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Unpacking the cans... don't bother-

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Ha. Dave, I saw your cans for sale and wondered.... well one thing led to another and here I am, and so are you. too funny. Well, if they don't sell you can always make^^^ this^^^ work. I have a spare

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Nice Work!

Although you made it tougher on your welder, I think the flap he suggested would not make it easy to remove the steel wool.

But I am not interested in removing steel wool.

Two different ideas would be to increase the tube size of the core or to shorten the overall muffler.

Increasing the core size might be difficult unless you find second hand muffler cores, cheap. (from a wrecked muffler???)

I have a friend who made a muffler core for his Suzuki out of perforated aluminum heating duct material.

It worked great for about a year and then disintigrated, so aluminum is not up to the task

(except for maybe short term races, etc.)

The way you cut the muffler suggests that you easily could have shortened the muffler.

I like this idea, because it would bring the exhaust note towards the rider, and slightly reduce back pressure, and reduce rearward weight.

The trade off might be that it messes with the lines of the bike.

For the same reason some do not like the staintune muffler for our bike because it is shorter.

Thanks for the post. I was thinking of smoothing and widening the exit port, but it appears that gains would be minimal because the core is just as narrow as the exit port.

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You can get perforated steel sheet from McMaster-Carr. Quite a different assortment of hole sizes and patterns. Even different thinkness and material types.

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OK, I’ve got the unpacked cans on the bike. The db readings are 80-88db so not much louder than stock.


Out on the road, you only hear the difference when you open the throttle. Then you get a throaty roar.


So, overall, I’d say don’t bother with all this.


If you want to hear it, you can go to:




and download stock, open pipe, and unpacked videos.




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Well, just as an FYI... keep in mind that from the sectioned(cut in half) stock exhausts I saw in a thread a while back.... from what I recall, it's not a straight through pipe inside the can, but instead like an auto muffler, a multi path/pipe setup with at least 2 chambers.


So even with pulling out the packing, it's still not going to be quite as free flowing as aftermarket cans.



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The bore on the Mistrals is much larger than the stock pipes. What works for pipe organs undoubtedly applies here as well. Bass notes like larger openings, so unpacking the stock pipes will only go so far, probably reducing back pressure somewhat, but not making a significant change in the timbre of the sound.

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Guest rosso mandello

[Hello, I myst say that I´we done what could be done, and the result is not worth the trouble. I have opened the cans in both ends and ind the middle, just to find out that there is nothing you cán do there. Te hole silencer is build up in 3 chambers, the cambers are connected vi different tubes in varius lengts. So, apart from the unpacking, I could not get further.

Sorry for my English, did you all know that the total number of V 11`s in Denmark does not eceed 15 bikes.

greetings, Mogens Mortensen.

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  • 1 month later...
Guest BCRider

As an option to the limited MG selection for aftermarket cans has anyone ever surveyed the 600 supersport market for suitable substitutes? You'd need to buy a pair of whatever's but it may be an option.

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Guest Brian Robson

The most difficult part would be to have the connecting pipes match up and the vast majority of the replacement pipes (other than the MG Ti) have these pipes pre attached.

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  • 3 months later...

:bier: Now I've got this muffler thing sussed, at least I have a pretty good theory about how that back chamber functions, it's sort of a pressure relief valve, when exhaust pressure increases when you open the throttle, some of the gasses can force their way through all that steel wool and make it out through the perforations near the end of the tailpipe. That's why not much happens when you remove all that steel wool, the escape hole is pretty small. I left about a quarter of the wool in, little change in sound, then today I drilled a 19mm hole directly under the stock opening, big change, but not quite there, so I drilled a 13mm hole just to the outside of the top end cap nut, Bingo! Deep and throaty, not Too loud, I like it! :bike: I removed most of the material surrounding the stock exit pipe except on the bottom, then painted the inside and pipe flat black, you can't tell that it has been modified unless you look up there with a flashlight! :lol:

Have fun, Tom :rasta:

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  • 1 month later...

On the topic of "how to fix the overly restrictive stock cans for those of us with more time than money & even less sense," I picked up a pair of cans cheap for some Frankensteinian surgery...

[shoutout to Ben in Bev. Hills! You da man! Thanx again for the great price on your stockers!]


Here's the stockers, outer cover removed:



You'll note the E3 symbol & other EPA warning stuff imprinted into the material of the can. Obviously you'll want to make cuts on the opposite side from these... Also please note the very flat plug welds in detail. More on these later.


Since I'm a lazy bodger who doesn't want to take the time to saw/grind/nibble his way thru the shell, I followed the basic rule: when in doubt, cheat! [iE: I used a plasma cutter...] :D




Notice the bolt fittings and flat plug welds in the outer surface. The plug welds connect the internal dividers to the outer shell [one was defective; hence the red paint & arrow on the upper can to point out the leak. The fibreglas and outer cover contained it, but that can would have run noticeably "hotter" for the passenger]; the bolt fittings secure the outer cover and the passenger's heel guards on the outer cover. NOTE THAT THE FITTINGS FOR THE HEEL GUARDS ON THE UPPER SURFACE OF THE CAN ANCHOR INTERNALLY, WHILE THE FITTINGS ON THE SIDE THAT MERELY HOLD ON THE COVER DO NOT.(I was just lucky that I decided to skip the upper fittings entirely and so only had to cut circles around the two plug welds on the side.)


So here is the internal structure of the stock exhaust can revealed!

From left to right, we have 4 chambers: exhaust, resonance, primary resonance, resonance damper.




1st: Inlet from the collector enters & continues all the way to the 3rd chamber to the right. Two small pipes connect this chamber to #2, and a medium sized pipe much smaller than the inlet with a screened opening leading from chamber #1 all the way thru to the exhaust outlet past chamber #4 on the right. No, the end of the perforated pipe is neither open nor perf'd.; it's a blank end! Ergo outflow thru this pipe is reduced to perhaps 1/2 of its "normal" flow capacity...




2nd: Resonance chamber connected by a pair of approx. 1/2"dia pipes on both sides to chambers #1 & #3. Both large lower (inlet) & medium upper (exhaust) pipes have no direct openings to this chamber.


3rd: Primary resonance chamber. Large inlet pipe from x-over finally dumps exhaust gasses in here. Openings are by two small pipes connecting to chamber 2 and perforated divider to chamber 4. Medium upper pipe has no openings to this chamber nor should it, for obvious reasons. All of those advocating taking a drill bit on an 18" extension will wind up drilling a hole directly to this chamber, which will make your exhaust very noisy but not provide enough flow to significantly reduce backpressure!




4th: This chamber is the "damper" for the primary resonance chamber, having direct connection with chamber 3 to the left via the finely perforated divider between them. It is packed almost solid with stainless steel wool.




You can see in the pic below that the upper pipe has no connection to the contents of this chamber. (Please ignore the burned & melted sections of the steel wool; this is a byproduct of my using a plasma cutter running at probably 3x the needed current to cut these cans open...)




Since this 4th chamber has only limited exposure to chamber 3, and no outlet, it's pretty much just a damper for the spike pressures experienced in the primary resonance chamber to it's left. The two relatively tiny pipes communicating chamber #3 with the secondary resonance chamber (#2 chamber) will cause a lot of backpressure that will force some of the gas into the steel wool, but not much. Basically, the middle of the wad of steel wool is spotlessly clean, since no gasses penetrate that far to carry in carbon...


So what can be done with the stock pipe to reduce backpressure WITHOUT making it unsufferably noisy? Not much; due to it's very complex construction without any intent for dismantling [undoubtedly a requirement for various govt. approvals], it cannot be significantly redesigned internally or reconstructed.


In another post, someone suggested just removing the outer cap and drilling a bunch of holes in the interior endcap.



This will be the quickest & most widely accessible means of reducing the backpressure of the exhaust, since we now know that chamber 4 is: 1) densely filled with steel wool and: 2) doesn't connect with the outlet in any other fashion.


With all that steel wool in the way, it will still be fairly subdued, but also by bleeding some of the pressure off to the outside world will damp out the resonances & pressures internal to the can all the more effectively. In this instance, a whole lot of small holes will be more effective than a few large ones. No drill bit over 1/8" (eg., 3mm) need apply. All it takes is a Torx bit of the correct size to access it...


For something more comprehensive, we can look a little deeper:


To really improve the flow, cutting windows into the respective chambers [easily done by allowing .5" on leeway from any of the "attaching" welds: end caps, top lug fittings, plug welds holding dividers in place], then major surgery to the internal piping can be undertaken and the windows welded back up, ground flat and the original cover reinstalled. The result will be *much* louder, look stock, but should have increased flow. What to cut inside?


The middle ground: do the mod to the endcap, then cut a window into chamber 1 and cut off the perforated end to the outlet pipe. Button things back up.


The extensive cutting option. Where & what?


Window 1:

The primary inlet just behind the restriction. Cut it across at an angle, opening facing away from the outlet (perf'd.) pipe, then cut it square across again just before the divider, taking out a segment about 4" long. Wrap the outlet pipe in fibreglas cloth and wiretie in situ.



Window 2: Cut the medium (outlet) pipe behind divider #1 and before divider #2. Make these cuts at 45deg to the axis, like this... ---\ /--- and spaced to remove about 1" of pipe on the shorter side of the gap.


Window 3:

Nada, Nothing, Niente. There is no 3. Don't cut the window; this chamber will be unchanged.


Window 4: You will still need to cut window 4 even if you already did the "quick & dirty" endcap drilling previously noted. With all the internal changes being made, the outlet pipe needs access to the buffer area to mellow the exhaust noise. A small window will be sufficient; cut it so that you can pull back the steel wool and drill a couple holes across the outlet pipe in front of the bulge. Again, about 1/8" holes should do the trick.


Shove all the steel wool back in & weld the windows all back shut.


How much backpressure reduction will there be? My forecast:


Not enough to justify the work; only inveterate tinkerers should even contemplate it, for fun. Exhaust noise expected to increase dramatically. In all, it would make more sense to design a low-restriction muffler from scratch that will fit inside the stock covers. The same design using different pipe diameters to maximize flow would still be reasonably quiet but by using larger outlet & connector tubes, flow would be greater. Didja notice the flared ends to the connector tubes? Those are actually very important, dramatically increasing flow. You'd want to do that too with the bigger pipes. Both ends. Ideally, one tube of each pair should be 1/2 the length of its mate, which helps negate resonances. How much would it cost Guzzi to do this? Not much. How much louder would it be? Probably not enough to prevent them from meeting current noise standards. But I can't blame them for the design choices they made: the key was to standardize on one design for all markets, and the Swiss are notoriously tough in their noise standards. C'est la vie...


Well this was fun! I hope you all enjoyed it!



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