What do you think an aging catalytic converter would do to gas mileage numbers?

 

I'd worry more about pre-cat's vs the main cat.

 

thanks man, this thread was actually meant to be a a poll.


Would you change your cat(s) if you had no codes associated with the cat(s), but smelled the "rotten eggs" after at spirited accelerations, and not typically around town and normal conditions.

 

If my cat smelled like rotten eggs, I'd probably just bathe it...

 

I would change it since Cattman's fast cat is relatively cheap vs OEM. And it's design is really good for flow, from its shape to it's diameter.

Mine even gives a slight rotten egg smell (sulfur) when I get on it every now and then, not bad but noticeable.

 

Then add a poll.

I would, yes.

Junk in the pre-cats... isn't that the primary cause of the 1500-2000 rev "bees-in-the-can" syndrome? I've had that noise for about a year now. Very disconcerting. No cel, no smell, and no (perceivable) power loss, just bees in a can.

 

Interesting and comforting to know you experience the same, and my only question with the Cattmans fast cat is Wouldn't you need to deal with all the o2 sensor crap after going aftermarket on that component?

Thanks for the reply,

 

You wont need to relocate the O2 for a main cat swap.

 

What O2 sensor crap? There is no O2 sensor behind the main cat on 02+ models. Also, it's a real converter, not a BS resonated straight pipe like the Megan type.

 

Hmmm... SOMEONE (psst: that's you) haven't been reading all the dramatic pre-cat threads that have been cropping up like maggots in rotten meat. The (non-specific, generic) pre-cat has that honey-combed piece of metal in it that the substrate dwells on. The metal ages and begins to flop around, hence your bees in a can sound. Apt name, given the internal structure. I can't remember the exact shape and stuff of the Maxima pre-cat internal, but it does the same thing. In the worst case scenario, that metal works itself loose, or enough of the substrate loose, and gets sucked into your main cat, which promptly plugs up and stops your engine from running 'cause the exhaust gas can no longer leave the cylinders. Oops. Child of Korn will readily describe his cat-clogging experience, if you want to get dramatic about it.

NMex's comment is referring to the debated "pre-cat dissolves backwards into your engine and you lose it forever so sad bye bye" issue, which he comes down on both sides, depending on the relative humidity of New Mexico's steppes.

I can smell a gas-y smell after romping on mine, but I've never smelled sulfur from any part of the exhaust system. Trace exhaust leak causing the gasoline smell, mayhaps?

 

Aw, crap. I need to start reading up on this in a more focused manner. For the last year or so, I've been just randomly paying attention to it and ruling out things like gas, timing, pinging, etc.

Thank you, Eirik. So we don't throw Prophecy's thread OT, please PM me if you have links and info handy on resolving the bees-in-a-can with my '03 (Cattman Y-pipe, OEM cat, Cattman cat-back).

Or post it up here if you think the OP would benefit. Either way.

Hmm... each pre-cat on the 2003 lists for $625 at Courtsy Parts. That's nuts.

 

^ Time for OBX Headers.

 

Bosal / Eastern, etc.

 

There is a guy at my dads work who is replacing a motor in a 02 maxima cause the pre-cat went bad and sucked that shti back into the motor and killed it.... Im throwing a P0430 code so im trying to figure out if its an O2 or cat.... >:-(

 

Approx half the price of OEM, but still more $$$ than headers when replacing both front pre-cats. And gutting doesn't seem the right option.

Damn it. This was not on my mind when I got in the car today.

 

to get back a little, to try and achieve better milage...

Have you checked PCV? I swapped mine and noticed about a 2mpg gain, as far as the cat- when in doubt change it.

 

Getting the same one but think mine is due to the o2 sensors the 430 is for the rear bank right or no....

 

Doesn't the Cattman y pipe for the 02-03 eliminate the rear cat so you would only need a front one.....or might be for the 00-01 not sure......

 

No. The 5.5 gen Cattman-Y is a direct y-pipe replacement, bolting to the two pre-cats that hang off the exhaust manifold, and then to the main cat in the rear. It's an upgrade over stock because of the clean bends and the uneven length collectors. Headers use the space of the deleted pre-cats for the extended collectors, one for each port (duh, right?) The lack of pre-cats is why most of the time people need an O2 simulator. That's been my understanding of the tech all along... someone feel free to correct me if I'm off-base.

Here's the diagram of OEM config from CourtesyParts that I'm sure most 5.5 gen owners have seen a bazillion times:

 

I'm not sure how to take being mentioned LOL. No dramatization there. It ruined the engine and clogged the main cat. Gut them or get headers and test pipe. F cats. I'd saw the pos off at the dealer if i ever bought a car new

Op: I'd replace it with a fast cat or just hollow it. It's a very unnecessary part and then you won't smell light rotten eggs.

 

Well my bad but I know he designed one like that but maybe it was the Cali Spec or Fed Spec....

 

What about the rumors on the internet where the broken pre-cat gets sucked in the engine via exhaust valve (how can that happen???) resulting in scored cylinder walls and huge oil consumption??????

 

lol, or Hotshot, or maybe Cattman...

 

Good luck finding Hotshots

 

O.k so I'm not gonna read through this whole thread... is it really about the man cats or the precats?