question about smog..

vadim · Dec 3, 2008

Ok i have read on other forums that if you remove the smog pump from your system you'll fry the cats, i have a hard time getting my head arount this as this inlet for the smog pump is further down the exhuast system, near were the h pipe conection is. i could understand if it was ahead of the system. also my crown victoria never had a smog pump and rand the same type of cat setup. so i am just wondering how the removal of the smog pump can burn a cat out. i'm not trying to argue with anyone, just trying to understand the whole idea. thanks for any input.

NIKwoaC · Dec 3, 2008

First off, man, you ask a LOT of questions. You must have a new thread started in Tech every other hour or so! Haha, buy a few books, do some reading, you'll be caught up in no time.

Second, catalytic converters work by a chemical reaction that (in simplified terms) requires air and heat, among other things. Your smog system (Ford calls it the Thermactor system) uses the air pump to push extra air into the exhaust to help encourage the reaction. Depending on engine temperature (and maybe some other factors, I'm not sure) the air either gets injected into the exhaust right at the cylinder heads or through the pipe you're talking about, just upstream of the cats. SO that's not an inlet tube, but rather an injection tube. And yes, at least 2 of the cats are downstream of the tube (I believe stock 5.0s had 4 cats, but I can't remember now, its been too long since I ditched mine). Are you sure you know what cats look like?

Had to do it.

ANYWAY, if you remove the Thermactor system without removing your converters, they lose their effectiveness and I suppose that could lead to failure.

Don't know what to tell ya about the 'Vic.

68keyblr · Dec 4, 2008

I replaced my stock H-pipe with 4 cats with a new one with 2 modern cats that don't require the smog pump.

I ditched the smog pump and still sailed through emissions....and with a 331 no less

NIKwoaC · Dec 5, 2008

Yea, I looked it up after I posted because I wasn't sure about the 4 cat thing, so for a little more info...

There are two sets of cats on a stock Fox car, though the two pairs are not identical. The front two don't require the extra air to operate, but the back two do. As I understand it, one set of cats doesn't operate at peak efficiency until heated, so the other cats take responsibility of "cleaning" the emissions until the exhaust system temperature rises enough for the other set to operate fully, so there is a little bit of overlap in operation between the two sets. Either the aftermarket cats don't work fully during warm up, or the technology is different so that the air injection is just not necessary, I don't know.

gwiedner · Dec 5, 2008

The smog pump is required by the last two cats to work properly and they will burn up quicker without the air being pumped into them, at least thats what all the local exhaust shops around here told me, but as far as smog goes you may be able to put a set of cats and on pass emissions but you'll still fail the visual inspection without the pump.

vadim · Dec 5, 2008

ok, thanks guys, that helps. i only have 1 year left of emmision testing then i don't have to do it anymore, but i think i will go with the high flow cats that don't need a pump. i like to breath cleaner air if i can.

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