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catalytic converter to lessen exhaust smell in cabin?


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Has anyone installed a cat for the purpose of helping cabin smell, and did it work? I've read the numerous threads on this issue and have made a list of fixes to apply, but Im specifically wondering if a cat-con makes a substantial difference in exhaust smell?

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With a properly sealed exhaust system you shouldn't have ANY smell in the cockpit. Fix your leak(s) instead. Put a new seal on your rear hatch, if necessary.

If you just slap a catalytic converter (hereafter: cat) onto a vehicle not designed to have one, here's what'll happen.

For a month or so it's gonna work great. It'll convert CO to C02 and N0 to N02. You wont' see black smoke or smell a thing.

Then at some point it's either going to plug up with carbon (from running slightly rich) or else the core / pellets will melt down from running lean, and the slag may completely block your exhaust flow.

That's why cars with cats have 02 sensors; to keep the fuel mixture (rich/lean) within a very narrow range to prevent damage to the cat. Some will intentionally run lean awhile, to accumulate oxygen in a 3-way cat, then utilize that stored 02 to "clean up" a rich mixture when accelerating hard, etc. The type of cat you have - 2way, 3-way, oxidizing, reducing...DEPENDS on the software programmed into the ECM. The two work in harmony, or are SUPPOSED to.

This is one reason why AFTERMARKET cats so often fail when installed in OEM applications. Or only keep the check engine light off for a short time before it comes back on.

Yes, there were a few early vehicles fitted with cats without 02 sensors. And no, they probably didn't last very long, and they were also probably of a very specific design, open flow, intended to accept mixture extremes.

So in a word, FUGGEDABOUDIT! Fix your manifold or exhaust leak and quit gassing yourself!

Edited by Wade Nelson
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The OP is talking about fumes from the tail pipe getting in to the cabin, I believe. It's a big problem with the S30's, maybe not so much with the S130's.

It is possible to find all of the various leaks in the back of the car and fix them to keep the fumes out. It take some work though. A big leak area, for my car anyway, seemed to be the vinyl covered access board that covers the bottom of the inside of the hatch. There are small weep holes in the hatch, plus the big holes covered with rubber plugs, that can let fumes in to the internal structure of the hatch, and then through the access cover on the inside to the cabin. I took extra care to seal that with weatherstripping, and also to make sure the hatch itself seals tightly to the body. Other things to look at are the foam seals around the tail-light assembly, the access hole grommets for the various tubes and wires and any rusted out areas, like the bottom of the spare tire well. With the windows open or even just air passing over any holes on the sides of the car, the pressure inside the cabin gets lowered and the fumes that collect behind the car get pushed in through any tiny holes.

I don't even smell fumes any more, unless I am stopped and get a whiff through the fresh air vents. The fumes while driving smell is gone.

To Wade's point though, a cat with out an O2 sensor will probably not last long.

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Thanks guys, fair points about the cat not lasting long without an o2 sensor setup! That hadn't occurred to me.

I've compiled a list of various spots to examine and fix in attempt to stop the smell. Previous threads have been helpful.

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