Removing secondary CATS

[goat]

Hi.
I have been thinking of removing the 2nd set of cats on the Cayenne. I was told that the car will still pass smog without them, and will be a little louder, which I want.
Anyone do this?
I am in California so I am a little worried.
Thanks any advice would be nice.
Tim

[Snipernick]

Holy smokes! Are there four cats on the Cayenne?

[goat]

Yep for of them.
Take a look at this site I think these make the best stuff and way cheaper than the others.

Porsche 955 Cayenne Turbo/Turbo S Bypass

[goat]

Ooops that is for the turbo try this one.

955 Cayenne S

[stealthn]

Yes I took mine off and put on Fabspeed cat bypass. You should not fail smog as the O2 sensors are upstream of the seconds cats, but you may fail visual. If someone sees them just point to the ones right off the headers.

The power is a bit better and the sound is nicer. I also added an EVO intake on mine and an IPD plenum which makes the sound really nice without changing out the whole exhaust.


Bob James

[goat]

Cool!
Going to go for it. Little worried about the whole having to hold up the tranny since you have to remove that cross brace.
Not too worried about visual, With all my previous & current cars they have never bothered to look under any of my cars.

[Snipernick]

I have not taken a look yet, but I'm assuming the upstream cats are identical to the downstream ones. If my hunch is correct, I like the idea of using the bypass pipes because it would preserve two cats in case the the other ones should fail.

[stealthn]

Different designs...


Bob

[Snipernick]

Ah...well there goes my practical idea.

[kennethg]

You dont have to remove the transmission crossmember. Rear of secondary cats has a slip clamp, just tap it back and they'll drop out. Hardest thing is the outer bolt on the passenger side pipe. S should be real close to my CTT. Took 45 min but i have a 4 post.

[goat]

Very cool stuff glad to hear of others wrenching and modding their Cayennes.
I have to take a look but if I remember the second cats are after the plastic shield or do I need to remove that too?

[stealthn]

I'm not sure what you mean by plastic?

I can't find my pictures or I would upload them. Jackup front end (or if you have air suspension put in terrain mode) remove plastic engine/underside covers, unbolt cats, remove from hanging mounts, put new ones on with gasket, tighten, test.

Pretty straight forward and don't forget a new gasket if going to stainless. I got extra rear clamps from Porsche and replaced those too just incase I broke a bolt while doing the install.

Have fun

Bob James

[goat]

Sorry meant the plastic engine/underside covers.
All and all pretty straight forward then.

Bob James Thanks Might be a weeks before all parts are here and am ready