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<DIV><FONT face=Arial>Vince</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Glow ignition has the advantage of light weight and
simplicity, but a disadvantage in that the ignition point can't be precisely
controlled. Spark ignition is essentially the opposite. Glow ignition made
powered model aviation practical for the masses by its simplicity, and later the
lack of RFI for RC. Of course, advancement in SI systems and materials now
minimize the RFI & weight penalties which have rendered these systems
commonplace for gasoline fueled 2-stroke cycle model engines.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>So - what is accomplished by converting a glow engine to
SI? The accurate control of ignition can reduce the chance of knock which drives
heat input upwards - removing this excess heat is one of the reason
for the high oil content of glow fuel - so less oil should be needed in the
fuel. (Gasoline fueled SI engines need very little oil for lubrication.) We also
tend to run glow engines on the rich side of optimum power A/F to prevent
detonation (knock) - so ideal control of ignition should allow leaner operation
and better fuel economy. Certainly a better idle is attainable through reliable
ignition events at low speed. OTOH - the ignition system is required to convert
low voltage to really high voltage (rapidly) and this comes a the price of
weight, both for the system (which requires a coil / transformer, RF shielding -
even with a capacitor discharge {CDI} that YS appears to be using) and a power
source. It's not certain if the benefits of a simple conversion offset the
weight penalty at this point.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>However - there are additional avenues available with SI.
Glow engines have a relatively low compression ratio, both to accommodate
various fuel mixtures (% nitro) and minimize knock. Increasing the C/R is an
efficient way to increase power - I toyed with this in the YS-AC days (still
have the ignition system) but the weight penalty was too great at that time as
both the ignition system and NiCads for power were heavy. Increased C/R
requires exact control of ignition - ideally with a feedback system to tailor
spark timing to real time operation (most cars have this). Spark timing
requirements vary with speed and load (less important for model engines), so
some system sophistication is desirable to accommodate these needs.
</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Compliments to YS for their development work. As usual -
they're innovative in developing a relatively simple system compatible with
current engines. I expect future YS use of SI will include both more engine
optimization and SI system sophistication. So - I've generally considered a YS
DZ akin to a Fuel Dragster engine with a ignition system handicap - looks like
the handicap is going away and there'll be a methanol / nitro burning
supercharged 4-stoke cycle model engine with accurate spark control (and it'll
last a lot longer than the dragster engine). Kudos to YS.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Times are good in pattern with developers and marketers of
engines, motors, fuels, and batteries providing us with options to power our
airplanes that best suites our needs and desires. Sure beats wound up rubber
bands!</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Earl </FONT></DIV>
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<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=vicenterc@comcast.net
href="mailto:vicenterc@comcast.net">vicenterc@comcast.net</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA NSRCA</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, May 16, 2008 6:09 AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [NSRCA-discussion] YS 160 - 170
Conversion to CDI</DIV>
<DIV><BR></DIV>
<DIV>Any comments on this conversion. Sounds very interesting.</DIV>
<DIV> </DIV>
<DIV><A
href="http://www.rcuniverse.com/forum/m_7498725/anchors_7502394/mpage_1/key_/anchor/tm.htm#7502394">http://www.rcuniverse.com/forum/m_7498725/anchors_7502394/mpage_1/key_/anchor/tm.htm#7502394</A></DIV>
<DIV> </DIV>
<DIV class=signature id=signature>--<BR>Vicente "Vince" Bortone</DIV>
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