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Baffle for Open Megaphone with Reverse Cone

Started by SB107, December 07, 2020, 10:56:09 AM

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SB107

So, after 1 quick trip with the new build I decided it needs to be toned down. I've seen the pictures of the guppy baffle, so using that idea and simplifying it I came up with this. I will be wrapping it with muffler packing. My muffler is slightly different than No Cent's muffler, because it its an open megaphone with reverse cone, so I think its required that I use some sort of muffler packing.

Right now the wrapped portion is a Ø2.900" OD perforated tube (designed to fit in a 3" dia 18ga tube). It is roughly 8" long. Thinking the 8" might be a little too long, maybe I'll shorten it to 6".

Should I go down to a 2.5" dia perforated tube? 2" dia? Not looking to really pick up too much low end just want to tame it down a notch (or 5) for my sanity any any poor soul that rides behind me.

The endcap that the perforated tube mounts to will be machined. Would like to keep it simple so I can knock it out on an engine lathe and a mill. I could drill holes in it (the endcap) to allow more flow as well.

Any suggestions or ideas would be appreciated. Thanks.

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Mutant Motors 124"
161/148 STD, 158/145 SAE

kd

IMO that baffle will be wagging like a dog's tail in there.  I built an endcap for my 3" burns similar to No Cent's and added a modified SuperTrapp disc silencer on the end. I am confident it will easily flow more than the 3" baffle in the Burns megaphone. I did this to reduce the sound level but not at the expense of power.

Full disclosure though, I completed it the month COVID hit and have not been able to get across the border to get it re-tuned properly. I can not compare it to the original tune. The silencer has been manually tuned to be soot free and the tune installed is working well.  If you like, you can PM me with your email address and I will share a few pics with you.   
KD

HighLiner

Interesting ideas.  I have a Burns muffler similar to your description having nothing inside and I was told it can't have a baffle added.

kd

If you look into the rear you'll notice a perforated skin layer.  That's a baffle.  If it's the original offering I have found it'll likely be 3". They do offer other options now.  The 3" is actually a straight through baffle.   :hyst: :hyst:  I know, it doesn't really baffle too much. That's why I set out to build a tunable stinger / silencer for it.
KD

SB107

Quote from: HighLiner on December 07, 2020, 03:51:49 PM
Interesting ideas.  I have a Burns muffler similar to your description having nothing inside and I was told it can't have a baffle added.
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Like this?

I wanted to try to do a 3" baffle like I had modeled, the guppy one obviously makes power but as kd stated it would probably move around a lot. Maybe I could wedge it in before tightening so it seats inside the muffler?

I do really like the idea of the disks though. I think it would be no issue going straight to an open endcap. My cam doesn't want to peak until 4500 anyways.
Mutant Motors 124"
161/148 STD, 158/145 SAE

kd

Yep, no baffle in there.  That must be one ear drum splitting loud mother of an exhaust.  Using an end cap will definitely change the characteristics of that muffler and tame down the volume.   Expect it to pick up considerably on the left side for an increase in torque.  You will need to get it on a dyno to do it properly.  My goal with discs was to tune mine to best torque without negatively influencing top rpm right side power. 
KD

SB107

Quote from: kd on December 08, 2020, 07:21:29 AM
Yep, no baffle in there.  That must be one ear drum splitting loud mother of an exhaust.  Using an end cap will definitely change the characteristics of that muffler and tame down the volume.   Expect it to pick up considerably on the left side for an increase in torque.  You will need to get it on a dyno to do it properly.  My goal with discs was to tune mine to best torque without negatively influencing top rpm right side power.

Absolutely, it is brutal loud even with a full face.

I think we will actually tune the exhaust on the dyno, adding disks and see how we can manipulate the tq curve. I think that would be a very fun project/
Mutant Motors 124"
161/148 STD, 158/145 SAE

kd

 :up:   :agree:  The closest tuner I trust is 9 hrs away and in the US (MN).  I haven't been able to cross the border since March so I am at a temporary standstill.
KD

HighLiner

Exactly the same one I have.  I'll be watching for results!

C-Cat

My Burns megaphone has the 3in. scrabble Baffle. You can look down the megaphone and see the primary tubes pretty much the same as the one pictured above. IMO the baffle doesn't do much for sound deadening. Winter now, although i put a few hundred miles on it and like already mentioned "too damn loud".
Going to try a Supertrapp 5in. muffler on it (not cheap in stainless) without the discs and end cap at first.
Merc63 posted his 124 B2 build on here a few years back, he had good results replacing the Burns with the Supertrapp without any discs. I think if you go discs, it will take quite a few to not limit upper rpm power.
124ci. 07 Streetbob 161/145
110ci. '11 Roadglide  129/127

FXDBI

Quote from: C-Cat on December 12, 2020, 10:44:30 PM
My Burns megaphone has the 3in. scrabble Baffle. You can look down the megaphone and see the primary tubes pretty much the same as the one pictured above. IMO the baffle doesn't do much for sound deadening. Winter now, although i put a few hundred miles on it and like already mentioned "too damn loud".
Going to try a Supertrapp 5in. muffler on it (not cheap in stainless) without the discs and end cap at first.
Merc63 posted his 124 B2 build on here a few years back, he had good results replacing the Burns with the Supertrapp without any discs. I think if you go discs, it will take quite a few to not limit upper rpm power.

I played with a 5in supertrapp muffler ran all the discs and endcap and played with hole in the middle of the end cap and played with the hole size , Buddy is using it on a 117 now.  Bob

C-Cat

Merc63 said he tried the discs, but thought it was limiting upper end power and was easier to tune. Baddyna is also running a Supertrapp with no discs on a 124 and he said better low end TQ with the discs, but lost some upstairs. They both said it's a tolerable noise level even without the discs.
124ci. 07 Streetbob 161/145
110ci. '11 Roadglide  129/127

FXDBI

Quote from: C-Cat on December 12, 2020, 11:42:58 PM
Merc63 said he tried the discs, but thought it was limiting upper end power and was easier to tune. Baddyna is also running a Supertrapp with no discs on a 124 and he said better low end TQ with the discs, but lost some upstairs. They both said it's a tolerable noise level even without the discs.

Like I said I ran all the discs and put a hole in the end cap. Started @ 1.5 in  and used a cone stone to open it up . Did this is small increments until it had no top end loss and still had bottom end torque.  I really liked how it sounded, has a real awesome sound behind buddies 117.  I played with the discs and end cap on and off, found this to work the best of both worlds.  Have a fuel moto E-pipe now and couldnt be happier.   Bob

SB107

With a lot of good ideas from kd, I have a part I will program on a CNC that will allow me to tinker and do a few iterations to see which one proves superior. I think I can pick up 20ftlbs at 3k, still pull 150+ hp, as well as cut the drone out. I don't need the tq but I think it will be a byproduct of the sound cancellation coupled with pressure wave tuning capability.
Mutant Motors 124"
161/148 STD, 158/145 SAE

kd

No Cents and Strokerjk have already proven that was possible on a dyno with Ray's 124 by working the center hole size out slowly without using discs and stopped like FXDBI when the top started to show a shift. I believe 20# is possible and maybe more depending on how the actual pipe is performing with the cams and there is adequate intake to carry it. I forget what Ray and Jim got back. Maybe even more up top is available for the same reasons.  You should also be able to shave off torque in exchange for power at the top.  All this with noise (drone) abatement.  I believe this kind of win / win has enough value to justify the cost of a fixture (which will not be low) when weighed against benefit as mentioned.
KD

SB107

Here is an updated part that I designed to avoid using a CNC, as my free CNC shop is going gangbusters right now so we wont have a chance to get it set up. I think we will make 2 versions, one with the annular holes and one without and dyno them back to back. I can also open up the ID of the cone on the back side of the baffle for some potential tunability. I can also use this design and bolt in an off-the- shelf baffle to test it out (fuel moto tunable inserts come to mind). I shortened it up so there wouldn't be as much "wagging" going on. Baffle is 2.5". Thoughts?
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Mutant Motors 124"
161/148 STD, 158/145 SAE

kd

I think 2.5" will be about right depending on engine size and output.  A big block looking to produce all the way up will need the annular holes.  The Dragula 2.5" works well with my 120 but the Burns 3" tops it by 5 / 5 staring at 4,000 rpm. The Burns comes off the bottom lower though.  Both are loud getting on it and on the highway you should be wearing ear plugs.  Forget the stereo.
KD

SB107

Quote from: kd on March 02, 2021, 06:25:31 AM
I think 2.5" will be about right depending on engine size and output.  A big block looking to produce all the way up will need the annular holes.  The Dragula 2.5" works well with my 120 but the Burns 3" tops it by 5 / 5 staring at 4,000 rpm. The Burns comes off the bottom lower though.  Both are loud getting on it and on the highway you should be wearing ear plugs.  Forget the stereo.

I'm hoping the angle on the cone in the back and the angle of the cap itself will help break up the sound waves enough to kill drone. I think this is a good way to go but I might try to close up the end where the cone is and see what happens. Should be a fun project, trying to keep it simple and light.
Mutant Motors 124"
161/148 STD, 158/145 SAE

kd

Worth trying.  I'm not talking about "drone" though. I mean all out too loud to hear over in my experience.  My ears are ringing after running any distance at highway speed without ear plugs.
KD

SB107

Quote from: kd on March 02, 2021, 06:59:35 AM
Worth trying.  I'm not talking about "drone" though. I mean all out too loud to hear over in my experience.  My ears are ringing after running any distance at highway speed without ear plugs.

You're talking about your 3" baffled meg right?
Mutant Motors 124"
161/148 STD, 158/145 SAE

kd

Both. The Dragula too. I have the Burns toned down (with about 24 discs / open end cap) and to about the same level as the Dragula right now (maybe better).  Next is more discs and a closed endcap. It (Dragula) may have been quieter when new but I bought it used from a member here that IIRC wanted something with more bark.  :dgust:  I am not an old fogie when it comes to pipes but they are over the top for any duration.
KD

SB107

Quote from: kd on March 02, 2021, 07:25:56 AM
Both. The Dragula too. I have the Burns toned down (with about 24 discs / open end cap) and to about the same level as the Dragula right now (maybe better).  Next is more discs and a closed endcap. It (Dragula) may have been quieter when new but I bought it used from a member here that IIRC wanted something with more bark.  :dgust:  I am not an old fogie when it comes to pipes but they are over the top for any duration.

This thing is so intense the sound resonates in your head. Even with a full face and ear plugs. Just want to get rid of the resonation (drone) and as a byproduct tq will improve. If it only makes 150hp I wont be upset.
Mutant Motors 124"
161/148 STD, 158/145 SAE

kd

I can't imagine living with an empty megaphone.  We'll compare notes later.  I'm waiting on extra ST discs and the closed endcap.  Hopefully I will be able to get across the border to my tuner soon.
KD

C-Cat

March 02, 2021, 09:56:08 AM #23 Last Edit: March 02, 2021, 10:06:26 AM by C-Cat
At idle the Burns muffler isn't bad, as soon as you put load on the engine it's too much noise to be going down the road and also for me.I got a 5 in. Supertrapp Muffler and 24 discs to try. The Supertrapp will put the noise further behind me and with a longer baffle,  fiberglass matting instead of the Scrabble in the Burns 3 in. Baffle I think it will have more sound deadening and back pressure than the Burns even without the Discs. Going to experiment with it until I can get it to a Dyno. The Supertrapp has a 4 5 muffler body and 19in. long compred to 12in. Length on the Burns  , 3in. Baffle only the discs and endcap are 5in.
https://photos.app.goo.gl/c1327FHWoTsWiAcU7
124ci. 07 Streetbob 161/145
110ci. '11 Roadglide  129/127

kd

March 02, 2021, 06:11:09 PM #24 Last Edit: March 02, 2021, 07:13:04 PM by kd
Your system is very short. My Burns is 22" long overall including the collector, 16" of it being the actual megaphone body. It ends 2" past the rear axle on my touring 2011 RGU.  I had the head pipes made 6" (8"?) longer to pick up some torque.  I am using 4" discs which start out with the SuperTrapp heat shield directing the flow back. I have 24 discs on it right now with the first 3 discs (under the heat shield) spaced with one #10 lock washer for each layer. With the discs it ends 3.5" past the rear axle. I only had 24 discs and wanted to be sure I wasn't causing a rich burn. A spaced disc equals 3 discs.  All this with the ST open course open end cap. The ST open end cap equals 10 to 12 discs. Technically, I am now at about 36 to 38 discs with washers. If it had a closed end cap and no washers I could need as many as 40 discs .  I am presently using the tune I have for the Dragula 1 2.55 baffle   The pipe is not sooted up or burning too clean. I have more discs on the way along with a closed end cap.  When (if COVID restrictions lift), I can get across the border to my tuner south of Minneapolis / St Paul (border closed for over a year now) we will tune it for the open and closed end cap.  I already have the raw open Burns "as it comes" and Dragula tune.  I expect more than 1 day on the drum. It will be expensive but I am confident I have it right. It is set up with 18 and 12mm bungs and we use sniffer tube to confirm also so I expect the tune will be exact.  The tuner is a known excellent tuner.  It's a TTS Master Tune device. My goal includes making it more tolerable and also picking up the left side torque to match the 130+ I now get at 2500 rpm.  Another HTT member (NoCents) here has proven the torque rise can be done with a different fixture. I am shooting for that but a little quieter.

I would be surprised if you could change the baffle material.  Isn't yours welded in?
KD