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Do you have to get a tuner if you remove the CAT? 2018 RGS. Wife says it is too hot on her right foot. Can’t really afford a tuner right now? Suggestions? Thanks.
 

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Can’t speak about the 18s, but my kitty ran away when I brought my ‘13 home. Zero ill effects at all. Lost the extra heat, gained a better sound, and gained a tiny bit of mpg. All wins in my book.









And yes, my kitty ran away while attached to the bike. I don’t know how that could happen..... Strange right?
 

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I gutted my cat not long after getting the bike .. Huge difference and a retune helps , but isn't necessary , if you cant afford a tuner get the XIEDs for catless , richens the fuel up a bit , used them in the 08 and this 11 before I put the FP3 in ...
 

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Yous Twos are definitely the exception to the rule as all I have ever heard is how shitty bikes run (my own included) if you mess with Air Flow and do not tune accordingly - Also, be VERRRRRRRY carful if you gut your own CAT to make sure you get every single teeny tiny ( @eddienelson dick size) piece of CAT out of there before you start the motor and suck that shit back in and then blow it out into your cans - That can really fuck a bike up good
 

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Pulling the cat does not require a retune.

There are no down stream O2 sensors and a new cat has little if any restriction in an oem exhaust system.

Before I went to all of that effort to cut it out, I would pull the shield and wrap it with header wrap.
 

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I can't believe you welded the cat can up while on the bike. I know it probably shouldn't be an issue, but with ABS and the ECU and whatnot, too much at risk for me. Good on ya though, looks like you had no issues.

I would agree that a tune is probably not absolutely necessary, but as mentioned XIEDs are cheap easy and probably all that's needed to help get it running happy.
 

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The trick to welding on anything that’s not on your welding table, is to keep the ground clamp on the part you are welding. It has to have a good connection. NEVER weld on it if you can’t keep the ground near the weld. The current will pass through things you don’t want it to. You’ll notice in the pics, the ground clamp was directly next to the weld. Electricity flows through the path of least resistance.
 

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I know about electricity, I'm an electronics guy. I also know the havoc drawing an arc, any arc in an electrical system, regardless of the ground position. It is reassuring, to me at least, that following best practice, as you have in this case, offers some safety there. Thanks for sharing.
 

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Removed CAT with Stock head on my 2011, 2013, 2016 with no tune and the bikes ran just fine. latter on the 2013 and 2016 I added Fuel motor 2-1-2 headed with No tuner bike ran just fine. No if all you do is pull the CAT it will not require a tune. Good way to do it is pick up a take off stock header and keep the CAT in one of them if you have any issue swap them out.
 

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Can’t speak about the 18s, but my kitty ran away when I brought my ‘13 home. Zero ill effects at all. Lost the extra heat, gained a better sound, and gained a tiny bit of mpg. All wins in my book.









And yes, my kitty ran away while attached to the bike. I don’t know how that could happen..... Strange right?
Now that's the way to do it. Remove the cat not the pipes! Cool.
 

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Pulling the cat does not require a retune.

There are no down stream O2 sensors and a new cat has little if any restriction in an oem exhaust system.

Before I went to all of that effort to cut it out, I would pull the shield and wrap it with header wrap.
I don't think I've ever seen anything you've said that I have ever disagreed with and I don't completely disagree with you here because the newer bikes the CAT doesn't offer very much restriction at all like you say. However, With the already lean MAP from factory removing the CAT could make it run just a bit leaner. It may even run fine to the rider but it may run hotter if only a little bit. I could be completely wrong as this is just my theory and I would be anal and tune it if it were my bike just to be sure. I could be this way because I have helped friends remove CATS on TC's and they did run shitty and we had to re-MAP them to get them to run like they should. I do trust what you say but I would still like to do some testing on a Dyno with the new M8's just to see what the difference is, if any.
 

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I don't think I've ever seen anything you've said that I have ever disagreed with and I don't completely disagree with you here because the newer bikes the CAT doesn't offer very much restriction at all like you say. However, With the already lean MAP from factory removing the CAT could make it run just a bit leaner. It may even run fine to the rider but it may run hotter if only a little bit. I could be completely wrong as this is just my theory and I would be anal and tune it if it were my bike just to be sure. I could be this way because I have helped friends remove CATS on TC's and they did run shitty and we had to re-MAP them to get them to run like they should. I do trust what you say but I would still like to do some testing on a Dyno with the new M8's just to see what the difference is, if any.
Removing the cat will not cause it to be leaner. The restriction in an oem exhaust is in the cans, not the cat.

The main issue with the new scooters is the need to maintain the oem tune to keep the warrantee. And I don't think the MoCo offers a flash for catless head pipes.
 

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Removing the cat will not cause it to be leaner. The restriction in an oem exhaust is in the cans, not the cat.

The main issue with the new scooters is the need to maintain the oem tune to keep the warrantee. And I don't think the MoCo offers a flash for catless head pipes.
i think you already answered the question, but would cat removal change back pressure and therefore the torque?
i'm satisfied (so far) with the way the M8 power kicks in but don't want to affect the low end (2250-4000 rpm) torque. it's addictive!

this bike is a lot of fun the way it is, but i don't want to jeopardize the engineers' intentions by major changes.
i have a feeling that they (HD) have a real winner with the M8, and the aftermarket needs a few years to catch up, so i'm kinda conservative with any "improvements."
 

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I have always wanted to learn to weld...........just so I can wear the mask and do that cool head nod thing that causes the mask to drop into place........jealous
 

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i think you already answered the question, but would cat removal change back pressure and therefore the torque?
i'm satisfied (so far) with the way the M8 power kicks in but don't want to affect the low end (2250-4000 rpm) torque. it's addictive!

this bike is a lot of fun the way it is, but i don't want to jeopardize the engineers' intentions by major changes.
i have a feeling that they (HD) have a real winner with the M8, and the aftermarket needs a few years to catch up, so i'm kinda conservative with any "improvements."

Exhaust restriction/flow is a function of the highest restriction in the system. In the case of a Harley w/oem cans, its the sound baffle in the can.

The back pressure is created by the sound control baffle in the can. Think 1/2 inch hole to keep it simple.

The cat is partially blocking a 3-3 1/2 x 2 inch hole. So we have a passage in the cans of less than 1 square inches. ,5 = .5 inches. And using the flow of two 1 3/4 pipes, a passage of 9 square inches on the cat. Less what the cat blocks. Automotive honeycomb cats generally flow 45%. So in round numbers, the cat flows the same as a pipe of 4 square inches. Or about 4 times the flow of the cans.

So as long as the oem cans are there, there is no flow benefit (or penalty) for pulling the cat.



Something that came up in another discussion was decel enrichment. Most production fuel management system add fuel during deceleration, to reduce NOx emissions. If Harley's have this in their software, then reducing speed by shifting down through the gears would make the cat hot. It would be burning the fuel that was added to reduce NOx. Which means that just using the brakes and then kicking down to first in the last 20 feet or roll would make for less heat in the cat. Someone still running oem fuel management could check this with an IR thermometer. Try rolling down from 60 both ways and see if engine braking results in more heat.
 

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Exhaust restriction/flow is a function of the highest restriction in the system. In the case of a Harley w/oem cans, its the sound baffle in the can.

The back pressure is created by the sound control baffle in the can. Think 1/2 inch hole to keep it simple.

So as long as the oem cans are there, there is no flow benefit (or penalty) for pulling the cat.

Something that came up in another discussion was decel enrichment. Most production fuel management system add fuel during deceleration, to reduce NOx emissions. If Harley's have this in their software, then reducing speed by shifting down through the gears would make the cat hot. It would be burning the fuel that was added to reduce NOx. Which means that just using the brakes and then kicking down to first in the last 20 feet or roll would make for less heat in the cat. Someone still running oem fuel management could check this with an IR thermometer. Try rolling down from 60 both ways and see if engine braking results in more heat.
heat doesn't really bother me that much. after riding the S+S 113 for 30K miles i've grown accustomed to it and dress accordingly. (sometimes, that scar on my leg gets boiled over once in awhile)

i'll see if i can borrow an ir thermo and check it out, tho. i know it sounds pretty cool when i engine brake. sounds almost like a diesel.

i'm at 4800 miles now and it seems that a slight decel pop is starting. pipe sounds great though.
is the ecm throwing more fuel to the engine now that the baffle is opening up?
 

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Do you have to get a tuner if you remove the CAT? 2018 RGS. Wife says it is too hot on her right foot. Can’t really afford a tuner right now? Suggestions? Thanks.
If you decide to remove the cat, you could always add a FP3 tuner or something similar to tweak the setup. Not sure about other setups, but with the FP3 tuner, after you are good with the setup, you can remove it. Not sure how HD would know, unless a dealer would have to check for the cat being removed. I am sure others might have more knowledge about that than I.
 
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