Gammaz113

Hi All,

I deleted my secondary CAT today and replaced with straight pipe at my local exhaust shop. I noticed rotten egg smell inside cabin after hard acceleration and race start. Under normal driving is fine. Is it normal to get rotten egg smell after hard acceleration without 2nd CAT?

roadkillrob

I never had any smells at all with secondary cat delete - it would be normal if you had no cats - do you still have the primary cats? Do you have a tune?

Ludedude

Gammaz113

No tune. Still have primary cats. Only under hard acceleration or race start. I will bring it back to the shop to check.

Gammaz113

​​​​​What are the sign and symptoms of a leak near 2nd cat area?

curt.r

SuckaGDog

What year and how many miles on the car? It's normal for that egg smell to occur after hard acceleration or pulls. It's only a problem if it smells constantly like that. Which would mean the primary cats are failing.

The sole purpose of the secondary cats is to filter what the primaries left behind. I'm sure it removed a majority of the smell before.

Doc Oc

​​​​​​
Put the car on a rack or stands and run your hands just above and all around the welds with the car running. You'll feel the leak if there is one. I do this type of work daily and it's very hard to get a clean weld at the top of the pipes (assuming they didn't take the pipes off to do the work) due to space restrictions so if there is a leak it's probably at the top of one of the welds.

bhamg

I'm fully catted and get the rotten egg smell after hard acceleration. It comes with the territory.

AhhMyyGawd

its normal, should go away after a few more hard accelerations. Its the heat expansion or something that will cause that smell. Give it a few days, info is from Mike

Jasonoff

You need to let your primary cats heat up more before beating on it.

BalanBro

Mine does it too under heavy load conditions only. Good to see it's relatively common, although I still find it strange. I've driven many different cars from N/A to forced induction and various flavors of OEM cats, high flow cats and test pipes, and I've never had this sulfur odor before. For the folks that do have this smell, are you running a tune (I have EC V7)? I'm thinking WOT AFRs may be a factor.

Gammaz113

My rotten egg smell for somehow has disappeared even under short burst of hard acceleration and running at highway. I am taking my beast out in the track in a few weeks time and will see how it goes.

I am really impressed with 2nd cat delete! it brings the beast alive! loving the AMG Music

sventastic82

The rotter egg smell is usually caused by worn cam shafts. I would ask a euro car specialist to fix that.