05VENOM

Had the E63 up on the rhinos today and was checking out the underside of the car. There seems to be two cats right past the exhaust manifold then two more cats just upstream from there (there is a crossover pipe just before the second cats...for what??) then the resonator and finally out the mufflers.
Seems pretty restrictive. Questions are:
1. What is the purpose of the resonator (is it as obvious as the word itself)?
2. I want to remove it (purely for the sound) there seems to be a flange before and aft...does this mean new pipes(x-pipe??)would be a slip fit or do they need to be welded?
3. What are the consequences if I remove the second pair of cats (keep in mind this is a daily driver and must pass NY emissions)

Thanks for the help.....Chris

BiTurboAmg

I dont know about the resonaters but I know on my e55 when we added the kleemann headers we deleted the first set of cats and just used some down pipes. From what I understand you will gain some hp but you have to code the ecu or you will get a cel due to the missing cats. I know some guys run 02 simulators and a few other things but I just had kleemann redo the ecu so the car would think they are still there and that worked just fine. Search the e55 thread for resonator delete I know it has been done and talked about a few times. Good luck!

chiromikey

yes, the resonator does exactly that...just helps fine tune the exhaust note. on the 55 there's not much to be gained in performance or sound by removing it by itself. you shouldn't have a problem removing the secondary cats as the o2 sensors measure the difference pre and post primary cat but i wouldn't want to mess with emission laws in some states. removing both may give you a slightly more aggressive sound but it won't be until you replace the rear mufflers that you'll hear a significant difference and i'd bet it won't be until you replace the entire system that you'll see any real performance gains.