Long story short I just recently bought an 99 A4 APR stage 3 that wont pass smog. I figured I would do a boost leak test and replace the CAT/Down-pipe just to cover all my bases. Well I just got done taking it off which was a major pain in the *** to find out that there's nothing in it at all, just straight pipe. Is this how its supposed to be? I always was under the impressions that there was two CATS, one leaving the turbo and another mid exhaust.

 

my A4 has only a single cat, immediately after the turbo. my S4 has (had anyway) two cats on each side, a pre-cat and a main cat. i wonder why they are different?

 

I'm Pretty sure that when I had my car smogged the guy said he was looking for two CAT's. I wonder how many I need to pass visual? Or can I leave the APR Cat/ test pipe and just replace the midline one...

 

a cat is suppose to have many cells in it. if yours was empy, then it isnt a highflow cat. its just a pipe. you need to let us know why you failed smog, sniffer tet, obd readines, visual inspection.... your a4 only had one cat stock, so that should be all you need to pass visual inspection. 2.8 v6' have two cats. im guessing you failed the sniffer test, in which case you will need to put some sort of cat in

 

There's no "mid-cat" on a B5 1.8T. The OEM catalytic converter is, as stated, directly downstream of the turbo. It's actually pretty easy to get to once you get the airbox off. The best way to get it out is to unbolt the forward flange from the turbine housing, then crawl under the car and unbolt the clamp that joins the downpipe with the rest of the exhaust, then yank the whole mess out the top of the engine bay (after disconnecting both O2 sensors). The other can you're referring to is the OEM resonator.

Redline is right, you need to get a print out from the shop that failed you to see why you failed. If you're in CA, most HFC's will fail anyway...

 

Update. All high flow catalytic converters or replacements will fail in California unless there CARB approved. The emissions part has nothing to do with the visual. This really sucks for me because I dropped 450 bucks on a HFC that I had 034 fabricate for me. The funny thing is that my emissions now are way under the limit and even the average for California. This has to be be one of the most dumbest laws out there! Now my only option is to either pay someone off, which is a lot harder than it would seem or to buy a donor car and return my car back to stock. If I had to do it all over again I would probably purchase a CARB legal CAT and have that modified to fit my specific application so I would still have the CARB numbers. Lesson learned. If anybody know a smog shop in northern California that doesnt give a **** about the visual inspection please PM me.

 

New HFC

Pre installation

After install