Stihl 026 Muffler Mods?

[SteveSr]

I am considering opening the muffler on my 026 but had a few question that I was hoping some of you might be able to answer.

1. Has anyone done any quantatative testing either with timed cuts or a dyno to determine how much improvement can be obtained?

2. Are the mods done mostly on the inside of the muffler cover or does the outside have to be physically modified? I have seen some of the pictures posted on this site of brazed pipes on muffler covers and am wondering if this would be necessary.

3. Is the spark screen maintained with the modification or is it removed or bypassed? This saw sees periodic use in National Forests and I really don't want to be starting any fires or violating regulations so I would like to leave the screen.

The saw has the older 2 screw carburetor so any required mixture adjustments should be relatively easy. I am mostly looking for more power and reduced operating temperatures. I am not planning to do any modifications to the cylinder.

Thanks!

 

[glens]

There's http://www.arboristsite.com/showthread.php?action=showpost&postid=53547 (and it's thread) if you want to see some measured results with an 026.

I've been toying with formatting the data in a prettier package and am just about to submit it to the author of that post for his approval.

Glen

 

[SteveSr]

Glen,

Thanks for the pointer. This is exactly what I was looking for! Looks like everybody owes Timberwolf a real debt of gratitude for taking the time to do all of the testing.

I am wondering now if the noise issue has had more effect on muffler design than the EPA. I thought that they were adding catalytic converters to saws in places that had tighter pollution regulations. Oh, but the catalyst, if the same as in cars, requires higher temperatures to operate efficiently. So maybe it was a combination of both. Has anyone ever examined the difference between a cat muffler and a non-cat muffer?

 

[glens]

It's been more than 24 hours now since I'd emailed him and I've gotten no reply, nor has he even fetched the sample from my server, so I'm going to go ahead and post the tables here.

I've corrected the math and added a couple reference columns.  Everything should be self-explanatory except that I've used -10db = 50% and +10db = 200% of whatever reference level.

See his original post (link above) for the background info.  As part of the thread it'll be http://www.arboristsite.com/showthread.php?s=&postid=53547

Glen

<hr>

<center><table border="1" cellspacing="2" cellpadding="4"><caption> table 1 </caption> <tr><th width="240" colspan="2">Stock muffler opening 0.11 in<font size="-2">²</font></th></tr> <tr><td width="180">RPM</td><td width="60" align="right">13450</td></tr> <tr><td>Idle sound level</td><td align="right">80.2 db</td></tr> <tr><td>Max sound level</td><td align="right">97.1 db</td></tr> <tr><td>Idle temp muffler</td><td align="right">64&deg; C</td></tr> <tr><td>Idle temp head</td><td align="right">60&deg; C</td></tr> <tr><td>Cycle test temp muffler</td><td align="right">119&deg; C</td></tr> <tr><td>Cycle test temp head</td><td align="right">68&deg; C</td></tr> <tr><td>3 cut test temp muffler</td><td align="right">183&deg; C</td></tr> <tr><td>3 cut test temp head</td><td align="right">105&deg; C</td></tr> <tr><td>3 cut test time</td><td align="right">8.5 sec</td></tr> </table>

<br><table border="1" cellspacing="2" cellpadding="4"><caption> table 2 </caption> <tr><th width="240" colspan="2">Muffler with two 7/16 openings total 0.30 in<font size="-2">²</font></th><th align="center">change</th><th align="center">stock<br>value</th></tr> <tr><td width="180">RPM</td><td width="60" align="right">13650</td><td width="60" align="right">+1.5%</td><td width="60" align="right">98.5%</td></tr> <tr><td>Idle sound level</td><td align="right">84.9 db</td><td align="right">+38.5%</td><td align="right">72.2%</td></tr> <tr><td>Max sound level</td><td align="right">99.5 db</td><td align="right">+18.1%</td><td align="right">84.7%</td></tr> <tr><td>Idle temp muffler</td><td align="right">62&deg; C</td><td align="right">-3.1%</td><td align="right">103.2%</td></tr> <tr><td>Idle temp head</td><td align="right">58&deg; C</td><td align="right">-3.3%</td><td align="right">103.4%</td></tr> <tr><td>Cycle test temp muffler</td><td align="right">89&deg; C</td><td align="right">-25.2%</td><td align="right">133.7%</td></tr> <tr><td>Cycle test temp head</td><td align="right">62&deg; C</td><td align="right">-8.8%</td><td align="right">109.7%</td></tr> <tr><td>3 cut test temp muffler</td><td align="right">164&deg; C</td><td align="right">-10.4%</td><td align="right">111.6%</td></tr> <tr><td>3 cut test temp head</td><td align="right">96&deg; C</td><td align="right">-8.6%</td><td align="right">109.4%</td></tr> <tr><td>3 cut test time</td><td align="right">8.0 sec</td><td align="right">-5.9%</td><td align="right">106.3%</td></tr> </table>

<br><table border="1" cellspacing="2" cellpadding="4"><caption> table 3 </caption> <tr><th width="240" rowspan="2" colspan="2">Muffler with three 7/16 openings total 0.45 in<font size="-2">²</font></th><th rowspan="1" colspan="2" align="center">change</th><th rowspan="2" align="center">stock<br>value</th></tr> <tr><th rowspan="1" colspan="1" align="center">step</th><th rowspan="1" colspan="1" align="center">total</th></tr> <tr><td width="180">RPM</td><td width="60" align="right">13750</td><td width="60" align="right">+0.7%</td><td width="60" align="right">+2.2%</td><td width="60" align="right">97.8%</td></tr> <tr><td>Idle sound level</td><td align="right">87.1 db</td><td align="right">+16.5%</td><td align="right">+61.3%</td><td align="right">62.0%</td></tr> <tr><td>Max sound level</td><td align="right">101.8 db</td><td align="right">+17.3%</td><td align="right">+38.5%</td><td align="right">72.2%</td></tr> <tr><td>Idle temp muffler</td><td align="right">56&deg; C</td><td align="right">-9.7%</td><td align="right">-12.5%</td><td align="right">114.3%</td></tr> <tr><td>Idle temp head</td><td align="right">55&deg; C</td><td align="right">-5.2%</td><td align="right">-8.3%</td><td align="right">109.1%</td></tr> <tr><td>Cycle test temp muffler</td><td align="right">88&deg; C</td><td align="right">-1.1%</td><td align="right">-26.1%</td><td align="right">135.2%</td></tr> <tr><td>Cycle test temp head</td><td align="right">62&deg; C</td><td align="right">0%</td><td align="right">-8.8%</td><td align="right">109.7%</td></tr> <tr><td>3 cut test temp muffler</td><td align="right">147&deg; C</td><td align="right">-10.4%</td><td align="right">-19.7%</td><td align="right">124.5%</td></tr> <tr><td>3 cut test temp head</td><td align="right">105&deg; C</td><td align="right">-9.4%</td><td align="right">0%</td><td align="right">100.0%</td></tr> <tr><td>3 cut test time</td><td align="right">7.6 sec</td><td align="right">-5.0%</td><td align="right">-10.6%</td><td align="right">111.8%</td></tr> </table>

<br><table border="1" cellspacing="2" cellpadding="4"><caption> table 4 </caption> <tr><th width="240" rowspan="2" colspan="2">Muffler with one 7/16 x 1.5 inch opening total 0.66 in<font size="-2">²</font></th><th rowspan="1" colspan="2" align="center">change</th><th rowspan="2" align="center">stock<br>value</th></tr> <tr><th rowspan="1" colspan="1" align="center">step</th><th rowspan="1" colspan="1" align="center">total</th></tr> <tr><td width="180">RPM</td><td width="60" align="right">14000*</td><td width="60" align="right">+1.8%</td><td width="60" align="right">+4.1%</td><td width="60" align="right">96.1%</td></tr> <tr><td>Idle sound level</td><td align="right">89.9 db</td><td align="right">+21.4%</td><td align="right">+95.9%</td><td align="right">51.0%</td></tr> <tr><td>Max sound level</td><td align="right">103.0 db</td><td align="right">+8.7%</td><td align="right">+50.5%</td><td align="right">66.4%</td></tr> <tr><td>Idle temp muffler</td><td align="right">54&deg; C</td><td align="right">-3.6%</td><td align="right">-15.6%</td><td align="right">118.5%</td></tr> <tr><td>Idle temp head</td><td align="right">52&deg; C</td><td align="right">-5.5%</td><td align="right">-13.3%</td><td align="right">115.4%</td></tr> <tr><td>Cycle test temp muffler</td><td align="right">82&deg; C</td><td align="right">-6.8%</td><td align="right">-31.1%</td><td align="right">145.1%</td></tr> <tr><td>Cycle test temp head</td><td align="right">61&deg; C</td><td align="right">-1.6%</td><td align="right">-10.3%</td><td align="right">111.5%</td></tr> <tr><td>3 cut test temp muffler</td><td align="right">143&deg; C</td><td align="right">-2.7%</td><td align="right">-21.9%</td><td align="right">128.0%</td></tr> <tr><td>3 cut test temp head</td><td align="right">85&deg; C</td><td align="right">-19.0%</td><td align="right">-19.0%</td><td align="right">123.5%</td></tr> <tr><td>3 cut test time</td><td align="right">6.9 sec</td><td align="right">-9.2%</td><td align="right">-18.8%</td><td align="right">123.2%</td></tr> </table> &nbsp; * mixture richer by a hair RPM = 14100 before adjustment<br>

<br><table border="1" cellspacing="2" cellpadding="4"><caption> table 5 </caption> <tr><th width="240" rowspan="2" colspan="2">Exhaust port matched and smoothed</th><th rowspan="1" colspan="2" align="center">change</th><th rowspan="2" align="center">stock<br>value</th></tr> <tr><th rowspan="1" colspan="1" align="center">step</th><th rowspan="1" colspan="1" align="center">total</th></tr> <tr><td width="180">RPM</td><td width="60" align="right">14050</td><td width="60" align="right">+0.4%</td><td width="60" align="right">+4.5%</td><td width="60" align="right">95.7%</td></tr> <tr><td>Idle sound level</td><td align="right">89.9 db</td><td align="right">0%</td><td align="right">+95.9%</td><td align="right">51.0%</td></tr> <tr><td>Max sound level</td><td align="right">103.0 db</td><td align="right">0%</td><td align="right">+50.5%</td><td align="right">66.4%</td></tr> <tr><td>Idle temp muffler</td><td align="right">54&deg; C</td><td align="right">0%</td><td align="right">-15.6%</td><td align="right">118.5%</td></tr> <tr><td>Idle temp head</td><td align="right">51&deg; C</td><td align="right">-1.9%</td><td align="right">-15.0%</td><td align="right">117.6%</td></tr> <tr><td>Cycle test temp muffler</td><td align="right">82&deg; C</td><td align="right">0%</td><td align="right">-31.1%</td><td align="right">145.1%</td></tr> <tr><td>Cycle test temp head</td><td align="right">61&deg; C</td><td align="right">0%</td><td align="right">-10.3%</td><td align="right">111.5%</td></tr> <tr><td>3 cut test temp muffler</td><td align="right">143&deg; C</td><td align="right">0%</td><td align="right">-21.9%</td><td align="right">128.0%</td></tr> <tr><td>3 cut test temp head</td><td align="right">83&deg; C</td><td align="right">-2.4%</td><td align="right">-21.0%</td><td align="right">126.5%</td></tr> <tr><td>3 cut test time</td><td align="right">6.7 sec</td><td align="right">-2.9%</td><td align="right">-21.2%</td><td align="right">126.9%</td></tr> </table></center>