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Cat delete

11K views 47 replies 13 participants last post by  Lakotiy 
#1 ·
Hey guys I will be removing my primary cats soon. Not replacing the whole header just removing the portion. Just wondering as to what I can expect from this performance wise. Any hp gains? How's it sound? Other benefits etc.
 
#47 ·
So gutting the primary cats and removing the secondaries is worth about a 40hp gain with a tune? Will this make the exhaust note sound strange having the larger open catalyst chambers vs straight pipe?

After reading this thread, I'm now going back and forth with gutting the primaries myself, just to keep from going through the lengthy process of removing the headers...however, I thought doing this would actually hurt performance, thus why a straight pipe is better?
 
#13 ·


I have done a lot of motor swaps, rebuilds, and tons of maintenance on cars but this mod has been by far the worst. The honey comb materiel is titanium, very light but very durable. You will not be able to bend the smallest piece by hand. It's very easy to do but PITA


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#16 ·
I may just do it myself. Need to figure out how easy it will be to do. Approximate time? And level of difficulty? I'm mechanically advanced for not being a mechanic lol. Is it a direct unbolt and then gut out of the inside then rebolt?


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#26 ·
Yeah I wanted to know if it is possible, in the location that the cats are to cut them out and just weld straight piping in its place! Please anyone?
 
#28 ·
So I can't cut the cats outs and replace it with straight pipes without removing the headers?
 
#41 ·
I honestly barely felt a difference from the secondary cat delete, I felt a much bigger difference from the eventuri intake, and full catless really stinks, my friend has evolve headers and secondaries deleted, thing stinks!!
 
#42 · (Edited)
How does the exhaust note change after removing the primary cats? Is it noticeably more raspy, or similar to stock but louder? (My M5's exhaust is currently stock except for a muffler delete.)

I ask because I switched my '04 Mustang Cobra from a catted X-pipe to a de-catted X-pipe with the intent of making the exhaust louder. The exhaust did get much louder, but in a crappy, raspy-sounding way. The exhaust noise coming up past the transmission tunnel now sounds louder than what's coming out the back of the car, and no, there is no exhaust leak. Fortunately, I still have the catted X-pipe and am going to swap back to it and just change out the mufflers (currently Flowmaster Super 40s) in search of something louder (probably Flowmaster 10s). I'd hate to butcher the M5's cats only to find that I hate how it sounds.

And, just to confirm, if I keep the secondary cats, the exhaust smell might be a little more than stock, but not bothersome (to most people)?
 
#43 ·
How does the exhaust note change after removing the primary cats? Is it noticeably more raspy, or similar to stock but louder? (My M5's exhaust is currently stock except for a muffler delete.)



I ask because I switched my '04 Mustang Cobra from a catted X-pipe to an de-catted X-pipe with the intent of making the exhaust louder. The exhaust did get much louder, but in a crappy, raspy-sounding way. The exhaust noise coming up past the transmission tunnel now sounds louder than what's coming out the back of the car, and no, there is no exhaust leak. Fortunately, I still have the catted X-pipe and am going to swap back to it and just change out the mufflers (currently Flowmaster Super 40s) in search of something louder (probably Flowmaster 10s). I'd hate to butcher the M5's cats only to find that I hate how it sounds.



And, just to confirm, if I keep the secondary cats, the exhaust smell might be a little more than stock, but not bothersome (to most people)?


Exhaust tone stays the same on this. Just gets about 20% louder. The smell gets pretty bad, I'm completely catless and sometimes on cold starts when I need to get something out of the trunk In the morning when warming up the car I can start coughing pretty bad. It's gets better when warmed up but still lol


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