Zen and The Art of Chainsaw Modification

[skwerl]

TW, you say the saw is 7% less efficient since modding. Will you return it to stock in order to regain your lost efficiency?

 

[timberwolf]

Skwerl, I am thinking not, I will pay for the 7% on the gas bill to save 38% on the labor bill!

I am surprised it made that much difference, I knew th 359 was choked down with that muffler, but I did not know how much.

 

[Crofter]

So 7% less fuel efficient but 38 % more time efficient. Even at minimum wage the time is far more valuable. I knew they emptied the tank quicker. Now I wonder what further decrease in fuel efficiency would come from engine modifications? I am guessing decrease in cut times would be a further 25 % It will be nice to see a workup of all the figures on fuel consumption and cut times from stock to ? Are you going to make the trip to Haliburton or are you going to meditate some more? OMMMMMM............

 

[buck futter]

muffler mod details

TW,
when you gutted the muffler did you leave the pipe in? The only thing I did to mine was drill some larger holes in the baffle/plate inside. In your last test did you compare the gutted muffler to the one with the extra hole for cut times?
Where did you put the extra hole, in the middle of the bracket that holds the muffler on? How did you come up with the .61 sq. inch size for the additional hole? I calculated the exhaust port size at the cylinder wall to be .4861 sq. inches.
Thank you for this thread, I like the way you collected your data and of course the time and effort you put in.

What size bar and what type of chain did you have stock? How long have you run this saw, is it fully broken in? Do you plan on modding the jug, if so what are your plans?

Thanks
Lucky

 

[timberwolf]

I did not gut the muffler, just extended the openings back into the rear part, I left the pipe in, it looked to be too much of a pain to cleanly remove without cuting the muffler in two and rewelding, I went with 2 3/4 pipes with a 5/8 inch inside diamiter each. Spent a lot of time deburring and geting all the metal shavings out.

I guess my approach was a bit different than many who gut the muffler and put a centered hole in the front of the cover. I an not saying it is any better or worse in any way, just going on a hunch of how gas moves in the muffler and the impact it has on scavanging. I may test it some time on a 2 piece muffler that is easier to deal with.

 

[rahtreelimbs]

I did not gut the muffler, just extended the openings back into the rear part, I left the pipe in, it looked to be too much of a pain to cleanly remove without cuting the muffler in two and rewelding, I went with 2 3/4 pipes with a 5/8 inch inside diamiter each. Spent a lot of time deburring and geting all the metal shavings out.

I guess my approach was a bit different than many who gut the muffler and put a centered hole in the front of the cover. I an not saying it is any better or worse in any way, just going on a hunch of how gas moves in the muffler and the impact it has on scavanging. I may test it some time on a 2 piece muffler that is easier to deal with.

Howabout a few pics!!!

 

[timberwolf]

Here is a shot of the muffler, no nice paint job yet.

 

[OilHead]

Dispelling myths about opening up mufflers.

Here is a shot of the muffler, no nice paint job yet.

Those are certanly some impressive #s . For a 59cc engine two 5/8" exits must equate to at or near 100% of the exhaust port at the cylinder. I recently did a mod on a MS310 muffler for a friend, 59cc same as what you got there & the 361. Only went with 2 -1/2" exits looks like could have gone a lot more. Have you had a chance to check the pop off pressure ? I beleive you were one of the few on that thread that was going to look into it.

 

[timberwolf]

I messed with pop off preasure on it, forget now what the pressure was, even made a device to change pop off pressure depending on engine RPM... Never found much of any gain. Unless moddifying a carb for alcohol or going to extreme changes to the venturri I don't bother messing with the pop off.

 

[romeo]

Modding saws is like making music, I approach them both with the same frame of mind. Only 7 notes but a million ways to play them. Sometimes you have to be technically perfect and sometimes you just improvise, but the end result is all that really matters. Both go good with beer.



Does it rock?:rockn: Does it cut?:greenchainsaw: