Muffler Mod, ya think?

[hardpan]

I have read hundreds of threads and mentions here on muffler mods and particularly the ones from the AS saw builders/modders. The generous folks here share valuable information and I am thankful for their contributions. I hear recommendations to open the muffler outlet to 70 or 80% of the cylinder exhaust port. I have a MS362 that I like just fine stock because I have a good memory for the performance of the junk I ran for the 35 years before I stepped over the line to the pro saws. OK, call it CAD. So I was wondering just how choked up the 362 is? I took off the muffler and made a couple measurements. Now I can sometimes appreciate a tight hole but I was shocked at what I found. The cylinder exhaust port is 387 sq. mm and muffler outlet is 79 sq. mm. Yep, the muffler outlet is 20% of the exhaust port. I promptly ordered a 288XP deflector and screen from Baileys. I'm hopelessly conservative so I'm only going to 70% and that gain can be made with (2) 3/8" and (1) 5/16" holes or a simple rectangle 15mm X 18mm, etc. Of course I will retune.
What a deal. Better performance, runs cooler, cheap and easy fix. I might even feel the need to tinker with 346XP and the MS460.
A little math opened my eyes and now I wonder if this is extreme or is this restriction common with most of the new EPA saws. 20% sucks

 

[Ronaldo]

I have read hundreds of threads and mentions here on muffler mods and particularly the ones from the AS saw builders/modders. The generous folks here share valuable information and I am thankful for their contributions. I hear recommendations to open the muffler outlet to 70 or 80% of the cylinder exhaust port. I have a MS362 that I like just fine stock because I have a good memory for the performance of the junk I ran for the 35 years before I stepped over the line to the pro saws. OK, call it CAD. So I was wondering just how choked up the 362 is? I took off the muffler and made a couple measurements. Now I can sometimes appreciate a tight hole but I was shocked at what I found. The cylinder exhaust port is 387 sq. mm and muffler outlet is 79 sq. mm. Yep, the muffler outlet is 20% of the exhaust port. I promptly ordered a 288XP deflector and screen from Baileys. I'm hopelessly conservative so I'm only going to 70% and that gain can be made with (2) 3/8" and (1) 5/16" holes or a simple rectangle 15mm X 18mm, etc. Of course I will retune.
What a deal. Better performance, runs cooler, cheap and easy fix. I might even feel the need to tinker with 346XP and the MS460.
A little math opened my eyes and now I wonder if this is extreme or is this restriction common with most of the new EPA saws. 20% sucks

Measure the ms460........that opening will shock you as well. The several ms460's that I have opened up made a lot of difference!

 

[spindrift7mm]

Are you allowing for the screen ? You'll really find saws like a lot more than 70% if using spark screen. Open stock hole to max and the max size the 288 unit will cover works well. On my ported Stihls I max out the stock outlets on the dual port set up and add a left side outlet for triple port w/screens which is about maxed for a ported saw. Their loud !

 

[hardpan]

Are you allowing for the screen ? You'll really find saws like a lot more than 70% if using spark screen. Open stock hole to max and the max size the 288 unit will cover works well. On my ported Stihls I max out the stock outlets on the dual port set up and add a left side outlet for triple port w/screens which is about maxed for a ported saw. Their loud !

I was wondering about the screen reduction. My saws are not ported and I want to keep the screens. Sounds like I can go much bigger. Thanks.