That is pretty much what every silencer on every aftermarket pipe is - a perforated tube through the body,wrapped with fiberglass or steel. Pretty much what those glass packs are for cars. Look straight through them. They're loud.

Good muffling takes some baffles to change wave patterns or direction of waves. Perforated tubes only absorb some of the noise. The hard part is making the baffled internals in such a small space without being overly restrictive.

 

You appear to have skipped over a couple of pages so we'll explain it again.

Straight Through
Virtually every aftermarket exhaust muffler design involves a single perforated tube wrapped with packing material, with the end cap being in line with the perforated tube.

Exhaust gases enter the silencer, travel along the perforated tube, then exit *directly* though the end cap. The only exhaust dampening occurs in the perforated tube itself, though sound waves are still able to pass through to the atmosphere.



This design is widespread since it is very cheap to make. Straight through mufflers are also measurably louder compared to OEM mufflers (especially like comes on DOT legal dual sports). Many aftermarket mufflers often have even shorter bodies than OEM. Many advertise these cheaply made (but expensive to us) mufflers with names like "Big Gun" in order to make the noise seem sexy and desirable.


2016 KTM/Husky Exhaust
We've graduated beyond simple straight through design above. We're discussing ways to incorporate a design similar to what KTM and Husqvarna use on the 2016 EXC/FE models.

These lightweight silencers have a longer body sectioned off on the inside. The first 12" is straight through with fiberglass packing. From there the exhaust empties into a resonance chamber which itself is lined with a thinner rock wool layer, then exits via offset end cap opening. The gases (and sound waves) do not have a straight shot out the back of the silencer like with every aftermarket muffler sold.



Looking in from the back:



The body itself is larger in diameter, too. Some models also have a small perforated disk at the end cap, further reducing dB's while keeping desirable back pressure.

Decibel levels are DOT legal (around 80 to 82) with this new KTM/Husky muffler design. Obviously power is not affected - KTM is easily the fastest bike in class. These 2016 style mufflers are light weight and look good.

BTW, nobody is interested in hacking a heavy John Deere tractor muffler to fit on our bikes. I like the idea of fully chambered mufflers but it would need to be AL and look good.

Hope this helps everyone get on the same page.

 

Been on the same page all along. In fact I've been on this page before it existed. My SR500 with a straight thru muffler was so loud my brother and friends would not ride behind it (high pipe).

I tried building an internal Supertrapp set up in the megaphone, but the 500 blew the 3" set up apart, too small to function without like 18 discs. It needed the 4" version, which my 650 runs. But that would take away from the sweet reverse cone megaphone look. A work still in progress. When I get a chance and can get with someone who can weld I will try to set up a true chambered muffler. Possibly weld a couple louvered tubes together in an offset inside the megaphone, breaking the sound wave pattern. You either baffle the wave pattern or you choke it down. Both will cause restriction to flow, but if the muffler chambers are big enough the baffling will work best.


How heavy did you find the John Deere muffler to be? The threads I've seen have it at around 4 lb including mid pipe. Don't dismiss a very legitimate possibility because of the name of the part used. I'd take this:



over a stock muffler set up if it came to replacement.

Not horribly ugly, could even cut off end tube or add a turn down as some do. An aluminum or stainless wrap and it looks like a sport bike can. But that was a budget plan, and mentioned as a good possible replacement, weighing less than the stock muffler and probably the KLX 300 muffler.

 

The tractor muffler mounted on that KLR just doesn't do it for me aesthetically. Even if it were wrapped in AL. If I were modifying anything it would be the KTM muffler pictured before. I'd want characteristics of the fiberglass wrapped straight through (lower deeper note) with the quieter nature of the chamber.

Eager to see what Subseageorge comes up with in Indonesia. If his guy is able to make a muffler to fit our KLX250's based on the KTM design... and it's decent quality... I am hooked. His guy will have a small market to work from.

 

Finally got a best offer on the KTM silencer pictured right above. The end cap pulled off in a crash, but the goal here is to just see how it might potentially fit up, if at all.

 

All I said was don't dismiss a solution that can work well. You don't like it, fine. Fact is it is essentially the same kind of system used on most off road silencers, except instead of just a perforated core they use a louvered core which is likely quieter, plus only ends up at around 4 lb... and around a $100 savings for the rider who does not mind the lowly origins.

I don't get too shook up about aluminum or carbon fiber cans since there have been a number of posts in various forums where holes break out due to vibration and pressure. A stainless or steel can makes me happy since they don't usually break.

I will say factory aluminum silencers are usually heavier and better quality than aftermarket. And it will be interesting to see what comes from Indonesia. The easy way is the perforated core. The hard way is a truly chambered muffler.

 

Haven't dismissed it, but am not very interested in it.

Let's see how george's indo-muffler does, and I'll also chime in about the KTM muffler when I get it.

 

Update, He has finished the header and intermediate pipe. Looks great. he asked if i wanted anything special inside the silencer. So i just sent him a pic like this to see if they can do it or not. and i asked him to use screws rather than pop rivets, so i can strip it and see whats its like.




So he will talk to his fabricator and get back to me tomorrow.

 

Can we give some feedback or would he be up for working up a second variation? Wish I had your direct email to discuss to reduce the noise so to speak.

My initial observation is that the muffler in the pic above is a pure straight through design with a spark arrestor. The body (rivets to rivets) seems very short, almost like the DG style muffler which itself is obnoxiously loud even with their "quiet insert".

The KTM muffler uses a lengthy body containing mostly straight perforated core (and fiberglass backing) along with a 6" chamber at the back. The chamber is also lined with rock wool. The straight core empties into this chamber, and then the end cap exits the chamber but at a different plane to allow additional sound wave cancellation.

I would pay good money to have him build one like this to this specification. I don't even care if nobody else wants a quiet KTM style exhaust.. just want one for me. Electric bikes are coming and people aren't going to put up with 90 dB bikes anymore.

 

I am really interested in what you guys come up with, the KTM style silencer is what I would want.

Ed.