reliable & effective. So effective, in fact, that most now don't require the addition of downstream air. They have also been improved with additional catalyst chemicals that reduce CO & NOx emissions (3-way cats).

Does this mean if I get a 3-way Magnaflow converter there is a chance that it won't need the air pump (again, I'm sure sure about the selenium part)?

 

If the high flow converter has the air tube, you need the pump. If it doesn't have the air tube you don't need the pump (although you may still need it if you want to keep the rest of the air injection system.) However, depending on your local laws, you may need the pump in place simply to pass your vehicle inspection.

 

Thanks. I just checked the emission laws for my county in PA and it says specifically that the air pump must be present and can not be tampered with. I think I'll get a Magnaflow Y-pipe with a Magnaflow cat (with the air tube). Do you think a local shop could make a hole in the Y-pipe for the tube that goes into the exhaust from the air pump?

 

There is no tube that goes into the exhaust from the air pump. The outlet of the air pump goes either to the secondary air system in the heads or to the tube in the converter.

 

If you get a non-air cat, just disconnect the rubber hose behind the engine from the metal downpipe at the check valve; delete the downpipe & check valve. Any shop that can install the cat can handle this for you, leaving the air pump & all its visible plumbing intact.

 

There is a pipe that comes down into the exhaust just after the first cat, it's coming from above the cat but I can't tell where it goes from there. Any ideas as to what that is?

 

That tube is the same as the tube that goes into a single 3-way cat.

 

I bought a second belt (88.75) to use for bypassing the air pump. I tried to put it on today and, although it fit all the other pulleys, it still rubbed the air pump enough to turn it. Is there some kind of trick to this? Is there a way to loosen the air pump or take off the pulley while still leaving the pump on the motor?

 

If the law says you need the pump anyway, why should you care?

 

It's really only for an experiment, I plan on returning the belt and running the air pump with the stock belt. I've been having a lot of trouble with an erradic idle ("Wandering Idle" thread) and I've gotten a few suggestions that the problem could be with parts of the secondary air system. I haven't been able to see anything visibly wrong with those parts thus far, but I've tried just about everything else, so I thought I'd see what happened to the idle when the engine was running without the air pump turning.

 

If I do this do I have to make sure the pump is not turning? I wasn't able to get the bypass set-up to work so I wonder what the function of the pump would be without the downpipe.

 

No, leave everything else as-is. Just let that rubber hose vent.

 

I am going to take Steve's suggestion and delete the air system at the check valve. I was getting ready to order this magnaflow kit off eBay when I noticed that, since it's a direct fit setup, the cat comes with the air tube. I asked a couple of stores that sell that product if they could switch the converters to a non air tube model and they all said that I could just weld the air tube shut and it would be the same thing. Is that right?

http://cgi.ebay.com/ebaymotors/ws/eB...TQ:MOTORS:1123