Why does it do this - CEG Archives

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:
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

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:
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.

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.

Try a differant brand of gas. This can help.

When I had my sulphur smell, it was due to a bad O2 sensor. Changing it fixed it. You case is interesting though....

For all who are interested. Sulfur (in gasoline) that burns in combustion produces SO2 (sulfur dioxide) which in water becomes H2SO4 i.e sufuric acid. No rotten egg smell.
Sulfur in gas that makes its way to cats in raw gas is catalyzed to H2S hydrogen sulfide and eventually to oxide form if cat can handle volume and has an O2 supply. Thus rotten egg smell may be combination of a too rich an air fuel mixture , higher sulfur content and possibly low efficiency cats. Ford would like to blame oil companies (they do) but I think they designed emmissions system too close to limits. Notice that usually rotten egg smell is present when pushing hard with acceleration not when driving sedately. Thus even if O2 sensors are not showing any problems themselves or any cat efficiency issues it could still be an O2 sensor but my bet is on marginal programming within Ford's engine management system which interprets the O2 sensor readings and adjusts the air fuel mixture. Probably keeps it near rich.
Also notice how often you notice the problem from other cars and judge where problem is accordingly.
Here is Canada Ford may have issue with the use of MMT as an octane booster (thanks Ethyl Corp) since it does interfere with sensors (and is a neurotoxin to boot) but that is another issue. However it does contribute to the problem.

it means your car is running a little rich, or your not firing all 6 cylinders which is doubtful if your not witnesssing other problem like your engine running rough. it doesnt burn all the fuel. and your catalytc converter converts it in to that suffer smell, type of chit.

wow, this all from the knowledge i gained on ceg. this sites great.

Originally posted by lkinley:
It may be a symptom in that it is the CAUSE.

-Lance

I see what you're saying. I never knew the cause of the sulfer smell, I just always associated it w/ bad cat. This thread is interesting...learning a lot.

Originally posted by dellowm:
For all who are interested. Sulfur (in gasoline) that burns in combustion produces SO2 (sulfur dioxide) which in water becomes H2SO4 i.e sufuric acid. No rotten egg smell.
Sulfur in gas that makes its way to cats in raw gas is catalyzed to H2S hydrogen sulfide and eventually to oxide form if cat can handle volume and has an O2 supply. Thus rotten egg smell may be combination of a too rich an air fuel mixture , higher sulfur content and possibly low efficiency cats.

This is interesting, I'm a freshman in college and going into engineering so I am just learning the details of this very process in Chem 115. It's a bit daunting to look at some of this stuff, gotta work my way up the food chain of education...