Catalytic Converter Question

[Old77]

I'm pricing Catalytic Converters and I'm seeing with and some without air tubes. What are the air tubes for? How do I know if I have to have one?

 

[Georgeb]

I believe the tubes are for air injection. Not sure if any squares ever had air i jected into the cats or not.

 

[skysurfer]

Nah, air injection and cats are two different things. Never heard of air tubes on cats, got a link?

 

[Old77]

Nah, air injection and cats are two different things. Never heard of air tubes on cats, got a link?

Yeah just a sec....I first came across it on Rock Auto

 

[Old77]

Here's a screenshot. Hard to get links from Rock Auto searches

You must be registered for see images attach

 

[Georgeb]

Nah, air injection and cats are two different things. Never heard of air tubes on cats, got a link?

Ford did it on their cars trucks and vans in the 80s'

 

[bucket]

Nah, air injection and cats are two different things. Never heard of air tubes on cats, got a link?

Third gen F-bodies had an AIR injection tube into the converter. Can't remember if my 84's did, but I know all my '85 and later TPI cars did. Can't recall if my '92 RS had one.

 

[CorvairGeek]

The air injection tube is for three way catalyst, which I don't believe any 49 state squarebodies used (can't say for sure for Cali). The rear bed of 3 way catalyst uses platinum, palladium, and rhodium to break down NOx emissions (besides CO & HC), some applications required more oxygen for the process, thus an air injection point. GM cars used them more during the 80s with the monolithic catalyst and the tighter tail pipe (and mileage) standard for cars. Controlling NOx emissions at the catalyst can be more efficient than controlling it in the combustion process. The efficiency of fuel injection alone just about (if not entirely) eliminated the need for the catalyst air injection point in GM products.

 

[Old77]

Wow! Thank you @CorvairGeek awesome info

 

[skysurfer]

That's interesting. Never seen that type of cat but was wondering why some emissions stickers call out twc (three way cat) instead of most that just say cat. It figures I'm not up to speed, I did my last smog inspection about half-way through the squarebody run before this type of converter came into use.

 

[Old77]

That's interesting. Never seen that type of cat but was wondering why some emissions stickers call out twc (three way cat) instead of most that just say cat. It figures I'm not up to speed, I did my last smog inspection about half-way through the squarebody run before this type of converter came into use.

Yeah, it's weird LOL I just went ahead and ordered that one at the top of the list for $40. I should have new exhaust on the '87 soon

 

[skysurfer]

The air injection tube is for three way catalyst, which I don't believe any 49 state squarebodies used (can't say for sure for Cali).

Bouncing between this thread and tuberbob's smog parts thread. He posted a pic of his emissions sticker that doesn't specify it's a California vehicle but it does call for a twc. Seems like the only consistant thing with emissions equipment is that it's confusing.

 

[Georgeb]

I wonder if because of the A.I.R systems on our trucks that connect to the manifolds is what feeds the extra 02 to the three way cats rather than a tube run down to the cat itself????

 

[skysurfer]

Tuberbob's thread has pics of two emissions stickers that call for a twc, but only one calls for air injection. I'm wondering if the tubes on the cat are just open to ambient air and draw in the same way siphon-feed sand blasters do. If the tubes face forward they would get fouled by road debris but if they faced they rear they could still draw air but not garbage off the road.

 

[89Suburban]

Good thread.