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.
Do it, with the stock headers and primary cats gone, youll have an amplified F1 sound, delete secondary too, use a 3 inch x pipe, 3.5 inch tips. Believe me its going to be music. About 30hp gain.
make sure to get a tune to help with the reduced back pressure - no cats on primary and secondary with a tune will give you 550 to 560 HP using OEM manifolds with a tune.
I have an unused FAM tune for NA that i am thinking about selling -
Primary gutted has increased 40hp proven on a dyno. There's was a base dyno and after mod dyno. The post is on here somewhere. But from experience, I got my cats removed last week and the difference is huge. You have to get the secondary removed as well and have your 02 sensors coded out
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?
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
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?
Not true. Removal/installation of headers is about 10 hours, than you have to cut open, gut it and weld it back up. That's 13 hours of work compared to gutting them installed that takes 4 hours
I have a guy at work telling me not to because then back pressure will cause problems without a tune. I didn't plan on doing the tune for a few months. Any thoughts?
I wonder if just gutting the stock primaries actually creates issues with exhaust flow since there is now an open chamber. Probably better to just cut them off and install a straight pipe.
I'm not a welder but I'm sure you can't get a weld all around the test pipe. That cat is exposed because the subframe or steering rack is removed I believe.
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!!
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)?
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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