E63 Long Tube & Cats Question
Today I saw an E55 guy ran his long tubes to the secondary cats. This was a high 10 second car on sticky tires. I assumed they were a 600-800 cell cat. I know they are a different material then the primary cats internally. Any one have any input on this? I wouldn't mind saving a couple hundred bucks and the time welding in the Vibrant cats if the stock secondaries are not as restrictive as I'm thinking they are. Going catless is not an option. I can't stand the smell.
Any feedback is appreciated.
Last edited by layzie12g; Apr 8, 2015 at 10:04 PM.
Really though... That would be like me asking them to move you and your CLK with quad exhaust to the CLK with part of the forum. That is the first douche thing I have ever seen anyone post in response to any of my threads on this forum.
Last edited by layzie12g; Apr 8, 2015 at 09:44 PM.




My "through" I meant the exhaust flow from the headers are being ran through a restrictive stock catalyst. I'm basically asking if anyone has any numbers with stock secondaries vs aftermarket cats vs catless. I know catless with all ways make more power. I gutted the cats on my CL. Both the primary and secondary catalyst materials where DENSE.
If I'm going to be shorting myself 10 horsepower between 200 cell cats and the O.E.M. secondaries I won't mind buying race cats and welding them in. I think your saying you run aftermarket cats after the collector as a primary cat so the 02 sensors reading a functioning cat.
Last edited by layzie12g; Apr 8, 2015 at 10:20 PM.




Sorry no HP numbers so I cannot help with that. I did read a post ages ago about a guy from California that had Cali legal cats installed in the MBH system and it cost him 20 whp. I don't know how many cell the cats were but maybe Mike might remember. That might give you a reference for stock secondaries vs 200 cell cats.
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Your exhaust will only smell of gas upon initial startup. It will go away once the engine is warmed up. I currently run the ARH headers with 200 cell metallic cats and xpipe.




