rexbirk

I have a number of 28cc 2 stroke gasoline engines and have not seen a truly quiet muffler system for them. I have heard some canisters that were quieter than the stock mufflers but they can be hassle. Anyone have an ideas? Have seen some external mufflers that were kind of like an external tuned pipe. I'm not opposed to the external types.

Almost seems like the four strokes are the answer although an expensive one!

AA5BY

I have a 28cc that had the stock side discharge muffler and it was kinda loud. The plane tripped on the down pipe bending it back and cracking the weld. I ordered another muffler from the engine supplier but the mounting was more centered and the muffler wouldn't clear the cowl so intalled a Zenoah 23/26cc steel muffler that bolted right on. A couple of hundred rpms were lost but half the noise is also gone. The 28 was very strong in the bird so the power loss isn't missed. I think any muffler that uses two smaller discharge ports rather than one larger will be a little quieter. But... I think your wanting more quiet than simply double down tubes.

Jtec markets what they call snufflers to bolt onto down tubes.

http://www.jtecrc.com/snufflermufflers.htm

I'm in fact building up a Spacewalker right now with a G-26 and as it is a lazy Sunday flier, I want it as quiet as possible so have ordered a pitts wrap around with the snufflers.

rexbirk

I have a high volume Jtec muffler on my 60cc Edge. It is quieter. Does not have the snufflers on it though. That may be the next step.

Don't know if the universal snuffler will fit my muffler on the 28cc though. Their website doesn't give much info.

pe reivers

If you find canisters a hassle, why ask?
Decent canister is MTW TD40
for tuned pipe I suggest the MVVS 3255
both systems will be a hassle in your opinion, but provide plenty noise attenuation and plenty of power. Better get used to the fact that two stroke muffler systems need lots of space if they are to be any good.

rexbirk

The problem I have with a canister is finding a header to fit my MLD-28 Engines. That is the hassle I have been having. The bolt pattern is the same as a DLE-30 but the height of the port is such that I can't make it line up with the canister tunnel. The header I have is corrugated stainless and wont bend enough.

Doesn't seem to be a lot of choices in headers for 28cc size engines.

Not familiar with the MTW TD40. Is that a product you sell? Still leaves me with the header problem. I'm not skilled enough with metal to make or modify one.

soarrich

My Feedback: (98)

Not all your noise comes from the muffler. The carb gulping air makes lots of noise, as does the prop. As Pe said a good two stroke muffler is going to take up room or power, your choice.

spaceworm

The Snufflers are basically tubular lawnmower mufflers that can be bought almost anywhere that has mower parts for three or four dollars. A simple modification makes them such they can be added to most exhaust systems. But of course, Jtec has already done that for you if you don't want to.

rexbirk

Spaceworm,

I have never heard a snuffler. are they much quieter?

AA5BY

I've not heard them either... but guys at the field who have, said they do reduce noise but if noise is a concern, join them and go electric... to wit, I repeated an ongoing mantra that I like planes that sound like planes... I'd not eat an apply pie that didn't taste like an apple pie.

acdii

I am half tempted to see if I can get scale exhaust headers and outlets for the DLE20 to fit my Mustang.  If its gonna look and fly like a Stang, it needs to be loud like a Stang!

w8ye

My Feedback: (16)

You need a lot of prop buzz when you do those fast fly-bys?

acdii

Heck I want it to RUMBLE as it flies past!

MTK

Look in the Pattern Forum. I have several different set-ups developed there....30cc SAP, OS33GT. 38cc Mintor, 40cc ZDZ and DLE55.

For a header that gets the exhaust back to center and drops it 1 1/2" (inverted set-up) look at the Hatori at Graves RC. Hatori makes headers to fit the OS33GT/DLE30/MLD28. They also make headers to fit the DLE55/DA50/DA60

Just a quick summary, for the very best attenuation, install the engine on a soft mount and use a pipe on it. Muffling intake noise (the reeds) can be a bit tricky but if you have the room, basically have the carb ingest air through an intake compartment. I typically will cut a hole in the firewal just behind the carb and install gas compatible foam sponge on the other side of the hole. The stuff Home Depot sells for working drywall does a good job and is gas compatible.

Lastly, prop selection is another major key. In piped set-ups you would want decent diameter but higher pitch. The 28-30cc engines work well on something like an APC 18.1x10, 17x12, 16x12......for even more noise reduction get a good 3 blade prop on your engine with adequate pitch something like a 16x10 3 blade.

One of the best set-ups I've come up with is for the DLE55....it is soft mounted and piped. The set-up that produces electric like quietness also includes a Mejzlik 20x12 3 blade prop. I use ESComposites pipes because they are some of the quietest and lightest by wide margin over aluminum stuff. But it's "hi-tech carbon composite" so you'll pay double.

I get the fact that what I described is advanced stuff but I've made it easy enough such that any sport guy could use the technology. It is going to cost some bucks so be prepared. Good luck... PM me if you need help

captinjohn

Well its off too thePattern forum to check this good data out. Thanks....MTK

rexbirk

I'm going to the pattern forum too! Not sure I want electric quiet but maybe somewhere half way there would be good.

captinjohn

Yes it is worth going to the Pattern fourm...went there...lots of good photos too!!!! Capt,n

dogshome

I've posted these up on other forums - sorry if you've seen before! Aluminium boxes are very quiet and not much heavier than a 'proper' muffler. You will lose some RPM, but gain friends





The 26cc was in a Yak54 - which fitted nicely in the large round cowl.

40cc pulls the Megawot out of a prop hang on 20*8 and sufficient for 4M glider towing. The previous engine was DL50 on a Zim pipe which was as quiet but accelerated all the way to the moon on a 22*8 if you let it!. <£5 vs a £110 exhaust system though. DL in a Goldwing Yak now.


If you already have an abundance of power, the metal box is a good alternative to cut the noise.

rexbirk

Looks nice. Where do the box's come from? Also, are they just hollow inside or do you put something in them?

rexbirk

I forgot to ask. How is the outlet pipe attached?

gr8flyer55

The boxes can be found here:
www.allelectronics.com
Do a search for part# 1590-b or 1590-bb


John

dogshome

I use the zinc based aluminium brazing rods to stick the pipe in - which is the full height of the box internally. There are 10 or so holes drilled into it as a baffle. The brazing is done at the internal end and round where the pipe comes out to seal it.

Making them is really easy. Just cut a hole for the exhaust port, two 5mm clearance holes to fix it, sick the perforated pipe in and then screw the lid on. Others have just screwed the pipe in with no brazing at all. A spacer from a thick sheet of aluminium is usually needed depending on engine. Just drill and files.

Silicon gasket seals the lid on. 26 and 40cc work well. Not tried anything bigge.


The boxes are a few 10s of grams heavier than a purpose built muffler, but are very quiet. Also cheap!

MTK

Well, 2 bladed props will get you on the quiet side of in-between. A soft mounted but muffled engine will be much quiter than a hard mounted engine so that's another option.

rexbirk

MTK,

Did you mean 3 blade?

MTK

No...

3 blade plus soft mount plus pipe = electric like quiet. THe poster didn't want it that quiet

2 blade plus soft mount and pipe will get you in-between.

Soft mount alone and everything else typical sport stuff (muffler, 2 blade, low pitched prop, etc) gets about the same as a canister.

Point is that there are a lot of things that one can do to quiet the crate with work on airframe resonance, exhaust note and prop. Then there are complimentary things like quieting the perceived reed noise.

And BTW, the power output is not harmed with the techniques I show; on contrary, pipes increase power (rpm and torque) so one can turn higher pitched props that attenuate noise better. Remember that the energy that has gone into making noise has to come from the fuel burned

pe reivers

Here is what will quiet down a plane.
if the muffler is ok, then prop noise, carb noise, and plane resonant noises rule,
1)  = prop noise (smaller diameter more pitch, more blades
2) = carb snoring noise (like a deer burling) Use attenuator like on fridge machines
3)= plane resonance. use soft mount, plane active dampers, passive dampers, non-drumming constructions