Have any of you done a "muffler-mod" to your chainsaw?
- Thread starter nitesite
- Start date
I have not personally. I have seen competition chain saws that had expansion chambers in place of the muffler.
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.
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 loved that show.