Muffler Mod Where and How Much?

[ChillyB]

Mostly I read to open up internal restrictions and make the exit hole bigger and/or more numerous. I have this nagging suspicion that while performance may improve by a seemingly haphazard approach, the mods may be far from optimized.

Will a big hole dead-center in front of the exhaust port perform the same as the same size hole coming out the side?

Will a hole hogged in top right corner perform the same as a pipe welded in same location that extends half the depth back into the muffler shell?

How does optimal exit size relate to displacement?

I dont see much information on correct way to mod a muffler to more or less optimize a muffler mod, mostly just remove screen, get out the drill. Are some methods better than others?

 

[Sierra_rider]

I'm not an expert on the subject, but do dabble in porting and exhaust modifications. My understanding is that saw mufflers don't really have a scavenging function like the expansion chamber on a dirt bike or kart engine.
The exhaust is so short, I just assume it's best to empty the exhaust as quickly as possible. I put a hole as close to inline with the exhaust port. I've heard numbers for the exhaust outlet sizes ranging from 70-90% of the exhaust port.

I've just resorted to picking a number based on how much noise I can live with. Some of my saws are at 100%, some are at 70%. My little climbing saws aren't that loud to begin with, so I go with a big outlet area. On the other hand, I'm more conservative on my 880...I even moved the hole off to the side of the front of the muffler cover, in order to "hide" it further behind the deflector I made. It's still loud, but nothing that ear muffs or good plugs can't kill.

 

[Woodslasher]

My muffler mods typically involve opening up the hole under the deflectors on 3-series Huskies, on Stihls it's more a case by case basis but I'll typically try to avoid making outlets bigger than the factory deflectors. Baffles and cats get removed, period. I've seen a handful of pretty new machines with scored up pistons or even melted cases from cat mufflers, so I get rid of those on every machine that crosses my bench.

 

[singinwoodwackr]

Depends on the saw and the muffler. Some are pretty darn good, stock. Some, like the Echo cs271s I just did were so clogged up with catalyst and other baffles I honestly don’t how the damn thing even ran, stock.
what saw are you looking at?

 

[Aknutter]

Husqvarna 350 , 44mm cyl I believe

 

[SawBawss]

Scavenging still applies with saws, If you open it up too much you will rob power and create more noise than performance. I personally prefer to stay off center from exhaust port and start opening up muffler outlet a little at a time or even add a second outlet. Just open it up until you are satisfied with the results. There are so many different ways of doing it and so many different saws that it is hard to make a one size fits all kind of mod.

 

[singinwoodwackr]

Husqvarna 350 , 44mm cyl I believe

Looks like the same muff as the 346xp...will get pics of mine...
45cc early 346xp...Dozer Dan build.

50cc, later model. CSJ build

 

[Sierra_rider]

Some of the exhausts I've done:

 

[ballisticdoughnut]

I generally stay within 70 to 80% of the size of the exhaust port on the outlet. I always run the spark screens. In my experience the best performing muffler will be essentially a hollow can with one appropriately sized outlet. Not all mufflers are going to fall into this category (internal baffles and so forth) so you just have to work with what you’ve got.

 

[chipper1]

Are you proficient at sharpening a chain, great gains to be found there. If you can't sharpen a chain well, any gains seen thru modding a muffler will be lost.
Also you will need to test the mods you make before and after to see if you gained anything or just made it louder, louder isn't always faster, and higher rpm doesn't always correspond to a saw that's easy to keep in the sweet spot.

 

[Farmer_Nate]

Old post, I know.

I concur, at least on the one and only muffler mod I've done, that one single opening on the side of the muffler worked nicely for me. I made it a little smaller than the exhaust port with a cupped sort of deflector to blow exhaust out basically over the chain. I completely removed whatever was inside the muffler and left an open cavity. There were structural tubes inside the muffler which I left in place, however. Saw responds quicker to the throttle now, or at least sounds that way. Idle sounds a lot tougher now. No idea if it improved performance, but it sure sounds better to me...music to my ears.

 

[Husqy41]

here u can see my husqy 41 mod, i close the stock outlet and put a 16mm pipe in with stock spark arrestor etc. , works just perfect for 40cc i think

 

[Farmer_Nate]

48cc saw...muff mod works very well. Nice pop pop pop sound, distinct puffs out front. I can clean my workbench with it from several feet away, like a blower.

Completely gutted all baffles, and opened the exit hole a bit, not quite as large as exhaust port from cylinder. Removed screen. Made the saw much more responsive, revs quicker when throttle is blipped.

 

[Husqy41]

top end build

 

[Xmaniac]

These tuned pipes rock for cutting up wood... not recommended for tree work... the bark box and other dual ported type mufflers will give you a little gain in power...

 

[thompsoncustom]

These tuned pipes rock for cutting up wood... not recommended for tree work... the bark box and other dual ported type mufflers will give you a little gain in power...

Any problems with over heating the saw with long run times? I see those on race saws and haven't heard about people running them on firewood saws tho I have considered putting one on my 660.

 

[Xmaniac]

Any problems with over heating the saw with long run times? I see those on race saws and haven't heard about people running them on firewood saws tho I have considered putting one on my 660.

You've got to do a little carb tuning, but I personally believe the saw runs cooler when decked, ported... I've got 6 saws that were modded and they all still haul ass after 8 year's of commercial production tree work....I got this pipe on ebay, CPI is the manufacturer... best $300÷ I ever spent... the gain is substantial....

 

[thompsoncustom]

Here's a vid where they piped a stock 660 and dyno tested it went from 7.05hp to 10.85hp that's one heck of a gain.



Only thing that worries me would be excess heat from jamming more fuel and exhaust gas back in the cylinder but maybe it's not a problem. If I knew I could cut all day with it i'd have one on my 660

 

[cuttinstihl]

Here was a ridiculously easy muffler mod that I did to my Makita 4300. All I did was remove the entire middle plate with the cat and baffle, leaving an empty can. She was awful loud when I first fired it up and I’ll probably have to trim some plastic to the top cover to avoid it from melting, but the sound is so nice that it’s worth that little bit of work IMO

Here’s some pics of the exhaust outlet

 

[Xmaniac]

Simple muffler mods will give you a little more power, make the saw breath better and sound louder... port and polishing the cylinder head will give you more. An unlimited coil helps too. Decking/squashing the cylinder and other machining techniques will go further if done right... then we get into race saws with nitrous, methanol and tuned pipes....