Skip the muffler all together

[3000 FPS]

I believe it was Timberwolf that did some pretty exstensive testing on muffler mods and how much opening of the muffler affected the performance. I believe he said that after a certain point that maintaining an idle at a lower rpm was difficult to keep the saw running and that after 120% of the exhaust port all that was to be gained was about another 5% in performance.
It was one of the best tests of a real saw and checked results that I have read so far. Not just a bunch of theory.

 

[TBone0106]

Since this thread has actually brought out some discussion of 2 stroke exhaust tuning, I'll post this two stroke tuning guide for you guys to chew on for a while. It is old school, but all the tuning perimeters are still basically the same. Enjoy. And make sure you check out the #1 fan!!!!

Two Stroke Tuners Handbook

ZOWIE!!! Serious reference material! Mega-thanks!

Still, I look at Ol' Blue, my 1960-something XL-12, and wonder how that little vented-stack "muffler" could actually be doing anything at all beyond protecting the cylinder and the piston from whatever debris might come their way. For sure, these old-style "mufflers" had nothing against noise. I haven't tried it, but I'd be willing to bet that Ol' Blue would start and run just as well -- and as loudly -- without that "muffler" as it does with it. I used to run similar vintage Remingtons -- SL4's mostly -- that had similarly useless mufflers. For a fact, I ran one of those Remingtons without any muffler for days before a stray something got into the cylinder and caused... well, a problem.

Still, THANKS for the excellent reference!

 

[Dan_IN_MN]

A couple of years ago at Grandpatractors GTG, treemonkey had his 026 there. Percentage of how much a muffler could be opened up became the topic. He came out of Grandpatractors shop with the 026 and no muffler at all. In the cut, I could see the piston moving up an down in the exhaust port. I don't recall how the saw ran. Perhaps others can fill in the missing details. I know it was loud! I think it cut well. I don't believe idling was even considered as an option!

I realize this saw is a reed valve intake, I remember the old Sears (David Bradley) basically had an open port exhaust having slits for a muffler.

 

[sachsmo]

There's plenty of saws with front-exit mufflers in production. What I was talking about are the guys that chop the whole front of the muffler out, past the point of diminishing returns. Because it's so loud, they think "it has to run better." One local logger ended up spending $200 on new mufflers after modifying his with a bar wrench and a hammer.

JJ is a Pro, but if you never think outside the box?


I have done several muffler mods with the intention of being able to bring them back to stock appearing.

I suppose it will be frustrating for a restorer to find a unmolested muffler someday.

But when I got that 359 the topic was on how poorly they run with a cat muffler.

Got a new non-cat muffler, but after some examination found that it was trying to exhaust thru a 10mm I.D. straw.(tube)

The 5100 I had would out cut it. So that being my first muffler mod it was done with the thought of eliminating as much back pressure possible.

Right or wrong, it has been that way for 6 years, (the 5100 can't touch it now) here it was when it wore a screen;

 

[angelo c]

Not saying I'm right but many times when working on a saw, I'll pull it to see if I got some pop. Never at full power but just long enought to see if it runs. All without a muffler. No sense putting a muff on then taking it back off, before your sure its running right.

 

[sachsmo]

Ahh, you're a Hoosier, you don't have any of significance to get under :hmm3grin2orange::hmm3grin2orange::hmm3grin2orange:.

That'll get the yoopers going :yoyo:!

Yoopers are just squatters on sovereign Wisconsin soil eh?


Oh by the way I the Mighty Mac!

 

[Chris-PA]

This is an interesting topic and one I was thinking about a lot lot when I did my first muffler mod. Not that I make them very extreme, as I don't want them to be too loud - well, one is anyway! What I was worried about was the exhaust pulses pulling oxygen back into the cylinder and leaning the mixture, perhaps even just at local hot spots. This can happen on 4-strokes causing burned exhaust valves. OTOH, those things on old saw engines are barely more than pipes, of course they often had iron cylinder liners, ran lower rpm and probably were stinking rich all the time. So I dunno.

I think if you have a can and an outlet you are probably not going to pull much oxygen back into the cylinder, especially if there is a screen.

 

[3000 FPS]

This is an interesting topic and one I was thinking about a lot lot when I did my first muffler mod. Not that I make them very extreme, as I don't want them to be too loud - well, one is anyway! What I was worried about was the exhaust pulses pulling oxygen back into the cylinder and leaning the mixture, perhaps even just at local hot spots. This can happen on 4-strokes causing burned exhaust valves. OTOH, those things on old saw engines are barely more than pipes, of course they often had iron cylinder liners, ran lower rpm and probably were stinking rich all the time. So I dunno.

I think if you have a can and an outlet you are probably not going to pull much oxygen back into the cylinder, especially if there is a screen.

http://www.arboristsite.com/chainsaw/44816.htm Check out this old thread by Timberwolf and you will see running lean is not a problem.

 

[Chris-PA]

http://www.arboristsite.com/chainsaw/44816.htm Check out this old thread by Timberwolf and you will see running lean is not a problem.

Yeah, I've read through that thread before, it's a good one. Reducing the back pressure and increasing the air flow (velocity) will make the mixture richer, just because of how the carbs work - but naturally you should retune and correct that anyway. What I was thinking about is that if you had an open pipe then pressure waves will reflect back from the open end of the pipe, and it will carry back some air molecules with the return pulse. But in practice I don't really think this is a problem, especially with a can.

 

[leeha]

No muffler in this bad boy.
But it is loud as F%$#ck.


Lee

 

[edisto]

Ok,So then if a stock muff was opened to the 80% of the cylinder outlet then would less of the mix be burned and excape out the exhaust because of less back pressure? Or would the more flow because of the increased muff opening make up for this? I dont mean to sound like I am wanting to argue, I am interested in understanding this better.

2-strokes are an exercise in tradeoffs. If we pretend it was possible to keep the fresh charge and the spent charge from mixing, the ideal situation would be for the exhaust to close just as the last bit of combusted charge left the cylinder. Less back pressure would decrease the resistance to flow, and allow fresh charge into the exhaust port.

Because the charge mixes with the exhaust, the optimum shifts towards having some fresh charge enter the exhaust port, because the charge will be less diluted by exhaust. Modern saws are designed to minimize charge in the exhaust to cut down on emissions, so it is possible that less back pressure could improve performance by reducing dilution, but at the cost of fuel efficiency and increased emissions.

This has it's limitations as well, because there is a finite amount of charge that can be "pushed" into the cylinder from the crankcase, so at some point the advantages of less dilution are offset by lower charge density.

The more recent strato saws try to effect a compromise by using air instead of charge to scavenge the cylinder of exhaust gasses, so dilution by spent gasses is minimized, as is the loss of fresh charge into the exhaust port.

 

[TermiteBuffet]

No muffler in this bad boy.
But it is loud as F%$#ck.


Lee

I always drool all over the keyboard when i see that saw..... that is as cool as they come

 

[Herdbull]

So then this is bad........:cool2:

 

[edisto]

Has anyone ever tried skipping the muffler all together? A fire hazard is the only reason I could see a person not doing this. Wouldn't be an issue if you are cutting in the pouring rain.

Just remember, the best modification is a sharp chain...

 

[ziggybyrne]

You've got the basics. It has been tested and, generally, it will not work. There are, of course exceptions.

This saw is about as close to an open exhaust as you can get, but it is also fed by a carb that can move enough fuel to keep up.


View attachment 268969

Where on earth did you get that muffler? I want one for my 380A! What does it sound like?

 

[Dan_IN_MN]

So then this is bad........:cool2:

This is better! ****EDIT****NOPE! Not any bigger!

 

[sachsmo]

So then this is bad........:cool2:

You need to put that in the freaky muffler thread.

 

[sachsmo]

Didn't notice, put 'em both over there.

 

[Jacob J.]

I always drool all over the keyboard when i see that saw..... that is as cool as they come

Lee's custom creations are about as cool as can be. That saw looks like it's powered by testosterone, whiskey, and nitromethane.

So then this is bad........:cool2:

Not necessarily...

 

[old-cat]

Right out the front runs just fine.

View attachment 269012View attachment 269013

That is an absolutely awesome looking exhaust! I LIKE it!