Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Why does it do this

when i have my Superchip on and im running 93 octane gas i get no sulfer smell(Rotten Egg). My chip has been giveing my problems so i took it out and im running 89 now and the sulfer smell came back. Anyone know why this is, Should i just stick with 93 even though i dont got the chip in.

hmmm...sulfer smell is usually from a dying (or dead) cat. maybe the chip is giving you better burn and therefore putting less stress on your cat, and therefore less sulfer stink.
Can't say that's why for sure, but just thought I'd throw an idea out.

I think that lower octane gas inherently has more sulfer in it.

Sulfur smell is not from a dying cat -- there's no sulfur in the catalyst. It's from higher sulfur content in the gas and likely a rich burn condition.

Your chip might have some fuel trimmed out and without it you're burning more rich.

-Lance

Originally posted by lkinley:

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Sulfur smell is not from a dying cat -- there's no sulfur in the catalyst. It's from higher sulfur content in the gas and likely a rich burn condition.

Your chip might have some fuel trimmed out and without it you're burning more rich.

-Lance

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I know there's no sulfur in the cat, but I always thought the sulfer smell was a symptom of a dying cat. I've been wrong before, though.

Originally posted by Derk2000:

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I know there's no sulfur in the cat, but I always thought the sulfer smell was a symptom of a dying cat. I've been wrong before, though.

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So why would it be a symptom?

If the cat is dying, that means the catalyst is decaying -- the platinum-based matrix is no longer working. So why would this cause a sulfur smell?

If you are burning rich enough, a lot of raw gas will hitting the cat, causing high temps in the cat as it burns the fuel. This happening over extended periods can cause the cat to decay. It may be a symptom in that it is the CAUSE.

-Lance

Thanks for shareing your thoughts guys. Im not sure im running Rich though. I know im running real lean from both my dynos. Guess i will try putting 93 back in even thought i dont have the chip in.

The sulfur smell CAN be connected to a catalytic convertor problem. Cats don't always decay and crumble quicky, but can become clogged with soot and in our car, the main cat can certainly become clogged with parts of a decaying precat.

The sulfur that causes the "rotten egg" smell does not originate in the cat, but can collect in the cat as fuel with high sulfur content is burned or deposited unburned into the exhaust.

The biggest evidence of this being true is the many many people, including me, who have eliminated the sulfur smell by getting rid of their sulfur enriched catalytic convertor either through removal or replacement.

I have no idea why this would be different with or without the superchip, but the idea that the higher grade gas has less sulfur to be deposited into the catalyst is probably true.

I-Dom-In-8 : what kind of exhaust mods do you have?

I have a Dynomax ultra flow in place of my res and a magnaflow muffler out back.

I would also check for leaks near the front of your exhast. I no longer get a sulfer smell (cat free me), but I have a very small leak at the rear manifold that allows me to smell exhaust when I get on it hard. You can see where exhaust was getting out of the y-pipe to manifold interface on my old y-pipe too so I would suspect that this also contributed to the sulfur smell in the cabin.

I would see about getting a new cat or y-pipe. I'm pretty happy with my yo-dude pipe, but it was a huge pain in the nutz to fit. Good luck.