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<DIV><FONT face=Arial size=2><SPAN
class=500465810-18092002>Matt,</SPAN></FONT></DIV>
<DIV><FONT size=+0><FONT face=Arial><FONT size=2><SPAN
class=500465810-18092002>Your point:"</SPAN>The idea is to get uninterrupted air
flow in the throat of the venturi, by moving the spray-bar against the wall of
the venturi. Better breathing results in more power for a given set of
parameters.<SPAN class=500465810-18092002>" is a very good one, and I think
"</SPAN>uninterrupted<SPAN class=500465810-18092002>"
deserves several additional comments, especially for those who have
not seen a slide valve function.</SPAN> </FONT></FONT></FONT></DIV>
<DIV><FONT size=+0><FONT face=Arial><FONT size=2><SPAN
class=500465810-18092002>With the slide valve the air flow is straight
through the variable orifice to the spray bar. However, for the purpose of
comparison consider a</SPAN><SPAN class=500465810-18092002>ir flowing toward a
spray bar through a carb with openings in a rotating barrel inside a fixed
cylinder. The flow path of the air has somewhat of a 'Z' or 'S" shape.
This means two relatively gradual changes in direction of air flow occur at half
throttle and increasingly severe changes in direction happen as the idle
position is approached. This rapidly reduces the velocity and energy of the
stream of incoming air and it's ability to spray the fuel via high quality
external atomization from the spray bar. Quality of atomization decreases
at the critical idle position. Local air-to-ATOMIZED-FUEL-ratio (rich/lean
etc.) could bounce around in a non-linear fashion and reduce
combustion stability, heat release rates, and efficiency. This could cause
a richening-mixture effect on throttle up as atomization improved and efficiency
increased. Also it could promote unwanted combustion quenching (chilling) at or
near idle. </SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT size=+0><FONT face=Arial><FONT size=2><SPAN
class=500465810-18092002></SPAN></FONT></FONT></FONT> </DIV>
<DIV><FONT size=+0><FONT face=Arial><FONT size=2><SPAN
class=500465810-18092002>I feel that a slide valve carb retrofit in
combination with dual plugs could give very serious top and
carefree performance without significantly-increased weight, electronic
complexity, or small diameter fuel injection ports. The Webra slide valve was
not at all sensitive to fuel properties over my one-year period of heavy
use back then with fun fly contests almost every weekend in the
</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT size=+0><FONT face=Arial><FONT size=2><SPAN
class=500465810-18092002>Ohio, Pennsylvania, and West Virginia circuit. Zero
problems of any kind. My total engine back up on the road consisted of a spare
prop nut and some wooden props. At that time I paid $100 for the new engine.
</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT size=+0><FONT face=Arial><FONT size=2><SPAN
class=500465810-18092002></SPAN></FONT></FONT></FONT> </DIV>
<DIV><SPAN class=500465810-18092002><FONT face=Arial
size=2>Chuck</FONT></SPAN></DIV>
<BLOCKQUOTE>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> discussion-request@nsrca.org
[mailto:discussion-request@nsrca.org]<B>On Behalf Of
</B>Rcmaster199@aol.com<BR><B>Sent:</B> Tuesday, September 17, 2002 10:11
PM<BR><B>To:</B> discussion@nsrca.org<BR><B>Subject:</B> Re: OS 140 RX with
Dual Plug Conversion plus Webra Memories <BR><BR></FONT></DIV><FONT
face=arial,helvetica><FONT lang=0 face=Arial size=2 FAMILY="SANSSERIF">In a
message dated 9/17/2002 12:44:23 PM Eastern Daylight Time,
chuckwagon@charter.net writes:<BR><BR><BR>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid; MARGIN-RIGHT: 0px"
TYPE="CITE">Subj:<B>OS 140 RX with Dual Plug Conversion plus Webra
Memories </B><BR>Date:9/17/2002 12:44:23 PM Eastern Daylight
Time<BR>From:<A
href="mailto:chuckwagon@charter.net">chuckwagon@charter.net</A><BR>Reply-to:<A
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A><BR>To:<A
href="mailto:pattern@rcmailinglists.com">pattern@rcmailinglists.com</A>, <A
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A><BR>CC:<A
href="mailto:lee@piedmontmodels.com">lee@piedmontmodels.com</A><BR>File:<B>winmail.dat</B>
(1784 bytes) DL Time (203344 bps): < 1 minute<BR><I>Sent from the
Internet </I><BR><BR><BR><BR>Dual
plugs<BR>anyone?http://www.rcaerosport.com/articles/reviews/evolis/crino/e10.htm
(I<BR>remember my very smooth running dual-plug Merco 60.)<BR><BR>Also
another 2-stroke memory... the great Webra slide valve carb. Mine<BR>seemed
to give INSTANT RPM up from an all-day idle with my stock single
plug<BR>Webra black head engine! It had almost zero spool-up or spool-down
time to<BR>or from any level(s) I chose. Blip...blip...blip <happy
smile>. Once I made<BR>an adaptor and tried the slide valve with a ST
blue head. Same dynamics.<BR>Also gave more HP than the stock ST carb. Just
some thoughts.<BR>Chuck </BLOCKQUOTE><BR><BR>Chuck <BR><BR>the Dynamix carb,
or slide valve carb, that you mention worked extremely well for me also. Duke
Fox first used the concept in model engines back in the sixties I believe. The
concept was not lost on Webra, since their Dynamix carb was a most effective
device.<BR><BR>The idea is to get uninterrupted air flow in the throat of the
venturi, by moving the spray-bar against the wall of the venturi. Better
breathing results in more power for a given set of parameters.<BR><BR>Matt
Kebabjian</FONT> </FONT></BLOCKQUOTE></BODY></HTML>