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Dual port muffler.


colwoodlandcare
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Been looking at possible buying a dual port exhaust for the 660.

Does it give it any difference in power at all, or just sound?

 

 

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Colwood - Home

 

Stihl quoted 0.4 HP between the Magnum and the standard 066, the dual port is part of the difference in build.

 

You will get more power and torque from fitting it.

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Been looking at possible buying a dual port exhaust for the 660.

Does it give it any difference in power at all, or just sound?

 

 

Sent using Arbtalk Mobile App

Colwood - Home

 

Bit more power bit more torque and a bit cooler running . Best combined with a porting job . :001_smile:

Edited by Stubby
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This is a snippet from a thread Timberwolf of AS posted a few years back where he modified an MS260 in stages and took down some data. I found it very interesting, especially the heat part. Most saws have very tiny exhaust outlets. I am not surprised they cause the motor itself to heat up:

 

The muffler modification entailed 5 steps.

 

1 stock

2 stock muffler redrill existing outlet to 7/16 and add one 7/16 hole

3 add one more 7/16 hole

4 join 3 holes and square opening to 7/16 x 1.5 inch plus file back and open deflector angle.

5 match exaust port to muffler

 

The test consisted of the folowing steps

 

1 measure temp with saw cold roughly 7 degrees C

2 start and idle saw for 2 min monitor temp until stable

3 measure idle sound level

4 cycle saw to full RPM 5 times and record max sound and rpm

5 cycle saw between idle and full rpm for 1 min and measure temp

6 cut 3 disks and measure temp

7 allow saw to cool befor next test

 

AND HERE IS WHAT I FOUND

-----------------------------------

 

Stock muffler opening 0.11 sqr inches

---------------------------

 

RPM 13450

Idle sound level 80.2 db

Max sound level 97.1 db

Idle temp muffler 64 C

Idle temp head 60 C

Cycle test temp muffler 119C

Cycle test temp head 68C

3 cut test temp muffler 183C

3 cut test temp head 105C

3 cut test time 8.5 sec

 

 

Muffler with two 7/16 openings total 0. 30 sqr inch

---------------------------------------

 

RPM 13650 +1.5%

Idle sound level 84.9 db +5.9%

Max sound level 99.5 db +2.8%

Idle temp muffler 62 C -3.2%

Idle temp head 58 C -3.4%

Cycle test temp muffler 89C -33.7%

Cycle test temp head 62C -9.7%

3 cut test temp muffler 164C -11.6%

3 cut test temp head 96C -9.4%

3 cut test time 8.0 sec -6.3%

 

Muffler with three 7/16 openings total 0.45 sqr inches

-----------------------------------------

 

RPM 13750 +2.2%

Idle sound level 87.1 db +8.7%

Max sound level 101.8 db +4.8%

Idle temp muffler 56 C -14.3%

Idle temp head 55 C -16.4%

Cycle test temp muffler 88C -35.2%

Cycle test temp head 62C -9.7%

3 cut test temp muffler 147C -24.5%

3 cut test temp head 105C -12.9%

3 cut test time 7.6 sec -11.8%

 

Muffler with one 7/16 x 1.5 inch opening total 0.66 sqr inches

--------------------------------------------------

 

RPM 14000* +4.1%

Idle sound level 89.9 db +12.1%

Max sound level 103.0 db +6.1%

Idle temp muffler 54 C -18.6%

Idle temp head 52 C -15.4%

Cycle test temp muffler 82C -45.2%

Cycle test temp head 61C -11.5%

3 cut test temp muffler 143C -28.0%

3 cut test temp head 85C -23.6%

3 cut test time 6.9 sec -24.6%

 

* mixture richer by a hair RPM = 14100 before adjustment

 

Exaust port matched and smoothed

---------------------------------------------

 

RPM 14050 +4.4%

Idle sound level 89.9 db +12.1% NC

Max sound level 103.0 db +6.1% NC

Idle temp muffler 54 C -18.6% NC

Idle temp head 51 C -17.6%

Cycle test temp muffler 82C -45.2% NC

Cycle test temp head 61C -11.5% NC

3 cut test temp muffler 143C -28.0% NC

3 cut test temp head 83C -26.5%

3 cut test time 6.7 sec -26.8%

 

Discs were 12" spruce. He also stated, "...gains don't seem to be falling off too fast so I will likely open up the muffler a wee bit more in the future."

Edited by wyk
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