# Muffler Mod, how big is too big



## timberwolf (Feb 26, 2007)

I did a little testing on opening up a muffler on an 026, this was posted about the web, but did not generate too much interest, though maybe it could be helpful.

Basicaly what I did was weld up a blank muffler cover for an 026 with a front plate that could be easily modified with different opening sizes.

Each time I tried a new opening the saw was tuned by ear to the edge of 2 stroking and then I made several cuts in a 10 inch poplar taking the best time.

Saw is bone stock except for a improved 260 air filter.

What I found was from a stock opening to 120% of the exhaust port size there was about a 20% improvement in cut times. Going further up to 400% of the port area continues to give small gains totaling another 5%.

I did also find that maintaining a good idle became problematic over 190% of the port area.

Here are a few pics and graphsopcorn:


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## timberwolf (Feb 26, 2007)

*Graphs*

Here is the data visualized


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## oldsaw (Feb 26, 2007)

Nice work. Good job keeping records on your progress. That's what's missing when mods are done. Easy to infer that louder is better, but time is what tells the truth.

Mark


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## timberwolf (Feb 26, 2007)

There is more I want to do with this, but it all takes time.

How does a tube stack up to the round hole of the same diamiter?

Muffler temp, head temp and fuel consumption?

Also have two modified 026s, I would like to repeat the test with those saws to see if there are any differences? One saw is ported low for torque, the other ported very high realy designed to run on alky and pipe.


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## bwalker (Feb 26, 2007)

Good job, TW.
The only thing I would have done different would have been to use a tach vs. tuning by ear, which I find is notoriously inaccurate with some saws. I might also add a companion test in larger wood so as to ascertain the effect of ever increasing outlet sizes on torque.
The intent of my comments is not to pizz in your cheerios, but to stimulate discussion.


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## timberwolf (Feb 26, 2007)

I did use a tach to measure the setting as I could best determine by ear, infact I did a similar test a couple years ago and set by tach for the same RPM each time., the problem is that mixture then is set way too rich too keep the RPM down once the muffle is opened up and the saw wants to turn some RPM. This is also why I enlarged the filter area before I started, the old style 026 filter is very restrictive and is on the edge of being a problem with the stock meffler opening.

Once I set by ear I did a test cut then double checked it by richening a little and re cutting then leaning a little and re cutting, so I realy was hunting for the best cut time each time. With the first couple increases to the muffler opening the gains were pretty clear and it was easy to tune and see that the saw was tuned for the best cut time. However as the muffler opening became larger tuning became a little more dificult and the gains harder to see from one test to the next.

It is very hard for me to test and measure 1 or 2 % gains from one cut to the next, too easy for operator error or changes in the wood to skew the results. But I did my best to avoid this as much as possible.


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## bwalker (Feb 26, 2007)

Sounds like you where on top of it then.
Did you get the feeling that torque fell as outlet size increased beyond a certain point?


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## timberwolf (Feb 26, 2007)

No, torque stayed good.

Goin in I though there would be a point where it might start to miss in the cut, but didnt see that.

One surprise was, as I started to open the muffler up I needed to do more increase on the LS and actually needed to lean the HS a little. I guess the LS was over contributing. As the increased demand at HS was not nearly what the increased fuel demand was at LS, however the fuel trrough the LS can make up a good 1/4 to 1/3 of the total fuel flow at full RPM.

The major issue was having a decent idle above 190 % of the exhaust port the idle started getting a little touchy and I needed to bring the idle RPM up to keep the saw from either loading up at idle and stumbling on spool up or being too lean at low speed and reving on after the throttle had been dropped.


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## precaud (Feb 26, 2007)

Great info, thanks. I'm guessing this data can be scaled proportionally for other cc's with similar results, yes?


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## timberwolf (Feb 26, 2007)

In general maybe, but each saw has it's own muffler and port dimentions, port timing and RPM, so I would expect to see variation from one saw to the next.

Some saws are much more choked down to start with, so would show beter gains, some of the older saws were more open and less would be had by opening up the muffler.

I opened up a Cat muffler on a 359 and the gain was closer to 35-40% on the cut times.

Chain can play a role, if the chain is dull and your pushing for all your worth a muffler mod and some extra HP won't make any difference.


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## Jaxx (Feb 26, 2007)

Good info. The graphs were great. Thanks for sharing your work.

Jaxx


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## precaud (Feb 26, 2007)

Just curious, what's the diameter of the 026 piston?


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## chowdozer (Feb 26, 2007)

bwalker said:


> Good job, TW.
> The intent of my comments is not to pizz in your cheerios, but to stimulate discussion.



Wow!!! You're a changed man! What happened?


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## RiverRat2 (Feb 26, 2007)

*Dang it bwalker*



bwalker said:


> Good job, TW.
> The only thing I would have done different would have been to use a tach vs. tuning by ear, which I find is notoriously inaccurate with some saws. I might also add a companion test in larger wood so as to ascertain the effect of ever increasing outlet sizes on torque.
> The intent of my comments is not to pizz in your cheerios, but to stimulate discussion.




Don't you remember desiring torque in a saw dont have nothing to do with performance,,,, especially if you go up in log size???????
Just kidding,,,,,, I think you are right on target with your comment and question Tried to Rep TW but it busted my chops, guess you are it if it will, it wouldnt let me,,on either one of ya
Interesting Thread,,,,, More data is good!!!!!!!!!!!!


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## RiverRat2 (Feb 26, 2007)

bwalker said:


> Sounds like you where on top of it then.
> Did you get the feeling that torque fell as outlet size increased beyond a certain point?



I would have thought the samething about the T falling off???? :monkey: :computer:


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## bwalker (Feb 26, 2007)

> Wow!!! You're a changed man! What happened?


The differance is TW is not a hack.


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## Bowtie (Feb 26, 2007)

Timberwolf, If I may ask, what carb you using on your 026?


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## Lakeside53 (Feb 26, 2007)

Great work! It seems to validate that 125% of exhaust port area is a good rule of thumb for decent results.


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## timberwolf (Feb 26, 2007)

I have a few 026 carbs, with out pulling it appart I would guess it is a 426, not sure though.

I'm still a hack Ben, maybe just a refined one.


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## Lakeside53 (Feb 26, 2007)

precaud said:


> Just curious, what's the diameter of the 026 piston?



44mm


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## timberwolf (Feb 26, 2007)

Yes it does validate the 125% of port opening rule, not even bad for the 85% of flange rule. And in line with the 80 20 rule 80% of the gains made with the first 20 of the work.

On the flip side there is some to be gained to go beyond that point, I want to look a little more at the down side, the LS jet was getting opened up pretty good to keep it happy, I wonder how much that hurts fuel efficiency? Engine temperature also the extra fuel might be adding a little cooling to the mix?

Going to try to repeate it with a modded 026 later in the week.


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## Lakeside53 (Feb 26, 2007)

Do check your carb if you have the time. I've found the WT194 to be the best, and the stock 426 to (some saws) run out of adjustible flow...


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## Turbocaster (Feb 26, 2007)

Timberwolf, Thanks for providing the data on your 026 muffler modifications. I had just completed a modification of adding two 5/16 inch holes to both of my 026's. While the power increase was noticeable, I just didn't know if it paid to go further. You certainly answered that question.

I am totally impressed and appreciative that you took the time to do the test and that you let the rest of us know the results. :>)


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## sawinredneck (Feb 26, 2007)

AWESOME TW, just AWESOME!!!! I am blown away at you're thoroughness on this!! Great information, puts a lot of answers out there for the rest of us! 
I tried to rep, but you know..........................


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## RaisedByWolves (Feb 27, 2007)

How the hell did the page get so big?








TW (Dad?) I was following this elsewheres and I think that the addition of a exit tube will change the results some, but Im not sure which way.


The transition into the tube (Think radiused edges) may help also.


Im thinking that a tube will be more efficient........Er.......Somewhere.


Maby more flow? Torque? Same results with less noise?


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## timberwolf (Feb 27, 2007)

Thanks Lake, I will check the carb, it is possible it is a 194 too.


My thought on the tubes is also that they can offer more in the way of sound attenuation, I have some exhaust design software that has sound level prediction. From what it shows me the longer the tubes the greater the possible sound attenuation.

From Practicle experiience, if it is like the stinger on a pipe, making it longer holds more heat in the pipe and raises the pipes RPM, so I think it may be a greater restriction than just a plain hole. On the other hand, looking at fluid dynamics theory, flow through a hole in a plate has greater friction than flow out a nozzel shaped opening. From practical experience I found I could go to bigger opening with tubes and still keep the low end, but I want to test this in a more controlled manner.

But at this point it is easy to try the ported saws and see how they do.

Saw number one is a very strong woods saw built for torque with high compression in the 200 psi range, low exhaust numbers and a short blowdown. It is interesting, this saw picks up nearly nothing on pipe. My thought is that this saw will be hurt by the smaller exhaust port opening more than a stock saw, the reason being that there exhaust pressure BMEP at exhaust port opening is higher than stock and blowdown shorter, so if there is too much restriction to getting the exhaust out cylinder purity will take a dive and then filling from the transfers will be delayed. Because the exhaust port is wider and has a greater initial opening width combined with a higher BMEP the initial outrush of exhaust should be more intense than stock. I think the Modded saw should continue to gain decently past the point where the stock saw started experience diminishing returns on the increased opening. What you guys think?


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## oldsaw (Feb 27, 2007)

Okay, TW, enough blabbing, off to the next series of tests!!! We on AS have to know.

 

Mark


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## timberwolf (Feb 27, 2007)

I know, but I am trying to wrap up a $1,000,000 fire investigation and deal with lifes little quirks. Hope to do some more saw work later in the week.


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## Kneejerk Bombas (Feb 27, 2007)

I did a similar test, with a small echo, incrementally opening the exaust and doing timed cuts. Ended up getting my best time without a muffler at all. It sounded the best that way too.


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## timberwolf (Mar 2, 2007)

Had some time and gave the test a run through with the modified saw, I used the same bar and chain, though the chain was not realy enough for the saw and I was pushing too much to do the cut times and saw justice.

This saw is not a high reving saw, exhaust port duration is acctually a little lower than stock. Built for torque, that it has, will pull 3/8 8 pin on muffler. Though in this test I was using 8 pin .325 for both saws.

Here are the numbers, again experienced the same need to richen the LS on the first couple openings and acctually lean the HS. This time the gains did not level off as much as with the stock saw.

Again up arround 180-190% of the port area the idle started getting touchy and it was nessicary to crank up a few hundred RPM.


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## timberwolf (Mar 2, 2007)

Here are some graphs, I wonder if I had opening 0.63 and 0.73 mixed up?


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## timberwolf (Mar 3, 2007)

*Tuning by ear vs tuning to 14k each time*

I did another test today, this time as Ben Sugested before, I tuned to 14k each time.

It is clear that the gains drop off much quicker and virtually nothing is gained by a muffler opening greater than about 90% of the exhaust port area. As the muffler opening is increased, it did require richening the saw to keep the RPM within the factory 14k max, it was louder, would be burning more fuel, but did not appear to be producing more power.

So if someone wants to do a muffler mod and intends to keep the saw within factory RPM, the 125% rule likely is just making noise and spewing unburnt fuel for nothing. By this it looks like somewhere about 80-90% of the exhaust port area would be the sweet spot if RPM is to be kept factory.

One that has me thinking now is chain, seems some chains can take advantage of the larger opening and higher RPM beter than others, Need to look at this some more, but from what I saw today trying some chain a lighter chain can take advantage of the higher RPM more than a heavy new out of the box work chain.


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## Bowtie (Mar 3, 2007)

timberwolf said:


> I did another test today, this time as Ben Sugested before, I tuned to 14k each time.
> 
> It is clear that the gains drop off much quicker and virtually nothing is gained by a muffler opening greater than about 90% of the exhaust port area. As the muffler opening is increased, it did require richening the saw to keep the RPM within the factory 14k max, it was louder, would be burning more fuel, but did not appear to be producing more power.
> 
> So if someone wants to do a muffler mod and intends to keep the saw within factory RPM, the 125% rule likely is just making noise and spewing unburnt fuel for nothing. By this it looks like somewhere about 80-90% of the exhaust port area would be the sweet spot if RPM is to be kept factory.



This is good to know, as my mod is (close) to that range of 80/90% as per Lakesides advice. 1 question Timberwolf, what chain pitch and kind are you using on this 026?


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## timberwolf (Mar 3, 2007)

I have tried just about every 325 and 3/8 I could, the .325 Stihl RS is good with an 8 pin sprocket, but in all cases 3/8 oregon, carleton, windsor, or Stihl RS cut faster tan .325, both out of the box and square filed. Some of the .325 chain has smaller cutters and does not work worth a crap, the Stihl RS is the only one I found to work well in .325.

I run only 16 inch on the 026, have tried 18" and 20", but don't bother with that, just switch to a bigger saw to cut with a 20"


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## Trigger-Time (Mar 3, 2007)

timberwolf said:


> By this it looks like somewhere about *80-90% of the exhaust port area *would be the sweet spot if RPM is to be kept factory.



80-90% of the piston or the muffler side of the cylinder?


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## timberwolf (Mar 3, 2007)

Exhaust port area is always (as I see it anyway) at the piston, the flange is where it meets the muffler. 

I am measuring the port area in 2 dimentions height and width, in reality the actual port is three dimentional due to the curve of the cylinder wall, but close enough ehh?


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## Trigger-Time (Mar 3, 2007)

timberwolf said:


> Exhaust port area is always (as I see it anyway) at the piston, the flange is where it meets the muffler.
> 
> I am measuring the port area in 2 dimentions height and width, in reality the actual port is three dimentional due to the curve of the cylinder wall, but close enough ehh?



Thanks...........I've enjoyed this thread, appreciate you sharing
the info


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## stihltech (Mar 4, 2007)

*Hmmmmm*

Makes me wonder if the muffler has a small effect on the exhaust wave like a pipe does.
Is that little hole we begin with actually keep some of the raw fuel from escaping out the exhaust?
I am sure it is still an EPA thing, but it does make one wonder if muffler design could have an effect on the power curve.


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## 046 (Mar 4, 2007)

this is only verifying what old timers have said for the longest time. 
open up your muffler to 85% of exhaust port. start smaller for it's easier to go larger than reduce in size. 

I'm insulted ::hmm3grin2orange: no one has remembered my spaghetti method of determining opening size. 

simply fill exhaust port full of spaghetti, then count. reduce number by 15% to come up with size you need.


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## timberwolf (Mar 4, 2007)

Yes it confirms it, but for me it clairifies some things too.

If factory RPM max is to be respected 85%

Stock Saw up to 125% if RPM is increased above factory spec

Modified gains can be found over 150% if speed is your objective

I want to do some testing on heat and fuel consumption next, bought an IR temp gun yeasterday.

Like the spagetti method, KISS

As far as any ruels of thumb off the size of the exhaust port flange, I would dump that idea esp if the saw has been modified.


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## bwalker (Mar 4, 2007)

TW, I never set a saw to the arbitrary Max no load numbers provided by the factory. I use a method I learned in my dirt bike days, which I call the cut and feel method. In a nutshell you start out rich and lean the saw out till you achieve max cut speed. You them record the RPM and use that as a target to tune to in the future.
i have found most of my saws impossible to tune by ear, but I have hearing damage from shooting guns and exposure to open stingers exhausts.


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## manual (Mar 4, 2007)

046 said:


> this is only verifying what old timers have said for the longest time.
> open up your muffler to 85% of exhaust port. start smaller for it's easier to go larger than reduce in size.
> 
> I'm insulted ::hmm3grin2orange: no one has remembered my spaghetti method of determining opening size.
> ...



Don't worry some of us remember.


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## Erick (Mar 4, 2007)

*WOW*

Man and to think I've been skipping over this thread. Excellent job TW  its one thing to drill an arbitrary hole in the muffler and "say" it runs better, its another to document and prove it.  Thanks for putting in the time and effort on this one and for posting the results a lot of good info. I always appreciate when people take the time to do things right. Keep up the good work and let us know what you find.


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## ford832 (Mar 4, 2007)

stihltech said:


> Makes me wonder if the muffler has a small effect on the exhaust wave like a pipe does.
> Is that little hole we begin with actually keep some of the raw fuel from escaping out the exhaust?
> I am sure it is still an EPA thing, but it does make one wonder if muffler design could have an effect on the power curve.




It definately should as the backpressure wave is responsible for keeping the incoming charge from escaping before the piston closes the port-on a dirt bike anyway-not enough backpressure=lost power.I always thought chainsaw mufflers were a little crude compared to a bike.I think all saws need a proper expansion chamber,can and stinger I'll take mine in nickel plate thank you very much 
Great thread and great info TW!!!! I'll rep if I can figure it out.


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## timberwolf (Mar 4, 2007)

I realy enjoy this kind of experimentation, to work with ideas and realy get an understanding of how and why things work. Thanks for all the feedback and ideas.

With fuel consumption I am thinking of feeding the fuel from a small graduated bottle rather than the fuel tank, that way it will be easier to keep track of the fuel used.

My question is should I track fuel useage based on operational time or work done. If I mod the muffler and the saw cuts faster but burns more fuel the efficiency might be the same, so measuring fuel consumption over time is flawed, maybe it would be beter to measure how much fuel is needed to make a certain number of cuts in the same sized wood? Though to check fuel consumption at idle it would still need to be measured over time.


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## timberwolf (Mar 4, 2007)

As you mention Ben, a good idea to know at what RPM your saws cut best, I have found this to be helpful, but worth keeping in mind that setting the saw at 15,000 where it cut best one day could be way off another day with a different bar and chain, also changes in temp, weather or elevation could throw off the tuning to a known number approach. If getting down to racing I have even found I can run a hair leaner for 2 cuts in smaller wood than 3 in larger wood.


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## Industry (Mar 5, 2007)

Definitely had to rep you for this. Excellent job, and keep the reports coming. Information is great. I can't wait to start modding saws.


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## timberwolf (Mar 5, 2007)

Did a little work on fuel consumption this afternoon. The results surprised me, will post the results as soon as I clean up the numbers and plug them in.

What do you guys think opening up the muffler does to fuel milage?


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## hokiebob1 (Mar 5, 2007)

This is an excellent thread. I work with engines/dyno's every day and jockey the data for a living so this peaks my interest. To me, opening up the port should increase the efficiency of the engine to a point, actually improving "fuel economy" at a given RPM. At some point with larger opening, it may go the other way as efficiency will go down. If tuning by ear, ie. likely higher rpms, fuel economy may stay the same, as any efficiency gained will be traded for higher rpm's.

Thats my guess, but data don't lie.

As for the question on the proper way to measure the fuel economy, it seems to me that the best way would be to measure it against number of cuts, not time. Think of it like gas mileage in your car--you measure in miles, not number of hours until you get there.

thats my $.02, but I'm very interested in the data.

Great Job!


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## timberwolf (Mar 5, 2007)

For the fuel test, I rigged up a 2 oz (60ml) bottle with 3 lines, one for fill, one breather, and one to the carb. For each test I filled it to the top of the lines, so I should have been within 1 or 2 tenths of a ml each time. After each test I refilled the bottle with a graduated syringe. Using the modified saw and square chain.

For the test I put on a muffler opening and tuned the saw by ear, double checked the RPM on the tach, shut it down and refilled. Then cold started and made 5 cuts in 10.5 inch poplar, shutting the saw down as the last cookie fell. 

Here is the fuel consumption numbers ml for 5 cuts

17.0 Opening 0.09
16.4 Opening 0.18
15.8 Opening 0.27
15.0 Opening 0.36
14.8 Opening 0.45
14.6 Opening 0.54
14.9 Opening 0.63
16.2 Opening 0.73
17.2 Opening 0.79
17.4 Opening 1.50

Fuel Efficiency acctually improved as the muffler was opened up, but dropped off about the same opening as improvements started to decline on cut times, only with very large openings was fuel consumption worse than stock. Don't know if this would be the same with a stock saw?

By time the saw uses more fuel as the muffler is opened, so the tank gets dry sooner, but the woodpile gets bigger faster. Too a point.

But I think this is just part of the story, It seams there is a lot of LS ajustment made, and a saw spends a lot of time at idle, so need to check that too.


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## hokiebob1 (Mar 5, 2007)

Timber, your x axis is in square inches-on your particular saw, how does that relate the exhaust port size....ie. .45 in^2 = 85% exh. opening.

The fuel economy data is interesting, but it raises the question....would you rather have fuel efficiency or quicker cuts. I know what the EPA would say, but would all users want quicker/more powerful cutting?

Cutting faster sounds like the hot setup to me.


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## timberwolf (Mar 5, 2007)

Just go back in the graphs posted earlier and the info is there.


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## hokiebob1 (Mar 5, 2007)

Thanks, I found it in the excel sheet.


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## sperho (Mar 5, 2007)

Outstanding timberwolf - great work. I just bought a MS261 Pro and was going to probably open up the muffler after the warranty expires next year. I wouldn't mind gaining a little power, presumably run a little cooler, and yet have a long lasting engine in my saw. Assuming these are my reasoning for a mod, it seems like two 3/8" holes added to the muffler and WOT RPM set to 14k is the ticket? Sounds like a pretty cheap 15% gain in power to me.


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## Lakeside53 (Mar 5, 2007)

2x 3/8 is what I've always done.. Timber shows there may be a little more to be gained though, but in the absence of his great data, I played it safe. 

If the saw is well broken in, and you like to be close to the edge (I don't 'cos I don't watch them all that closely thoughout the cutting days..) take it up to 14,500..... Then you can give those -026 wannabees (5100) a run for their money... opcorn:


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## bwalker (Mar 6, 2007)

> s you mention Ben, a good idea to know at what RPM your saws cut best, I have found this to be helpful, but worth keeping in mind that setting the saw at 15,000 where it cut best one day could be way off another day with a different bar and chain, also changes in temp, weather or elevation could throw off the tuning to a known number approach. If getting down to racing I have even found I can run a hair leaner for 2 cuts in smaller wood than 3 in larger wood.


 Given cutting attachments stay the same I have had excellant repeatability using this method. IN fact I have never felt a saw was off using this method and as I am sure your aware I am really picky about how my stuff runs.


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## Erick (Mar 6, 2007)

I've opened the muffler on my MS260 pro to exactly (measured) 90% of the exhaust port and have felt the gains, although I never measured them I always knew they were there, now we have your data, which confirms it.



> By time the saw uses more fuel as the muffler is opened, so the tank gets dry sooner, but the woodpile gets bigger faster. Too a point.



This was my personal feelings as well, the saw defiantly runs out of fuel faster but I get the work done faster too with less effort on my part. I always figured the saw got about the same number of cuts for the amount of fuel used, the work just got done faster, and therefore efficiency would be about the same as stock. I was surprised (and pleased) to know that efficiency was actually better. 

Thanks again for putting in the time and effort.  this is an excellent thread with some excellent information. I'd like to see some more threads like this on AS, non-biased, no "opinion's", just the facts, and you can't argue with the facts. Keep it coming TW (and others)


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## timberwolf (Mar 15, 2007)

Did a little more work. this time measuring the idle fuel consumption, I tried to keep the RPM as close to 3000 as I could, but as the opening got up arround 100% of the port opening the saw becam difficult to keep running at the same speed for the 4 min test. by the time I was up to the full opening the idle needed to be cranked up to nearly 3750 just to keep it stable.

As you can see fuel consumption at idle sky rockets as the muffler is opened up. Jumping from only using about 3ml per min at the smaller openings to over 3 times that amount fully opened.

Second graph is the combined fuel consumption 100% duity cycle (in the cut all the time) 50% duity cycle and 25% duity cycle. These were corrected to reflect the amount of cutting done by the stock opening in 1 min.

This is a very high compression saw with short blowdown, so it should be expected to waste some fuel at low speed.

I did some temperature measurments too, but need to enter them in.


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## sperho (Mar 15, 2007)

Would it be possible to post your spreadsheet for those of us who have Excel?


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## timberwolf (Mar 15, 2007)

I will try, it might work, but I had problems in trying to post an XLS file last time I tried.

No go!

Does not look like AS accepts .xls files for upload.


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## XJWoody (Mar 15, 2007)

timberwolf said:


> I will try, it might work, but I had problems in trying to post an XLS file last time I tried.



Might have to make a copy of that file & save it as HTML or maybe a TXT. I am unclear what AS allows as far as file upload formats.


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## timberwolf (Mar 15, 2007)

Can cut and paste to word and save as a .doc, but none of the math or functionality of and .xls file would be transfered.

.doc seams to keep the rows and columbs, .txt did not, .html got wacky too.


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## Lakeside53 (Mar 15, 2007)

timberwolf said:


> I will try, it might work, but I had problems in trying to post an XLS file last time I tried.
> 
> No go!
> 
> Does not look like AS accepts .xls files for upload.



ZIP it first.


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## sperho (Mar 15, 2007)

Lakeside53 said:


> ZIP it first.



If that doesn't work for some reason, I'll host the file and link to it in this thread...


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## ispansco (Apr 2, 2007)

hello everybody.


Fantastic posts for me. congratulations for the a lot of useful information I have found in your web and due to it I have bought my first chainsaw(Husqvarna 346xp) .Thank you very much.

I am sorry because don't know English very well.:bang:


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## XJWoody (Apr 2, 2007)

Welcome aboard Ispansco.


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## scotclayshooter (Apr 13, 2009)

timberwolf said:


> There is more I want to do with this, but it all takes time.
> 
> How does a tube stack up to the round hole of the same diamiter?
> Muffler temp, head temp and fuel consumption?
> ...



Hey TW theres a thread going asking about tubes rather than holes, Did you ever do any testing on the shape of the outlet other than the zero backpressure muffler?

http://www.arboristsite.com/showthread.php?t=96073

Im thinking the pipes would need to be too long to be of any benifit.


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## stihlhere (May 27, 2009)

*Timberwolf*

thanks for all the reserch on the 026 i looked at your charts and decided to inlarge the stock hole to 31/64 altho most people just add two smaller holes above and below. The saw may be a little faster (no timed cut) ( cutting 10 dry pinoak limb in a vice) but mutch more tork than before mod, i could not push saw much(20'bar) now i can stand on it with no stall.


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## stihlhere (May 27, 2009)

*Timberwolf*

You may have enjoyed all that port testing on 026 but I loved all the fact that you took time to post it. Again I really appreciate it. 
Ok I have read about problems with h adjustment on 026 (my muffle had no baffles just a very small exhaust hole) after mod i had to adjust L screw more than H. I thought something was wrong so i screw L in until saw died the backed out until it would run and then screwed H in until it would not rev and backed out until it would then i set wot. this thing will scream leaned out when i try to go just a little further to richen it dosn't sound rite alltho rpm come down then if i keep holding wot no matter how rich i get it i cant drown it out and saw will eventually take gas and begin over reving. 
is this two stroking need help


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## Wild Knight (May 27, 2009)

timberwolf said:


> Had some time and gave the test a run through with the modified saw, I used the same bar and chain, though the chain was not realy enough for the saw and I was pushing too much to do the cut times and saw justice.
> 
> This saw is not a high reving saw, exhaust port duration is acctually a little lower than stock. Built for torque, that it has, will pull 3/8 8 pin on muffler. Though in this test I was using 8 pin .325 for both saws.
> 
> ...



On one data sheet (post 30), you show stock WOT RPM's being greater than mod WOT RPM's, yet cut times go down. Why is this? (Rows 16 and 17)


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## Wild Knight (May 27, 2009)

How do these rules change on larger saws (70-90cc)? How does the ratio of cylinder port area to muffler port area change as the cc's of the saw increases?


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## Sawdustmaker (May 27, 2009)

stihlhere said:


> You may have enjoyed all that port testing on 026 but I loved all the fact that you took time to post it. Again I really appreciate it.
> Ok I have read about problems with h adjustment on 026 (my muffle had no baffles just a very small exhaust hole) after mod i had to adjust L screw more than H. I thought something was wrong so i screw L in until saw died the backed out until it would run and then screwed H in until it would not rev and backed out until it would then i set wot. this thing will scream leaned out when i try to go just a little further to richen it dosn't sound rite alltho rpm come down then if i keep holding wot no matter how rich i get it i cant drown it out and saw will eventually take gas and begin over reving.
> is this two stroking need help



do a search on tuning a saw, this does not sound right.


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## blsnelling (May 27, 2009)

Sawdustmaker said:


> do a search on tuning a saw, this does not sound right.



+1. You also should start a new thread rather than clutter this one up. You'll get more visability that way too.


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## stihlhere (May 27, 2009)

i tuned my own saws forever and never had this problem.# but just to let you know i read all those before i posted.# I thought i had heard something about some models wont richen up enough.# wondering about carb mod or replacement.# I have a few ms290 carbs dont know if they would# be any better.# That being said i removed a 18" oak today ant the 026 just riped compared to before It also cranked easier.


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## woodyman (May 27, 2009)

So do I have to cut my tubes off or can I leave them on?I really want to leave them on but I want the most power and torque I can get.



These are on my Snellerized 359.


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## Crofter (May 28, 2009)

Nah, dont shorten them; cut some notches in the ends and they will double as dawgs!


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## blsnelling (May 28, 2009)

Crofter said:


> ..they will double as dawgs!



That would be *hot*dawgs, lol


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## timberwolf (May 28, 2009)

yeh, one dawg-gone-right and one dawg-gone-left...


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## nmurph (May 28, 2009)

TW,
i just modded my 026 by enlarging the round hole to a 1.5" X 1/2" oval hole. is there any need to go larger?


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## Wild Knight (May 28, 2009)

wolf: they've already been buried in this thread. see posts 70 and 71 please.


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## timberwolf (May 28, 2009)

1.5 x .5 is plenty esp for a stock work saw.

Never found much difference related to saw size, port openings seem to be fairly porportional to displacement. Bore to stroke ratio plays a little with it as well as RPM though which affects bleed down period as well. Muffler volume factors in also. A large volume muffler is softer in terms of building back pressure right after exhaust port opens and will work with a smaller outlet than would be ideal for a small volume muffler.


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## mtngun (Apr 16, 2010)

Bumping this classic thread. :rockn:

Gist of TW's tests was, muffler exit should be about 85% of exhaust port area, give or take. Beyond that, more noise and only a tiny increase in power.

But ..... TW did not use a spark screen. 

I'm guessing a spark screen restricts flow considerably ? 

Guess that's another test that could be done........ if someone has the time.


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## L.R. (Sep 28, 2010)

mtngun said:


> Bumping this classic thread. :rockn:
> 
> Gist of TW's tests was, muffler exit should be about 85% of exhaust port area, give or take. Beyond that, more noise and only a tiny increase in power.
> 
> ...



My tach is on order... Would be fun just to duplicate the test with a different saw.

Just comparing performance before and after a specific mod can be compared to this data set, carry a pen and paper, people!


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## timberwolf (Sep 28, 2010)

But ..... TW did not use a spark screen. 

I'm guessing a spark screen restricts flow considerably ? 

It will but depends on how the screen is positioned, if it is tight to the opening then the screen should cut the flow in about half. Something I have been thinking of doing some flow bench work on.

But if the screen is held off the actuall opening so that there is a larger area of screen availible (at leat twice the area) it likely makes little difference.


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## OrangeRidge (Jul 28, 2013)

*.... three years on .............*

Bought a MS260Pro last week and drilled a couple of 3/8 holes in the muffler this morning . Seriously better in the cut ! This is a superb thread by Timberwolf


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## Robin Wood (Aug 7, 2017)

ive been meddling with MM myself for about 2yrs now, just want to share my finding and experience as a reference or future research.

1. i see people mention after MM you have to richen the H setting because there is more air flowing in. i disagree, i read alot of posts here in this site before figuring it out. i also believe i might have same idea as Chris PA in 1 of his post, when the air moves through the carb the venturi effect is always in place. the H setting is the fuel to air ratio, once the ratio is set small change in air velocity will not make the saw run lean. as more fuel will follow(venturi effect)

2. but why does the saw still sound leaner compared to before MM ? i believe once the muffler is opened to certain point the saw runs lean because fresh air is pulled in through the new opening on the muffler during the scavenging effect. the piston downward travel creates a suction and the bigger muffler opening might allow more fresh air entry.

3. MM with tube moves peak power in the power band to lower side, somehow from my experience tube gives alot more broader power band and torque throughout the rpms. gutting and putting deflector moves rpm higher and makes more power at higher rpm. this could be tube creating better laminar flow for the exhaust gas discharge


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## Ted Jenkins (Aug 7, 2017)

There is no substitute for displacement period. A smaller saw with a muffler mod will run stronger, better, cooler and with more authority. However if I would be caught with a saw without a spark screen most likely jail time. I take every precaution possible to avoid any fires and any infraction of the rules set forth by USFS and California State FS. So modding a muffler is not an option for me, but I certainly know how. Thanks


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## blsnelling (Aug 7, 2017)

Robin Wood said:


> 1. i see people mention after MM you have to richen the H setting because there is more air flowing in. i disagree, i read alot of posts here in this site before figuring it out.


I have seen the same. The L is almost always lean, but not the H like most people think.


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## Robin Wood (Aug 7, 2017)

TW did mention that opening up muffler somewhere close to 200% will cause idle issues. 

Now here's something interesting, i have a triple port 353 with 2 3/8ths tube welded on the top site each left and right. its got cold start idle problem, it dies off and i have to restart about 4~5 times if i dont hold the throttle. but it idles absolutely fine when warm.

To prove my theory what i did was, when cold as soon as i start the saw i plug both the 3/8ths tube with my fingers. I held it as far as i can take the heat, guess what it idled without dying and the idle actually was abit higher.

I think when you open too much, the idling fuel gets dryed out by the more amount of air entering through the opening and causing the saw hard to stay in idle


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## Westboastfaller (Aug 7, 2017)

I think it effects the scavenging when you open it up as in true tuned pipe systems;
A "Smaller pipe when closest to the engine can also give more HP if tuned correctly as it have the ability to scavenge most efficient. When it's too big it won't scavenge properly resulting in hp loss as well idle g issues. 
I know its a can and not a pipe but you tamper with it too much and you will effect the pulse "waves"
Yours doesn't seem to be overly opened up to what he was describing though??

Got to think about it more?

I was thinking about your first post.
I'll get back on that.


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## Robin Wood (Aug 8, 2017)

Westboastfaller said:


> I think it effects the scavenging when you open it up as in true tuned pipe systems;
> A "Smaller pipe when closest to the engine can also give more HP if tuned correctly as it have the ability to scavenge most efficient. When it's too big it won't scavenge properly resulting in hp loss.
> I know its a can and not a pipe but you tamper with it too much and you will effect the pulse "waves"
> Yours doesn't seem to be overly opened up to what he was describing though??
> ...



i think for tuned pipe smaller size will give more pressure during the scavenging cycle and it could give better supercharging effect and could mean increase in compression as well. but you might lose volume if the pipe size is not matched correctly with the cc range.

for canned type muffler i think its actually more complicated to determine how the exhaust gas reacts with new opening, size, location and etc. i think with more or bigger opening the scavenging zone is increased for canned muffler, so air fuel mix travels abit more closer to the exit than its used to in stock form. which could explain the temperature decrease and poor fuel economy when overly done.

i did mine based on the flange size and found out its suppose to be exhaust port size like TW mentioned here, mine's at 150% with 2 tubes. 1/2" length that sticks in and out the muffler. its the sickest sounding saw i've seen or own, its got the old muscle cam overlap sound at idle. my jaw dropped when i did timed cuts, it went from about 11+secs to 8 secs flat. what i cant believe was, stock it will stall in the cut with medium pressure in 14" hardwood. now its quite hard to even make it bog with bar fully buried in hardwood even if i lever it hard. its like a different cc saw, i will make the idling video when im free


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## Westboastfaller (Aug 8, 2017)

Robin Wood said:


> TW did mention that opening up muffler somewhere close to 200% will cause idle issues.
> 
> Now here's something interesting, i have a triple port 353 with 2 3/8ths tube welded on the top site each left and right. its got cold start idle problem, it dies off and i have to restart about 4~5 times if i dont hold the throttle. but it idles absolutely fine when warm.
> 
> ...


 Its doing opposite what a cold saw should do. Sometimes mine will take as long as 30 sec to settle down with fast idle off. I have had and seen a lot of 357 and 372 not want to idle cold in the winter and many without MM. I presume you can idle up or jet In but you will have to move them back when it warm?

Ok your original theory was air enters through exhaust port more, this due to an enlarged MP/ports,, this being your reasoning for the leaner behavior.
Now with the second post the revs come up when you plug the modded ports and you offered a theory. Ineresting now to start off cold again but turn throttle up a bit before hand so it idles good then plug the ports again...maybe try some leather gloves. If it can idle fine then according to your first theory the revs should drop this time?
Some food for though?
Just wondering ...you have tried different carbs..cleaned it out and all what could reasonable be done? Sounds pretty hot runs strong otherwise.
I had a Walkerized 357 with triple port 266 deflectors on. Just the way they torched out the baffle and torched the pipe off. I would hold it at about 1/8-1/4 thottle and it would hold at a real lumpy rumple and I would just crack it Just before i layed into some bush. Then back to the rumble. Sounded like a piped snowmoble. Just the way the flow would hit the jagged metal and hit the torched pipe at an angle

I agree, understanding of a tuned pipe is relatively easy to grasp. It's Calculated and the travel creates a positive presure
You can't get that effect from the can
Different animal.


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## Robin Wood (Aug 8, 2017)

Westboastfaller said:


> Its doing opposite what a cold saw should do. Sometimes mine will take as long as 30 sec to settle down with fast idle off. I have had and seen a lot of 357 and 372 not want to idle cold in the winter and many without MM. I presume you can idle up or jet In but you will have to move them back when it warm?
> 
> Ok your original theory was air enters through exhaust port more, this due to an enlarged MP/ports,, this being your reasoning for the leaner behavior.
> Now with the second post the revs come up when you plug the modded ports and you offered a theory. Ineresting now to start off cold again but turn throttle up a bit before hand so it idles good then plug the ports again...maybe try some leather gloves. If it can idle fine then according to your first theory the revs should drop this time?
> ...



yes you are correct, if i turn in the idle it will idle right when cold but will start spinning the chain warm. the L jet expands once warm and let more fuel in which allows it to idle right ?

maybe i didnt put it in words correctly earlier. well the revs doesnt come high it just stays at the right idle like it is when warm, lets just say it idles like it should like a stock saw. this part is very tricky because at idle the gas expulsion rate is slow and alot factors can come in place. but you gave me a good idea, will try plugging the opening like you said. if im following you correctly, when i plug my fingers with idle turn a tad in it should be richer and the idle should drop ?

the saw is just 4 months old so carb and everything else is in good stock form. yeah that lumpy sound is sick, i could listen to that all day.

the turbulence in can muffler is unpredictable, gas expulsion rate reacts differently at different rpm.


very hard to figure, but when i found that saws being offered in different region with different muffler configuration i knew something was up. i've yet to see the deflectors you guys mod with in my country, not even AM mufflers with deflector. husky saws all come with the tube version. 288, 395, 372 and many others. i did my degree in manufacturing engineering, i can bet manufacturers will not do this unless there is some substantial difference. the added manufacturing, storage, tooling and etc cost will be quite a sum. from a manufacture standpoint of view, deflector should be more cost effective ? maybe the tube mufflers give more torque for the hard wood timber cutting going on here. while you guys got the high revving deflector type mufflers


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## Chris-PA (Aug 8, 2017)

Every 2-stroke will lose some of it's incoming fuel/air charge out the open exhaust port when the transfers open, and will pull some air back in the open exhaust port before the transfers close. With some sort of semi-enclosed chamber on the exhaust outlet then some of that lost fuel is still sitting outside the port, so what gets pulled back in contains more exhaust and some of that unburned fuel. 

At the other extreme with a wide open exhaust (no muffler), then the fuel that goes out is lost to the atmosphere, and what gets draw back into the cylinder before the port closes contains more oxygen. Any _fresh _air pulled into the combustion chamber through the exhaust does not pass through the carb and does not pick up any fuel, so it will lean the mixture by definition. You can tune that out, and clearly it will make the most power this way, but efficiency goes way down (due to the lost fuel). Also, it is likely to be less stable in terms of mixture control - there are two paths to get air trapped into the cylinder, one through the carb, intake, case and transfers, and the other through the exhaust. You are trying to add extra fuel into the fuel path to compensate for the raw air that comes in the exhaust, and if anything changes that balance the mixture will be wrong. That's why my muffler mods have always been mild (in addition to the noise issue). 

On a cold engine some of the fuel does not vaporize and stays in droplets that don't burn, so the mixture leans out and some sort of choke/enrichment system is needed. If it's not on choke when the engine is cold it will be a little lean. I can imagine that when the engine is cold the relationship between the amount of air entering the chamber from the exhaust port vs. the case might be different too on a cold engine.


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## Robin Wood (Aug 8, 2017)

Chris-PA said:


> Every 2-stroke will lose some of it's incoming fuel/air charge out the open exhaust port when the transfers open, and will pull some air back in the open exhaust port before the transfers close. With some sort of semi-enclosed chamber on the exhaust outlet then some of that lost fuel is still sitting outside the port, so what gets pulled back in contains more exhaust and some of that unburned fuel.
> 
> At the other extreme with a wide open exhaust (no muffler), then the fuel that goes out is lost to the atmosphere, and what gets draw back into the cylinder before the port closes contains more oxygen. Any _fresh _air pulled into the combustion chamber through the exhaust does not pass through the carb and does not pick up any fuel, so it will lean the mixture by definition. You can tune that out, and clearly it will make the most power this way, but efficiency goes way down (due to the lost fuel). Also, it is likely to be less stable in terms of mixture control - there are two paths to get air trapped into the cylinder, one through the carb, intake, case and transfers, and the other through the exhaust. You are trying to add extra fuel into the fuel path to compensate for the raw air that comes in the exhaust, and if anything changes that balance the mixture will be wrong. That's why my muffler mods have always been mild (in addition to the noise issue).
> 
> On a cold engine some of the fuel does not vaporize and stays in droplets that don't burn, so the mixture leans out and some sort of choke/enrichment system is needed. If it's not on choke when the engine is cold it will be a little lean. I can imagine that when the engine is cold the relationship between the amount of air entering the chamber from the exhaust port vs. the case might be different too on a cold engine.



that fuel droplet theory is quite interesting, its possible. and you are spot on how it works running without muffler.

what do you think the difference would be in a tube vs deflector muffler ? in terms of power, rpm and response


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## Chris-PA (Aug 8, 2017)

Robin Wood said:


> what do you think the difference would be in a tube vs deflector muffler ? in terms of power, rpm and response


I'm not really sure, and I suspect there are more variables than that. For example the relationship between the outlet style and a spark screen (if any). I don't like most of the modern designs with a tiny screen perched on the outlet, because the area is too small. Other designs have a large area screen internal, which works better with an outlet tube. Of course if there's no screen that's irrelevant. 

On my muffler mods I've always tried to make the flow travel the longest path internally while reducing restriction, in order to prevent mixing with external atmosphere as long as possible (and to reduce noise). I suppose an outlet tube helps do that too. I'm trying to increase the air flow/volume/velocity through the carb, but not pull more air in through the exhaust. In general, if I have to enrich the H I know I've opened it too far.


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## Robin Wood (Aug 8, 2017)

i find tube muffles the noise alot better than gutting.

if you are looking to get increased airflow through the carb and restrict airflow through the exhaust. my personal take is to open 2 or 3 small openings rather than 1 very big opening


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## BGE541 (Aug 9, 2017)

Seems like a lot assume or think a muffler mod means you can't run a spark arrestor. Here the req is .0014" stainless mesh on federal land, which does not seem to make a bit of difference if you mod the muffler appropriately.


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## Westboastfaller (Aug 9, 2017)

Robin Wood said:


> yes you are correct, if i turn in the idle it will idle right when cold but will start spinning the chain warm. the L jet expands once warm and let more fuel in which allows it to idle right ?


What is YOUR definition of warm? A bit of revving or is it cutting wood and getting heat into it?

The carb temperature shouldn't really get warmer In use. It should stay the temperature of the air blown opon it.
If you would like to clear any doubt about contraction/expansion in the orifice then put a hair dryer ...er...um I mean heat gun on the top of the carb for a sec then start it. You will get your answer.






Robin Wood said:


> maybe i didnt put it in words correctly earlier. well the revs doesnt come high it just stays at the right idle like it is when warm, lets just say it idles like it should like a stock saw. this part is very tricky because at idle the gas expulsion rate is slow and alot factors can come in place. but you gave me a good idea, will try plugging the opening like you said. if im following you correctly, when i plug my fingers with idle turn a tad in it should be richer and the idle should drop ?


Yes we are on the same page. I took it as that. Maybe top idle revs don't change but if the bigger port fluctuates down ...She stalls.

Yes that's what I'm saying you are basically double checking your 'math'
If it works one way it should work opposite the other..or we are going to find out why.....I have a feeling...lol
You should at least see differences when it's warm.
It seems you proved it doesn't run probably cold with that percent of opening.
Between your findings and my extreme cold experience leads me to believe the difference may be the ignition temp, less expansion in cold volumed air molecules,
inability to clear the extra emmisions on cold starts







Robin Wood said:


> the saw is just 4 months old so carb and everything else is in good stock form. yeah that lumpy sound is sick, i could listen to that all day.
> 
> the turbulence in can muffler is unpredictable, gas expulsion rate reacts differently at different rpm.


Nothing like the old school pipes
Pretty cool that they make then out of round stock from factory. Obviously it is better. Bob Walker, Walkerized saws former World Campion Race SAW Builder always used triple port with pipe horns on all his worK saws. The deflectors was a taimed down look as they have been working side by side with WCB for 25 yrs.
Initially they was a noise issue. It's a Grey area here in BC as are mod saws so we have to make them more natural looking.

I would have to say from '89 to prevent, I have done very well will Husqvarna. Never have warmed up to Zama carbs.
I believe one of their early Introductions was on the 365 that didn't go that well then they switched bach to Wardro.





Robin Wood said:


> the turbulence in can muffler is unpredictable, gas expulsion rate reacts differently at different rpm.


Temps ect...
The cross scavenging engine style is also unpredictable as it's ability to do just that
Is limited to low Rpm.. I always liked the dome piston it aids in the process acting as a deflector.


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## bikemike (Aug 9, 2017)

Robin Wood said:


> i think for tuned pipe smaller size will give more pressure during the scavenging cycle and it could give better supercharging effect and could mean increase in compression as well. but you might lose volume if the pipe size is not matched correctly with the cc range.
> 
> for canned type muffler i think its actually more complicated to determine how the exhaust gas reacts with new opening, size, location and etc. i think with more or bigger opening the scavenging zone is increased for canned muffler, so air fuel mix travels abit more closer to the exit than its used to in stock form. which could explain the temperature decrease and poor fuel economy when overly done.
> 
> i did mine based on the flange size and found out its suppose to be exhaust port size like TW mentioned here, mine's at 150% with 2 tubes. 1/2" length that sticks in and out the muffler. its the sickest sounding saw i've seen or own, its got the old muscle cam overlap sound at idle. my jaw dropped when i did timed cuts, it went from about 11+secs to 8 secs flat. what i cant believe was, stock it will stall in the cut with medium pressure in 14" hardwood. now its quite hard to even make it bog with bar fully buried in hardwood even if i lever it hard. its like a different cc saw, i will make the idling video when im free


I love the chit out of my 49cc piped echo clamshell saw good strong runner and holds nice rpm in the cuts very responsive on the throttle too


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## Chris-PA (Aug 9, 2017)

Robin Wood said:


> i find tube muffles the noise alot better than gutting.
> 
> if you are looking to get increased airflow through the carb and restrict airflow through the exhaust. my personal take is to open 2 or 3 small openings rather than 1 very big opening


I think the sound level and all the flow characteristics of the muffler are related. Ideally you'd want a muffler that took in all the pulsations from the exhaust port and had an outlet that just emitted the average flow without any pulsations at all. There would be no flow back into the exhaust. In practice that's not really possible, especially with small can sizes. Look at what it takes to make a quiet car exhaust, which usually has multiple stages, and it still ends up restricting the flow to some extent. Also, the acoustic and filtering characteristics of the muffler are fixed, while the engine fundamental rpm changes quite a bit, so it can never really match everywhere.

Essentially the muffler is analogous to a passive low pass filter, which will always have some restriction (loss) in addition to whatever filtering it is doing.

It's possible using multiple smaller outlet holes could help block some of the lower frequency pulsations compared to a single outlet with equivalent effective area, but this will depend on a lot of other things about how the muffler is constructed. Is is a single large can or does it have other internal baffles? It might be that an internal baffle has already reduced those frequencies, and then the multiple outlet holes won't matter much. I've done both single and multiple outlets, it depends on the rest of the design.


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## Robin Wood (Aug 9, 2017)

Chris-PA said:


> [QUOTE="Robin Wood, post: 6321033
> i find tube muffles the noise alot better than gutting.
> 
> if you are looking to get increased airflow through the carb and restrict airflow through the exhaust. my personal take is to open 2 or 3 small openings rather than 1 very big opening


I think the sound level and all the flow characteristics of the muffler are related. Ideally you'd want a muffler that took in all the pulsations from the exhaust port and had an outlet that just emitted the average flow without any pulsations at all. There would be no flow back into the exhaust. In practice that's not really possible, especially with small can sizes. Look at what it takes to make a quiet car exhaust, which usually has multiple stages, and it still ends up restricting the flow to some extent. Also, the acoustic and filtering characteristics of the muffler are fixed, while the engine fundamental rpm changes quite a bit, so it can never really match everywhere.

Essentially the muffler is analogous to a passive low pass filter, which will always have some restriction (loss) in addition to whatever filtering it is doing.

It's possible using multiple smaller outlet holes could help block some of the lower frequency pulsations compared to a single outlet with equivalent effective area, but this will depend on a lot of other things about how the muffler is constructed. Is is a single large can or does it have other internal baffles? It might be that an internal baffle has already reduced those frequencies, and then the multiple outlet holes won't matter much. I've done both single and multiple outlets, it depends on the rest of the design.[/QUOTE]

man you just brought the discussion to whole new level. i have no idea what you just said lol. but rock on bro.

this is a diferrent league now.

@westboasfaller that hair dryer trick will definetely clear my doubt, awesome idea buddy


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## Robin Wood (Aug 10, 2017)

@Westboastfaller

i took out my 353 for some quick fellings
was in a hurry but i did the hot pipe plugging test. you were right dude the idle came up, almost high enough to spin the chain intermittently

what does that mean ?
must be something

i dont have time to goof around, im sitting for my ISA arborist exam this sunday. the questions are based on temperate climate -__-, i hope i dont get shafted. wish me luck, will be back soon


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## Westboastfaller (Aug 10, 2017)

Robin Wood said:


> TW did mention that opening up muffler somewhere close to 200% will cause idle issues.
> 
> Now here's something interesting, i have a triple port 353 with 2 3/8ths tube welded on the top site each left and right. its got cold start idle problem, it dies off and i have to restart about 4~5 times if i dont hold the throttle. but it idles absolutely fine when warm.)
> 
> ...





Robin Wood said:


> @Westboastfaller
> 
> i took out my 353 for some quick fellings
> was in a hurry but i did the hot pipe plugging test. you were right dude the idle came up, almost high enough to spin the chain intermittently
> ...


Awesome, definitely all my best Robin!
I may be doing mine soon and start getting more into the consulting/riparian prescriptions. I'm addictied to cutting though. I'll have to have some side stuff to satisfy my need.

I originally said to Turn Up The Idle and start it then plug the mod ports right away When It Was Cold. On my second thought... was not to raise idle and to try plug TP warm as It would make for more conclusive testing considering the TP only had problems idling when on cold starts. (That's what you did right?)
*But I thought it would have done the opposite, that the revs would come down
Not up?
Let's do a recap
SP will idle cold
Sp the clutch wants to engage as it warms
TP stalls cold
TP idles warm


We both offered possibilities for the TP having difficulty running at an idle cold.
Had the idle dropped when plugging the TP when it was warm then it still would have left it as no closer that "it doesn't run well at that percent of exhaust opening" leaving our theories inconclusive.

I/We expected TP was having trouble ONLY cold for reasons given in pryor post. Revs came up with the TP when warm. Revs should have stayed the same with stock SP. ...meaning they would have needed to drop when plugging the warmed up TP.
Make sense...Or Are You AS Confused As I am?..lol

In a nut shell. The revs are comming up on the stock muffler as it warms up too.

*Why didn't I say that to begin with ???....that wouldn't be any fun*

So what does that mean you ask?
This saw hand says Properly running cold carberated engines don't run that way.
Revs drop down to idle when ready ...not come up. 
I'm basically back to my earlier thought again now after us 'exhausting' that avenue (bad pun I know)
It's a carb issue it would appear Robin.


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## Robin Wood (Aug 15, 2017)

Westboastfaller said:


> Awesome, definitely all my best Robin!
> I may be doing mine soon and start getting more into the consulting/riparian prescriptions. I'm addictied to cutting though. I'll have to have some side stuff to satisfy my need.
> 
> I originally said to Turn Up The Idle and start it then plug the mod ports right away When It Was Cold. On my second thought... was not to raise idle and to try plug TP warm as It would make for more conclusive testing considering the TP only had problems idling when on cold starts. (That's what you did right?)
> ...



thanks dude
you should, its really an eye opener. good info and gave me whole different level of understanding and troubleshooting in this field
im more of a transplant addict, sawing comes 2nd for me. but since its the most discussed stuff here might as well get used to it lol.
nothing beats the feeling of lifting something huge and with heavy equipments with the level of planning and precision involved
and bringing it elsewhere while everyone looks in awe. not to mention the nail biting moment to see if it survive. i like the adrenaline

i havent done that yet
but yes thats what happened like i described

revs come up when TP plugged when hot
yes our expectation was total opposite
and yes im as confused as you are or even more !!! lol

its not carb issue, the saw is pretty new. it runs fantastic
we are meddling with air movement here, so any change in direction/volume/velocity
will create a butterfly effect, it could be when TP is plugged more exhaust gas could be going inside the chamber
and making the combustion lean ? when TP is open the gasses are out and more mix is being scavenged back into the chamber ?
in return producing the exponential power gain, it is simply nuts. i cant imagine how it will run if its ported and gasket delete


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