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Anyone have any tips or places to look for info on modding the 192?
Chris
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Hey Chris, it really depends on what you want to do with the saw. If you want a simple mod that you can do with a "dremel" then just measure the area of the exhaust port at the cylinder. In other words, pull off the muffler, get some calipers and measure the dimensions of the exhaust port. It's oval shaped, so you'll have to estimate a bit.
Once you're confident you have the area measured accurately, then you'll want to open up the muffler and take out any internal baffles. Then, make the opening of the muffler about 85% of the area of the exhaust port.
So, if the exhaust port is 200 square millimeters (10mm x 20mm) then make the muffler opening 170 sq. mm.
You can go bigger than this, maybe even up to 125% of the exhaust port size but then the problem becomes that the noise level goes up quite a bit. If you're at all concerned about being able to hear your groundmen yelling at you while the saw is running, it might be best to go with the 85% value first to see how that noise level affects work place safety.
Going forward from a simple muffler mod requires measuring port timing, squish and spark advance to see how these things can be optimized without sacrificing longevity.
One thing is for sure, more power means more fuel consumption, so you'll be sending the saw down from the tree to be refueled more frequently, but then maybe the quicker cuts will compensate for that? I don't think anyone has done a controlled study to measure these effects.
Bob
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Chris, there's no baffles in a 192 muffler, and, if there were, you couldn't access them short of cutting the can open.
I hog out the inner hole, then, open the deflector by grinding the inner edge, and the outer as much as I can and still have the gases deflecting somewhat downward. Then, bend the outer edge out a bit as well. Gains will be about 20%.
On both of my modded ones, I ground tne inner hole all the way to its edges, as the deflector is the real limiter. But, the deflector screw sometimes rattles out, and the deflector is lost. This makes the saw too loud, but even faster. Even though the hole size ratio is way too large, it's clear that the reduced back pressure is not limiting power. But the noise is excessive. Just need to lightly weld that screw to lock it.