Discussion in 'Work Safe' started by nitesite, Jun 27, 2020 at 1:14 AM.
You know. Just to open up the throttle some more.
Asking for a friend.......
I have not personally. I have seen competition chain saws that had expansion chambers in place of the muffler.
That muffler is probably a "mini" expansion chamber. An expansion chamber on a 2-stroke helps scavenge burned fuel-air out and draw new fuel-air in to the combustion chamber. About all you should do is clean any carbon buildup out of it...
Some chainsaws are more constricted than they need to be due to the .gov EPA standards. Because....
There are lots of ways to do a good 2-stroke muffler. They all resemble musical instruments, trumpets or horns, in how they flare. This is because they scavenge by resonance, and resonate by coupling the motion of moving gasses, to improve flow.
A muffler on a typical chainsaw is only roughly tuned, but it works OK across a broad band. It's not "peaky".
As you open the exhaust, the RPM sweet spot will rise, and the saw will cut faster there, IF the carb and reeds/ports can keep up. The power band may narrow, though peak power improves. Low torque is lost. The torque and HP curves came together at higher and higher RPM. At some point the engine will rev up faster and higher under no-load, but wont develop the same power under full normal load.
Then you must back off or do something else to increase flow. Bore the carb, open the ports, custom reeds, taller piston, OR better muffler geometry (#1 thing).
Now in practice, there are pesky manufacturing tolerances. If you get a machine where the tolerances line up favorably, that engine will be capable of more flow.
Look to the intake & especially exhaust port/gasket/muffler alignment and make them match as perfectly as possible. Not ported, but 100% smooth, polished and lightly relieved.
Then go after the muffler with a reamer, opening up the dozen or more existing holes slightly, and starting with ones farthest from the exhaust port.
If it has an internal screen, that must come out. They clog too fast. Put an external screen on to prevent sparks, if needed by law, and clean it when needed.
If you go too far and the saw runs worse, start closing up holes.
I didn't answer the original question after all that typing.
Yes. I removed the screen and opened the holes with a drill. I went too far, and closed one hole off with a screw, then was happy enough.
I just read a recommendation about doing this on a chainsaw forum, to home grade saws reach full potential
I loved that show.
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