sanadrustom

Hey Guys,

I'm pretty sure its the cats but just wanted to make sure before i go ahead and decide what i want to do with it. Last night i was well racing someone, and red-lined on 3rd gear. instantly i started to smell a strong sulphur smell. reason why i think its my cats is because when at idle i hear a rattle at times when i rev the car a bit(no heat shields, i removed them already). my question is if i decide to remove them (if they need to be removed) is it better to keep them dual pipes to the muffler? or should i just have one blocked off and go one pipe straight to the muffler?

curious if there is any gains or draw backs from doing either or

Thanks

UrS4boy

Sulphur smell starts with using a cheap grade of fuel. Change that.

If you removed the factory shielding between the cats and the body, you are asking for a fire or at least a much hotter than needed interior floor.

Removing the cats is potentially illegal.

Properly operating cats do not negatively impact engine performance.

There are aftermarket exhaust systems with cats, e.g. Stromung, that use a single, non-branching down pipe and a single sport cat. However, you should not just block off one pipe of the stock system, you need both pipes in operation so as to NOT impact performance.

Here is a photo of Dan T's (Ringbearer's) old OE AAN downpipe "Y" and catalytic converters showing the last reminant of the OE insulation cover on the down pipe (which is fine):

<img src="http://12v.org/urs/RingBearerDanTsOldOEExhaustY.jpg">

Here is some C4 AAN middle and final exhaust system info:

<img src="http://12v.org/urs/AANWasteGateExhaustPipeAndBoltsPNs.jpg">

<img src="http://12v.org/urs/C4UrScentreAndRearExhaust.jpg">

Here is one photo of the stock C4 AAN exhaust system:

<img src="http://12v.org/urs/OEUrS4ExhaustDustovich_Small.jpg">
Photo courtesy of Dustovich in Edmonton, Alberta.

sanadrustom

thanks Dave,

its same grade gas i use in my allroad and never had an issue with it, i use either petro ultra 94 or shell vpower(best two options here in Calgary). i understand the removing of the cats is illegal, but what other option do i have.

i have had them removed previously on my other Urs6 that i used to have and the car ran okay but i might remove the silencer as well this time if i decide on that's the way i want to go.

do you think this might be a running rich/lean issue that is also the cause of my miss fire?

UrS4boy

WHaaat!!? You're in Calgary? Have I got you on the BC/Alta/Sask Ur-S email list? Are you aware of S-Fest West out here in the Vancouver area, starting tomorrow?

Alberta probably doesn't care about auto emissions because of all the coal-fired power plants and the oil sands industries so decatting would probably never be found. That said, personally, being an environmental engineer, I would find a good set of used UrS4/S6 replacement cats and have them installed.

I wouldn't remove the silencer. No real gains, just highway droning pains.

Misfire is either dirty injectors (which could be caused by bad fuel/bad fuel filter) or ignition problems.

Try running injector cleaner through a few tanks of fuel.

As for the ignition, it could be anything from the plugs, to the connector boots, to the coils to the power output stages.

Click on THIS for a good read.

sanadrustom

I do have the 1.8t conversion kit in the car. Injectors can be the biggest culprit cause god knows who had it if they ever used proper fuel