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Author Topic: Muffler mods  (Read 4114 times)

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Offline woodsdog2015

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Re: Muffler mods
« Reply #40 on: April 10, 2018, 12:30:11 PM »
Thanks fellas sounds like most feel that the saws will run better and cooler with a reasonable muffler mod.

               It absolutely does in my opinion.  Downside is more noise sometimes.  As was said, the extra heat is what  is detrimental to the saw, esp. when using in summer months.  Some will argue, but to each his own. ;)
Yes they absolutely last longer. :)
As I showed before my 27 year old 066Mag that I just rebuilt recently for the first time still has lots of life in the piston/cylinder.  Only had to replace a loose PTO bearing.
Thanks to its factory installed dual outlet muffler long before EPA and OSHA they built the saws to last.

(Image hidden from quote, click to view.)
 
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(Image hidden from quote, click to view.)

Holmen Tree, did you adjust the carb when you utilized the dual ported muffler so that the saw wouldn't run leaner and thereby have concerns about frying the piston and cylinder or was this all set from the factory?  It appears that most here enjoy the muffler mod but also do something on the other end, like switch to a less lean oil to gas ratio etc.  I guess I'm wondering if I purchase a muffler for my saw, they call them "test" mufflers, and do nothing to the carb or continue to use the factory 50:1 fuel to oil mixture ratio, will that be detrimental to my saw just by opening up the muffler.  The stock MS 362C muffler is just an open can with no baffle in it whatsoever so just adding a couple of more holes doesn't seem like it would lean the fuel mixture too much would it????    I'm throwing all of these scenarios out there sorry fellas.
I'd rather be in the woods.
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Offline HolmenTree

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Re: Muffler mods
« Reply #41 on: April 10, 2018, 01:07:09 PM »
Woodsdog, yes my 066 mag with dual outlet muffler came from the factory that way and from my information it also came with carb jetted richer.
To be honest I have no plans to do a muffler mod to my new MS261CM. I do residential tree removal and I think the extra noise would only be  detrimental to my business.
Out in the wilderness make all the noise you want.

Earliest Stihl factory dual outlet mufflers I can remember was an option for the 038 Magnum around 1985. But the 038 Super around 1983 may have got them first in the PNW.
Making a living with a saw since age 16.

Online mike_belben

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Re: Muffler mods
« Reply #42 on: April 10, 2018, 01:52:05 PM »
Fellas, a 2 stroke's lifespan is heavily correlated to being tuned correctly for the current operating condition.  There is no set it and forget it in a saw thats used in both summer and winter.  Every 10 or 15* temperature change really does need a little turn on the screws to run optimally.  Maybe a 70cc saw isnt too noticeable but on a tophandle you cant miss it. Theyre way down on power if out by 1/2 turn. 


 If tweaking screws isnt your bag then the Mtronic stuff may be the ticket for ya. 
Revelation 3:20

Offline HolmenTree

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Re: Muffler mods
« Reply #43 on: April 10, 2018, 02:06:44 PM »
Some of my saws lose that sweet spot at WOT with just a 10th of a turn on H.
Up here in the great white north, temperatures can vary big time. Go from 40 below and a few months later 110 above.
Cold temps needs the carb to be richer if set with summer adjustments. 
Making a living with a saw since age 16.

Offline woodsdog2015

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Re: Muffler mods
« Reply #44 on: April 10, 2018, 04:35:53 PM »
Woodsdog, yes my 066 mag with dual outlet muffler came from the factory that way and from my information it also came with carb jetted richer.
To be honest I have no plans to do a muffler mod to my new MS261CM. I do residential tree removal and I think the extra noise would only be  detrimental to my business.
Out in the wilderness make all the noise you want.

Earliest Stihl factory dual outlet mufflers I can remember was an option for the 038 Magnum around 1985. But the 038 Super around 1983 may have got them first in the PNW.
I believe I'm going to leave mine well enough alone too.  On another subject, and this is for anyone.  Does anyone know where I can get a full service manual for my Stihl Saws.  I did a quick google check and one popped up for the MS 362 and 362C (which is my saw) and it says 2010-9 so I'm assuming it was put out that year?  Is there anything a little newer?  My saw I believe was Manufactured in 2012 (I think) even though I bought it new in late 2015.  
I'd rather be in the woods.
MS362CM
MS251
CS-300
Homelite 8800
FiskarsX27

Offline Al_Smith

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Re: Muffler mods
« Reply #45 on: April 10, 2018, 07:06:36 PM »
I've never tried but I think you can get them through Stihl .Might just be the operators/ users  manual though come to think about it .If not you might be able to find one on flea bay .

Offline woodsdog2015

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Re: Muffler mods
« Reply #46 on: April 11, 2018, 04:12:17 PM »
Thanks Al yeah I do have the owners manual but I'm talking about the actual service manuals?  I find them very useful for saw maintenance and what not, I have one for my four wheeler and truck too and they have saved me a little $$$ along the way.  Plus, I'm just interested in them.  
I'd rather be in the woods.
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Offline Al_Smith

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Re: Muffler mods
« Reply #47 on: April 11, 2018, 05:30:22 PM »
I don't have the new service manuals because the newest Stihl I have is a pair of MS 200T's .I do however have the older  manuals on micro fitche and the parts lists in a big dealers book that must weigh 10 pounds .
Being somewhat of a collector of a number of things i have a library of service manuals covering everything from chainsaws to Bridgeport Milling machines .They are where you find them is all I can say .

Offline thedoublejranch

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Re: Muffler mods
« Reply #48 on: April 15, 2018, 12:36:48 AM »
You have to be careful, back-pressure actually aids a 2 stroke. So much un-burnt fuel escapes, and a backpressure pushes it back into the cylinder to be burnt. This is the principle in which an expansion chamber uses, the pulses reflecting back pushes un-burnt fuel back into the cylinder, creates a natural supercharging affect. Of course, our saws do not use this expansion chamber (I know hot saws do) and a little in moderation will help, but there is a point of diminishing returns ie power and also fuel consumption. So start with baby steps.

Normal soot and carbon can restrict it over time, boiling hot water clears the carbon/soot right off and a spark arrestor screen too
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Offline knuckledragger

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Re: Muffler mods
« Reply #49 on: April 15, 2018, 11:29:54 AM »
Wow, what an outstanding thread. I've been inside many, many saws. Very few echos, mostly stihl, husqy, and not quite as many Jonsered. Every one of you guys display acute knowledge of chainsaws and what impresses me is it's practical, applicable knowledge. I have grown accustomed to muffler modifications in conjunction with ten thousands squeeze on the jug. Running the 40:1 mix has proven to be the best mix ratio for me. I should also touch on this point, fresh air as well as vaporized gas runs faster and cooler over polished portals. Oh, please forgive me I started rambling on. My intentions were simply to compliment all of the knowledgeable people who submitted posts to this thread.

Offline knuckledragger

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Re: Muffler mods
« Reply #50 on: April 15, 2018, 11:42:33 AM »
Also, my 064 was manufactured in '92. With the muffler modifications and squeeze on the jug it provided over two decades of service before I restored the saw. I consider that to be proven longevity in the field... which is one of our goal as cutters of wood.

Offline HolmenTree

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Re: Muffler mods
« Reply #51 on: April 15, 2018, 12:45:53 PM »
Knuckledragger,  yep my 066mag manufactured in 1991 came from the factory with a dual outlet muffler,  and I do credit its longevity for maybe staying a little cooler.
But I think the main reason was to get the 066's h.p.up to compete with the Husqvarna 394XP.

There is debate on polishing ports. It is a fact that some high performance saws have roughed up surfaces and even screen material inside of intake manifolds to mix up the fuel mix charge a little better.  Even debate on polishing exhaust ports.
Making a living with a saw since age 16.

Offline knuckledragger

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Re: Muffler mods
« Reply #52 on: April 15, 2018, 01:21:20 PM »
Holmentree, I'm aware of different thinking on port polishing. I'm also a believer that what may work very well for one doesn't necessarily mean it will work for another. Stihl has a rough intake, I understand why. That only leaves the exhaust. Couple that with muffler modifications, and proper octane, mix ratio, fresh gas and there you go. A066 that provided 27yrs a 064 that provided 25yrs of service. Now then, all of my husqy saws, personal saws, have the intakes polished slick as glass. I will look at the intake about every twenty five hours of run time. The point of muffler modification is to me pointless if other steps aren't taken to facilitate and optimize said modification. Fraunk-n-Steen saws don't receive this type of attention because as a gift most are not appreciated like one that has been purchased with hard earned cash. I know that going in. This thread has become rather in-depth from a seemingly simple subject" muffler mods". In my opinion if one intends to modify the muffler on their saw they should have a direction, a plan so to speak, because like this thread it's really not as simple as it may appear.

Offline HolmenTree

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Re: Muffler mods
« Reply #53 on: April 15, 2018, 01:53:46 PM »
Good post knuckledragger, 
That's why I threw in the polishing comment. Like you said lots of variables, throw a tuned exhaust pipe on that saw and you have another whole different scenario with porting.
My 066 factory dual outlet muffler is loud and the saw  performs very well. But there is still a baffle inside the muffler over the cylinders exhaust port, combination is matched for the capacity of the carb.
I left that baffle in and kept the saw stock with no modifications, this very early S code 066 with it's strong port timing ,thin rings etc. was all I needed for what I was doing with  28" b/c. 
She's a keeper too. :)
Making a living with a saw since age 16.

Offline knuckledragger

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Re: Muffler mods
« Reply #54 on: April 15, 2018, 06:01:20 PM »
I'm not sure why I never purchased the 066. Hind sight being 20/20 I now believe I should have, but I have way too many saws as it is. I wasn't aware that stihl employed you. Not that I ever doubted your knowledge holmentree, it was easy enough for me to know you had vast amounts. The stihl thing makes everything come to light. Exceptional picture btw.

Offline HolmenTree

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Re: Muffler mods
« Reply #55 on: April 15, 2018, 06:29:59 PM »
I didn't stay with Stihl long though, big city and rush hours to the office wasn't my thing. But I did do field testing for them after when I got back into the woods.
Making a living with a saw since age 16.

Offline Al_Smith

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Re: Muffler mods
« Reply #56 on: April 15, 2018, 08:05:56 PM »
The back pressure or what might seem to be from a pressure can muffler doesn't really back charge like a tuned expansion chamber .Once the muffler pressure equals the outgoing transfer charge coming up on compression the flow stops .It's just about like shutting a valve .Some pressure build up is good because of both crankcase volume and carb size of a chainsaw as oppossed to say a dirt bike .
The reason old kart engines could run on huge megaphone exhausts was because they often had multiple carbs ,very large ones at that .If you megaphoned the average chainsaw engine you'd over run the carb at some point .Not to mention blowing your eardrums out .They most likely would not idle very well either if at all .

Online mike_belben

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Re: Muffler mods
« Reply #57 on: April 15, 2018, 11:02:23 PM »
A rough, dimpled or screened intake conduit will have more surface area for liquid fuel droplets clung to the walls, to mate with air molecules passing by.  These points will wick fuel onto them.    However in a two stroke it wont matter nearly as much as say, a fuel injected 4 stroke, because there is plenty of time for mixing.  The charge goes into the crankcase then through the transfers so the travel path is very long and turbulence is high.  On the 4 stroke, injectors are typically spray right at the back of the intake valve so there is very little time for atomization. 


I agree with AL on the can muffler back pressure.. A little pressure will help prevent all the intake charge from flying out the exh @ blowdown but a lot is going to limit the saws ability to pump air out, which will translate into high frictional horsepower.  FHP is subtracted from BHP so youd be down on power output from too much backpressure.

  As for tuned pipes pushing charge back in, i dunno.  Im having a hard time with that.   Ive long been under the impression that Inert, spent gas always contaminates a fuel charge and cools peak cylinder temp which means less cylinder pressure, thus less torque.  Manufacturers use the cooling effect of EGR to get temps down and dial in nox emmissions.  It always seems to cost power.

Conversely, a negative pressure wave vaccuums everything out of a cylinder, both spent and fresh gasses.  This scavenging effect always makes additional power by removing the inert gasses that limit cylinder pressure.  I know this is the case on 4 strokes making power by exh length tuning, negative pressure wave rarefraction travels back up to the port, caused from sound wave exiting the tailpipe.  P.H. Smith wrote a book full of pressure graphs from a machine that could look at exh pressure by crank angle.  I have it somewhere but its been almost 20 yrs, i dont recall if it covered 2 strokes.   

I have to wonder why dirtbike pipes arent glowing cherry red on every straightaway if theyre feeding that much fuel into the pipe.  Surely it would burn in there.. The pipe is beyond the fuel's auto ignition temp, no?
Revelation 3:20


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