Properly done mods (imho) will increase Air-flow thru the engine. More Air=More Torque which will translate into increased cutting speed. Flow and velocity are paramount as we are talking chainsaws which are direct drive with no gears. There are many porting schemes that work and it all depends on how far you want to go (machine work to tighten squish , widening ports ) and how long you want the saw to last( piped cookie cutter vs worksaw) By increasing torque you are also increasing HP and thereby increasing cut speed. An everyday worksaw that will increase cut speed by 20-25%+ over a stocker with minimal increase in fuel consumption AND have great longevity is what I want in a built worksaw , YMMV . A piped cookie cutter that will increase cut speed by 80% is a different kettle of fish.....Here’s a piped 660 that I built. Not a true “race saw build” by any means. I can remove the pipe, install muffler, retune carb and go cut wood and vice-versa, This saw could produce much faster cut times with additional work/tuning IF desired ....Thanks for such a thorough reply, very appreciated!!
- Re porting you refer to it as "Increasing cut-speed"....was that just a manner of speaking, or were you meaning to imply/explain that port jobs are more of a speed thing than a power / torque thing? I know they are related to a degree but am curious if you had more to say on this!
- 20-25% gain in cut speed (or torque/power)? That is most-definitely enough that I'd take on such a project (I don't wanna go buy a 60cc when I have a 40cc, but am not yet able to justify some 75-100cc saw, so if I can eek some more from my 40cc and put a 24" on it I'll be peachy for the next quarter year ;D )
- Re fuel-economy losses....I kinda see this two ways:
#1 - The relative fuel-economy of each configuration (IE, if the porting makes it go through fuel 20% quicker, am I also getting a 20% gain in power? Of course not, but if it's a 20% loss in fuel efficiency, for a 2.5% power gain, that's unacceptable...if it's a 20% gain for a 22% efficiency-loss, then that's basically just "turning-up the power"
#2 - Even if it's a pretty rough loss - say, 10% power-increase for 20% more fuel used - I don't necessarily see that as bad... Sometimes the MOST important thing is simply being sure the saw can push-through a cut (when cutting in-tree, to avoid the bar getting pinched, to ensure a log swings on a hinge the way you needed it, etc....my thinking has always leaned to the side of I'd rather just refill the tanks more often, honestly I rarely need a 2nd fill while aloft as I rappel down more often than most I would guess (as I solo rig most stuff so am always up&down as I work through something!)
Thanks again for such a thorough reply, think I may be able to embark on this mission (obviously this isn't a climbsaw, but I have a climbsaw I reallllllly wanted to port but just didn't want to risk trying on that machine, so kinda looking for a trial candidate, if I can get 15% power for a 20% fuel loss on my rear-handle that would work for me