Post by RBW on Feb 25, 2007 17:57:20 GMT -5
OK, as mentioned in a previous thread, these saws aren't as restrictive as todays EPA saws, but there is still some tricks you can do to make the muffler flow better and the saw in return run better.
Were going to start this mod by following the exhaust flow from the cylinder to the muffler outlet.
In this first pic you can see the exhaust port in the cylinder. While you have the muffler off you might as well inspect the piston and cylinder for any signs of wear or scoring. This saw has the thin rings which usually come on the higher performance (as in relation to their displacement) saws, and this saw while a homeowner saw is no exception.
This saw keeps up with some of its ancestors which have a larger displacement, once you remove the bottleneck in the muffler, keep reading and youl see what I mean.
OK, in this pic you can get a before and after look at the first baffle and how its modified. Gasses don't like to turn corners, and before this baffle is modded the exhaust gas comes out of the cylinder and slams into this plate and is forced to turn 90*, then it has to make another 180* turn through the large hole around the tube, to get to the exit tube. After the mod the exhaust has several directions it can go depending on how much flow there is.
If you look through the holes Ive made in the baffle you can see straight through to the green table beneath.
Now the gasses only have to make a single 180* turn to get out of the muffler rather than 2 90* turns and one 180* turn.
Next step deals with the exit tube. In its stock form the exit tube has a square edge that rests inside a fairly nice radiused flange in the baffle. The problem here is that the smooth flow over the radius of the flange gets interrupted by the square edge of the exit tube.
This is remedied by gently "Peening" the end of the tube into a sort of venturi shape with a nice radiused leading edge and then enlarging the hole where the original radiused flange was.
This makes for a smoother transition of the gasses into the tube.
Its hard to see in that pic due to the screen holding up the baffle but when everything is sandwiched together the edge of the hole in the baffle is just slightly above and directly centered over the edge of the radiused end of the exit tube.
This next and final pic shows the final obstacle that the exhaust has to deal with. As I mentioned, the exhaust leaves the exhaust port and makes a 180* turn through our modded muffler and goes out the back of the muffler Twords the cylinder.
This part of the mod is simply bending the shield outward in order to give the gasses a 4th escape route. I thought about doing more on this baffle but didnt want to put any of the exhaust heat back into the cylinder.
The last step in the mod is to retune the carb to deliver more fuel to compensate for the better flow through the saw.
There, now you have a happier, healthier and better cutting saw!
Were going to start this mod by following the exhaust flow from the cylinder to the muffler outlet.
In this first pic you can see the exhaust port in the cylinder. While you have the muffler off you might as well inspect the piston and cylinder for any signs of wear or scoring. This saw has the thin rings which usually come on the higher performance (as in relation to their displacement) saws, and this saw while a homeowner saw is no exception.
This saw keeps up with some of its ancestors which have a larger displacement, once you remove the bottleneck in the muffler, keep reading and youl see what I mean.
OK, in this pic you can get a before and after look at the first baffle and how its modified. Gasses don't like to turn corners, and before this baffle is modded the exhaust gas comes out of the cylinder and slams into this plate and is forced to turn 90*, then it has to make another 180* turn through the large hole around the tube, to get to the exit tube. After the mod the exhaust has several directions it can go depending on how much flow there is.
If you look through the holes Ive made in the baffle you can see straight through to the green table beneath.
Now the gasses only have to make a single 180* turn to get out of the muffler rather than 2 90* turns and one 180* turn.
Next step deals with the exit tube. In its stock form the exit tube has a square edge that rests inside a fairly nice radiused flange in the baffle. The problem here is that the smooth flow over the radius of the flange gets interrupted by the square edge of the exit tube.
This is remedied by gently "Peening" the end of the tube into a sort of venturi shape with a nice radiused leading edge and then enlarging the hole where the original radiused flange was.
This makes for a smoother transition of the gasses into the tube.
Its hard to see in that pic due to the screen holding up the baffle but when everything is sandwiched together the edge of the hole in the baffle is just slightly above and directly centered over the edge of the radiused end of the exit tube.
This next and final pic shows the final obstacle that the exhaust has to deal with. As I mentioned, the exhaust leaves the exhaust port and makes a 180* turn through our modded muffler and goes out the back of the muffler Twords the cylinder.
This part of the mod is simply bending the shield outward in order to give the gasses a 4th escape route. I thought about doing more on this baffle but didnt want to put any of the exhaust heat back into the cylinder.
The last step in the mod is to retune the carb to deliver more fuel to compensate for the better flow through the saw.
There, now you have a happier, healthier and better cutting saw!