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Discussion Starter · #1 · (Edited)
So from day one the muffled sound was not to my liking. My last two bikes were both s.o.h.c. 4’s, one had a four-inch open megaphone. I'm getting a little older now and at 25 and don’t feel the need to be obnoxious with my exhaust but the stock pipes on the fury just don’t cut it. I live in the wonderful state of California where there are talks from the C.A.R.B. (cailifornia air resources board) about smoging bikes. They will be specifically looking for aftermarket pipes and removed cat-converters. So for future smog and my lack of 600 bucks for new exhaust, my options are were limited. I found a happy medium. If you look down the tailpipe you will see two little holes. I decided to make those two holes into one big hole. I was surprised by the change in sound, it was exactly what I was looking for. It’s not too loud but now it can hear the bike with my full-face helmet on. I have not noticed a change in drivability so no need for EFI mapping and I think a dealer would be hard pressed to void a warranty over the modification. If you decide to try it, leave some feedback and tell me what you think.
 

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I did almost the same thing on my stock exhaust before buying my aftermarket pipes...but instead of the one big hole you made, I just bored out the two smaller ones into two larger ones. I noticed a big sound difference too, and the back pressure was still good enough for no air/fuel problems; therefore I didn't need a fuel management device either.

It's definitely a good mod if you are strapped for cash or just waiting on the next step of an aftermarket pipe.
 

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Umm... I know quite a bit of people in California with aftermarket pipes. I think you'll be just fine ;)
 

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As I actually like the bouble barrel oem exhaust on the Fury, I want to keep it. The only problem is, it's just a little to quiet for my likeing. I don't want to spend $1000 plus for new exhaust and a fuel controller, so Im going to give the holes in the OEM exhaust a bore-job. I'm going to enlarge the holes to half inch. I think this might just be what Im looking to hear.
Has anyone did this mod alone without tampering withe the catilist and had good results? Even though some have reported no popping on deceleration, I wonder if it still runs a little rich, but you just can't notice by ear. My thoughts are that in a worse case, I might only have to purchase a fuel controller after this modification, rather then exhaust and fuel controller together.
 

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I found a older thread on this mod:

http://www.furyforums.com/forum/fury-tech-performance-chat/404-exhaust-mod-fix.html

this thread links back to an older one where one guy said he did get a little popping but he also knocked out his cat. I DO NOT recommend screwing with the cat. As temping as it might be just don't do it.
Actually, *******, the popping is caused by the fresh air charge being "injected" by the pair valve (an afterburner effect, if you would). It wouldn't matter one iota whether the catalytic "sponge" were there or not. That being said, in this application the cat sponge also serves as a very effective sound attenuation medium, since its about 3-inches thick, top and bottom, and the entire mass flow has to pass through it. Therefore, you could entirely remove those little stinger thingys at the back end of the muffler and it would not get appreciably louder. I know; I did it.

By the way, unmodified, the popping sound is still there (unless you block the PAIR valve); you just can't hear it because it gets absorbed by the cat sponge.

Cheers
 

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Addendum;

As djdiscman so succinctly put it above, "Any popping on deceleration can be eliminated by blocking off the PAIR valves....". This is most easily achieved by blocking the PAIR valve solenoid pick-up tube, located just behind, and attached to, the air box mounting plate.

Cheers
 

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XxPatman;

You can bore out that end plate almost entirely; it will have little effect on the sound. I used a 3/4-inch bi-metal hole saw (from Home Depot). Simple, quick operation and NO, you will NOT need to install a fuel controller if this is going to be the extent of your modification.

Cheers
 

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Just a little confused here. One person says they noticed a big difference in sound and another says there will little effect on the sound. In hopes to just wake up the exhaust note a little bit, Im going to bore out the holes to 1/2" or 3/4" in size.
 

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I believe the statement of little to no change in sound is based upon the case of the 3/4" drilled holes versus the complete removal of the cat. I have 11/16" holes (I was trying to steer clear of the welds) drilled in mine and noticed a substantial sound change. Popping is not an issue as yet.
 

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Just a little confused here. One person says they noticed a big difference in sound and another says there will little effect on the sound. In hopes to just wake up the exhaust note a little bit, Im going to bore out the holes to 1/2" or 3/4" in size.
1/2" is almost ineffective. The I.D. of the tube behind those end-plates is 0.850". The I.D. of the recessed center of the end-plates is 0.750" (3/4"). The recess will keep the 3/4" hole saw centered while you're drilling. Piece of cake.

Try the 1/2" holes first (it only takes a few minutes), then you be the judge. I think you'll find that 1/2" doesn't make much of a difference. Now go to Home Depot and get a 3/4" bi-metal hole saw and bore away. Maybe this will be enough for you, maybe not. It's a perceptual thing, isn't it? I mean, how high is high, how deep is deep, and how loud is loud?

Now then, the incremental increase in sound level with the 3/4" hole wasn't significant, in my opinion. I started with 1/2" holes and was hard-pressed to tell the difference. Even with 3/4" modification, I still wasn't happy with the quality or volume of the sound; I subsequently gutted the whole muffler. Now we're talking quality sound!

Cheers
 

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So from day one the muffled sound was not to my liking. My last two bikes were both s.o.h.c. 4’s, one had a four-inch open megaphone. I'm getting a little older now and at 25 and don’t feel the need to be obnoxious with my exhaust but the stock pipes on the fury just don’t cut it. I live in the wonderful state of California where there are talks from the C.A.R.B. (cailifornia air resources board) about smoging bikes. They will be specifically looking for aftermarket pipes and removed cat-converters. So for future smog and my lack of 600 bucks for new exhaust, my options are were limited. I found a happy medium. If you look down the tailpipe you will see two little holes. I decided to make those two holes into one big hole. I was surprised by the change in sound, it was exactly what I was looking for. It’s not too loud but now it can hear the bike with my full-face helmet on. I have not noticed a change in drivability so no need for EFI mapping and I think a dealer would be hard pressed to void a warranty over the modification. If you decide to try it, leave some feedback and tell me what you think.
BTW, they rejected this bill in June and put it on the back burner till next year.. just an fyi... but most likely won't happen unless they go after cars as well for aftermarket exhausts... seriously doubt that will happen... again, just an fyi...
 

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I don't know much about this stuff, does widening the hole to 3/4" deepen the exhaust note as well as make it louder? Or does it just make it louder? I've never drilled one before and, unless I'm reading the above posts wrong, there seems to be some difference of opinion as to the change in sound......can anyone clarify for me?

Thanks,
Bob
 

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I don't know much about this stuff, does widening the hole to 3/4" deepen the exhaust note as well as make it louder? Or does it just make it louder? I've never drilled one before and, unless I'm reading the above posts wrong, there seems to be some difference of opinion as to the change in sound......can anyone clarify for me?

Thanks,
Bob
It will not deepen the sound (that would require a frequency change); it'll just make it a little bit louder, not much.

Cheers
 

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It will not deepen the sound (that would require a frequency change); it'll just make it a little bit louder, not much.

Cheers
You can change the frequency by changing the hole size... (This is an example, don't take it literal) It's just like a speaker box, you want a different frequency for your box to resonate at and also for the sound to come out differently, you change the hole (port) size in order for that to happen. You allow more air to come out of your port by changing the size of the hole to a bigger circumference, then the sound will most likely be lower by an octave or two.

If you don't change the hole size but a mm, you won't notice the difference, but a 1/4' and up, most likely you'll hear a difference in tone, but it won't be by much... but yes, it will change the natural resonance of which the pipes will sound by changing the hole size... And yes, it will also be louder, but if you make the hole too big, you will develop a natural declining curve in the way these things work.

Personally knowing how big that hole is in the OEM exhause, you could probably widen it all the way and notice effects both in volume and freq., but back pressure loss will affect the bikes performance. That is why many people write specifics in how much they open the pipe hole back there as to not lose the back pressure and thus, lose performance from their bike as well.

Cheers....
 
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