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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I believe that the stock silencer for the
120AX has quite a bit of back pressure. In my Venus I moved the fuel tank
to the most reward possible position and tried it w/o a pump. No difference in
performance from the forward position even on long verticals.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
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<p><b><i><font size=4 color=navy face="Brush Script MT"><span style='font-size:
13.5pt;font-family:"Brush Script MT";color:navy;font-weight:bold;font-style:
italic'>Jay </span></font></i></b><b><i><font size=4 color=navy
face="Brush Script MT"><span style='font-size:13.5pt;font-family:"Brush Script MT";
color:navy;font-weight:bold;font-style:italic'>Marshall</span></font></i></b><font
color=navy><span style='color:navy'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>-----Original Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> </span></font><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>nsrca-discussion-bounces@lists.nsrca.org</span></font><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> [mailto:</span></font><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>nsrca-discussion-bounces@lists.nsrca.org</span></font><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Bob Richards<br>
<b><span style='font-weight:bold'>Sent:</span></b> Saturday, October 06, 2007
9:22 PM<br>
<b><span style='font-weight:bold'>To:</span></b> </span></font><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>NSRCA Mailing
List</span></font><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma'><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [NSRCA-discussion] OS
120AX header?</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Jim,</span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>I have not run my 120AX enough to conclude anything
yet, but the little bit that I have run it left me thinking there was not
enough muffler pressure either. I tried with/without the internal baffle, but I
think the best combo would be to leave the internal baffle out and try
restricting the tailpipe as you say.</span></font></p>
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<div>
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style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>There are a couple of guys in our club that have the
120AX running the Jerry Smith mousse can mufflers and get MUCH better
performance, and more reliable running as well since there is considerably more
muffler pressure. They also fly several Outlaw delta planes with .32 size
engines and do incredible manuevers, using the same type muffler setup.
The only way they can pull the Gs they do and still run is because of the much
higher backpressure.</span></font></p>
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style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>With a large volume muffler (the larger the better)
the more pressure you can run in the muffler and the engine still run fine. In
fact, you will burn less fuel as well since less excess fuel/air mixture blown
out of the exhaust during the exhaust scavenging.</span></font></p>
</div>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>I did a lot of muffler/prop experimenting (sport
planes) many years ago. :-) I learned a LOT.</span></font></p>
</div>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Bob R.</span></font></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><br>
<b><i><span style='font-weight:bold;font-style:italic'>J N Hiller
<jnhiller@earthlink.net></span></i></b> wrote:</span></font></p>
</div>
<blockquote style='border:none;border-left:solid #1010FF 1.5pt;padding:0in 0in 0in 4.0pt;
margin-left:3.75pt;margin-top:5.0pt;margin-bottom:5.0pt'>
<div>
<p class=MsoNormal style='margin-left:.5in'><span class=EmailStyle20><font
size=2 color=navy face=Arial><span style='font-size:10.0pt'>16 x 10 should be
no problem. I have run one all season with stock muffler. I didn’t like
how many RPM’s the 16 x 8 turned in horizontal flight.</span></font></span></p>
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<div>
<p class=MsoNormal style='margin-left:.5in'><span class=EmailStyle20><font
size=2 color=navy face=Arial><span style='font-size:10.0pt'>This may be a
little off subject but may be of interest to other 120AX users.</span></font></span></p>
</div>
<div>
<p class=MsoNormal style='margin-left:.5in'><span class=EmailStyle20><font
size=2 color=navy face=Arial><span style='font-size:10.0pt'>I fought a rich
midrange (poor transition) from day one in order to keep from running too lean
on a long vertical pull, which seamed to get worse in cool air. I have two
motors that have different carburetors and focused on this as a problem even
though both acted similar eventually concluding that there wasn’t enough
muffler pressure. I have never gotten along well with pumps so I tried
restricting the muffler outlet using a short exhaust tube (3/8” ID) with
a brass tube insert. I tried a couple different sizes settling on 13/32 OD,
which is pinched on the end from cutting with a tubing cutter (.350” ID).
Flaring the other end keeps it in the exhaust tube without clamps. I also tried
an OS-“F” plug which I thing may be better than the #8. It will be
9 months before I can run it in hot weather but I was able to run leaner without
starving in the verticals and the transition is immediate.</span></font></span></p>
</div>
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<p class=MsoNormal style='margin-left:.5in'><span class=EmailStyle20><font
size=2 color=navy face=Arial><span style='font-size:10.0pt'>Jim Hiller</span></font></span></p>
</div>
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<p class=MsoNormal style='margin-left:.5in'><span class=EmailStyle20><font
size=2 color=navy face=Arial><span style='font-size:10.0pt'>Spokane</span></font></span></p>
</div>
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<p class=MsoNormal style='margin-left:.5in'><span class=EmailStyle20><font
size=2 color=navy face=Arial><span style='font-size:10.0pt'> </span></font></span></p>
</div>
</blockquote>
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style='font-size:12.0pt'> </span></font></p>
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