Tatonka

Does anyone have AWE exhaust on their B7 RS4? What is your take on them? I was wondering if their Non-Res Cat-Back system with Downpipes would pass California emission. Or is just the Cat-Back system good enough. Thx!

spagolli94

This is on my wish list, especially because AWE is local for me. I have a buddy who has their non-res system with downpipes on is S5 (4.2). He loves it.

sakimano

Provided there are catalytic converters, and you take your car for emissions testing when it is nice and warmed up, you should be fine.

However if it is catless, that may prove a problem. It should be noted that by the letter of the law, California exhaust/emissions require NO modification to the exhaust or catalytic converters.

While I'm sure the exhaust sounds good, also pay attention to the diamter of the piping, the presence (or not) of a crossover (x-pipe is preferred for exhaust scavenging) and from the looks of testing and the fastest RS4s, a 2.75" diameter appears to be better than 2.35, 2.43 or 2.50. Basically the stock exhaust is 2.50" so you may be inclined to stick with stock at the end of the day or go 2.75" for performance gains.

The 2x catalytic converter per downpipe design is horrible...and that is where you should really focus your efforts to free up some horsepower. Elimination of the PRE-CATS (the set of catalytic converters closest to the engine) would be your best bet. You may need to make an adjustment to your oxygen sensors to pass emissions. You could also just look for a tune that eliminates the 'catalyst efficiency' CEL. This is not a primary control factor and is really there to notify you (or emissions) that the precats aren't working. Of course they're not...we cut them out lol.