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Discussion Starter #1
Hi, new member here. Just wondering if many members have removed the cat and retained the original muffler. My thinking here is that I like the looks of the stock muffler and really don’t want a lot more sound. I just like the idea of loosing 10 pounds or so of useless weight. If I do remove the catalytic converter it would be a winter project along with snorkel removal and ecu reflash. Any experiences and opinions are welcome. By the way great site and a lot of great posts as I have lurked for a while. The bike is a 2020 monster energy edition and I am very happy with it so far. I sold a KTM rc390 a couple years ago because I never liked the engine It always seemed flat and not a lot of fun to run through the revs.
 

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My thinking here is that I like the looks of the stock muffler and really don’t want a lot more sound.
Welcome!

You're gonna get a lot more sound if you remove the cat, regardless of what muffler/slip on you have.
 

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Thanks for the reply dread. Are you basing that on the fact that the cat obviously does suppress a lot of sound? Which I agree removal will increase sound to some degree. Or have you actually heard an r3 with the stock muffler and no cat? No try to be argumentative Just looking for firsthand feedback on what to expect for sound increase. I know I am a little out of the norm hear in hoping for less noise not more.
 

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I'm mostly basing it off the fact that the exhaust sound barely changes if you take the muffler off as the cat is doing 99.9% of the sound deadening. Adding a slip on without removing the cat merely "trumpets" the sounds so it's a little louder.

So I'm ass u ming after removing the cat, the stock muffler won't do much to muffle the sound. It'll certainly be quieter than a full after market exhaust as the pipe diameter is smaller.

I also saw a listing of an R3 with a cat delete and stock muffler on TradeMe (NZ version of ebay) a while back and I out of curiosity I asked if he had an aftermarket tune done. The seller responded saying that apart from the popping when the revs decrease and it being obnoxiously loud, he didn't think it needed one. 😅
 

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Discussion Starter #6
I think the lean popping on deceleration and “obnoxiously loud” are pretty clear signs that the cat is doing a lot of sound deadening and providing a lot of back pressure as well. Kind of to bad for my hopes of just removing it to save weight and not change sound or fueling much.
 

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Removing the cat and retaining the stock muffler would make your bike about 80% as loud as a full exhaust system from Akrapovic, or Yoshimura. I have a slip-on exhaust, and my bike is only barely louder, but does sound much better. It changed the exhaust note, rather than amplify the volume.
 

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Discussion Starter #8
Thanks for all the replies, it is pretty obvious that the cat/muffler is responsible for a lot of sound suppression. I even found an old thread were a lot of people tried a lot of different combos and each one found what you guys are saying to be true. As much as I would like to shed dead weight the thought of increasing the noise substantially makes it a no go for me.
 

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Thanks for all the replies, it is pretty obvious that the cat/muffler is responsible for a lot of sound suppression. I even found an old thread were a lot of people tried a lot of different combos and each one found what you guys are saying to be true. As much as I would like to shed dead weight the thought of increasing the noise substantially makes it a no go for me.
Hmm... increasing the noise is what made me remove the cat & buy my street slayer w/ silencer removed...
 

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Hello, looking for opinions and insights. has anyone here looked at

after reading reviews this looks like a quality product. I am interested in improving performance not concerned about increased sound decibels. I like the idea of maintaining the Oxygen sensor. I will be using the aRacer SpeedTek RC Mini 5 Race ECU – Yamaha R3 - Norton Motorsports. to manage the engine performance. Thanks for reviewing.
 

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I've got a similar cheap exhaust installed with the aRacer Mini 5 ECU. The ECU won't use the O2 sensor as normally the quickshifter occupies the O2 sensor's port. left the 02 sensor plugged into the exhaust as I couldn't be bothered removing it!
 

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Did leaving the sensor plugged in effect the performance of the aRacer Mini 5 ECU, or is it not taking any data from it?
 

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Jesse from Norton MS believed it doesn't matter leaving it in, so I guess it's not active? When I have time I'll remove and plug it.
 

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That's what he told me too. Thanks for the input.
 
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