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<DIV><FONT face=Arial size=2>A lot of good points and discussion being made in
this thread - and nice to see no "feuding" amongst brands. It truly is
nice that options are out there.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>A couple more items to consider -</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Initial price vs. secondary costs -</FONT></DIV>
<DIV><FONT face=Arial size=2>- fuel - the average 2C is running on lower nitro
than the average 4C (do the math based on the number of times you fly in a
year).</FONT></DIV>
<DIV><FONT face=Arial size=2>- vibration - the average 4C vibrates more than the
average 2C (makes your own estimates for airplane longevity, servo gears, servo
pots, etc - and don't forget to include your time for completing the
maintenance).</FONT></DIV>
<DIV><FONT face=Arial size=2>- maintenance cost of engine - parts is
parts, they all wear, and all cost money to replace/fix. 4Cs have more
parts. Again, based on the number of flights you fly in a year, add up the
cost for parts and the time to make the repairs.</FONT></DIV>
<DIV><FONT face=Arial size=2>- Use the number of posts on this list as resource
to gauge what engines need more repairs.</FONT></DIV>
<DIV><FONT face=Arial size=2>- when I do the math, the 2C wins.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Throttle linearity and consistency -</FONT></DIV>
<DIV><FONT face=Arial size=2>- In my opinion, throttle linearity is far
over-rated - everyone has there own idea on what a linear throttle is - is 50%
stick = 50% RPM and 90% stick = 90% RPM? Linear to one person is not
linear to another - which is why you see many identical setups using different
throttle curves in the hands of different pilots.</FONT></DIV>
<DIV><FONT face=Arial size=2>- Throttle consistency is what we really care about
- if the throttle is consistent and predictable, it is easy to fly - and if it
doesn't feel linear, the "curve" can be adjusted to make it feel "more linear" -
the curve can be adjusted mechanically or with the radio.</FONT></DIV>
<DIV><FONT face=Arial size=2>- The other thing we care about is that the
throttle is symmetrical and without hysteresis - meaning throttling up to 50%
stick will get you the same RPM as throttling down to 50%. The biggest
instigator of hysteresis is a poorly setup piped 2C (but other things on both
2Cs and 4Cs can and do cause hysteresis).</FONT></DIV>
<DIV><FONT face=Arial size=2>- I've not had a problem getting 2Cs or 4Cs to run
consistently, so for me, this is a wash.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Influence of exhaust system on engine</FONT></DIV>
<DIV><FONT face=Arial size=2>- We all know the exhaust system is primarily to
quiet the engine, and secondarily to not detract from the power the engine makes
(or maybe increase the power the engine makes).</FONT></DIV>
<DIV><FONT face=Arial size=2>- How the exhaust system effects a 2C is very
different than a 4C - primarily because a 4C has dedicated intake and exhaust
phases, while a 2C shares them (gross simplification). Keeping things
simple, in a 4C, the best the exhaust system can do is scavenge the exhaust
gases from the combustion chamber and efficiently exhaust them out the
tailpipe, and depending on the design of the exhaust system, the torque curve
might be enhanced in some RPM ranges to a small extent. In a 2C, the
exhaust system can have a far greater influence on how the engine runs - it can
not only scavenge exhaust gases, but it can increase the volume/density of the
intake charge, AND it can affect the pressure (or vacuum) at the carb
itself. And with the 2C, the specific design of the exhaust system can
have a huge effect on the torque curve, peak power, and "linearity" of the
throttle.</FONT></DIV>
<DIV><FONT face=Arial size=2>- If you understand the above, you will also
understand that 2Cs do not suffer from lack of midrange torque and do not suffer
from poor throttle response - a poorly setup 2C may lack midrange torque and
throttle response, but so will a poorly setup 4C.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>If you think your engine has a linear throttle AND
consistent throttle, and you aren't using a throttle curve, an EFI, or an MC
carb (or the OS equivalent carb), then you don't need a throttle curve, an EFI,
or an MC carb (or the OS equivalent carb). If you don't think digital
servos work better than analog, you don't need digital servos either.
Point being, people (myself included) often don't realize the flaws in a current
system until they try a "better" one - nothing more than adaptive human nature
at work.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Many of the 2Cs available today and in recent years
have been labeled as poorly carbureted - because the carb appeared to
have rich/lean spots, flat spots, hesitations, etc. The majority of
the time, it is not the carb that has the problem - it is the fault of a poorly
setup or designed exhaust system (or one that is designed for max power, not
throttle response). Because it is possible for the exhaust system to
influence the pressure (vacuum) at the carb inlet, it can also affect mixture at
the carb. So, if your 2C carb has rich/lean spots, there are 2 ways to fix
it - re-tune the exhaust system, OR, adjust the carb mixture at that throttle
setting. Fixing with the exhaust system is where the whole art of 2C
tuning comes into play - Odds are, if you copy the setup (prop, plug, fuel,
pipe, tune length, header) recommended by the manufacturer, you won't have any
carb issues - the manufacturer has already done the 2C tuning so you don't have
too.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>At this point, I haven't been brand
specific.........</FONT></DIV>
<DIV><FONT face=Arial size=2>- The most linear consistent throttling engine I
have ever run was a prototype KB150 using a Bolly 590 muffler - 20% nitro and NO
PUMP - just muffler pressure (yes, I did have to change the jetting in the carb
several times to get it perfect, but the production version wouldn't need that
tweaking). A shame the engine never made production.</FONT></DIV>
<DIV><FONT face=Arial size=2>- I've run and seen countless examples of
Bully145s, Webra145s, OS140RXs, OS160FXs, OS140/160 EFIs, Mintor 140/170s, and
most of the YS 4Cs that all had very consistent throttle response using a
variety of exhaust systems and fuel.</FONT></DIV>
<DIV><FONT face=Arial size=2>- I've also run and seen all of the above engines
running poorly with a poorly setup exhaust system.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Why use an EFI? Why use an MC? Because
it allows the carburetion to be matched to a greater variety of exhaust setups -
and it does increase the linearity and consistency compared to the majority of
setups being used (but you might not believe it until you try it, and maybe the
amount of difference won't convince you to change). The OS EFI system
allows the mixture to be set at 3 points - idle, midrange, and high speed - and
then it self regulates the mixture (to an extent, only effectively within a
limited regime). The MC (and OS equivalent carb) allows the setup to be
adjusted just about anywhere (8 points is easy with a JR 10X, I can't speak for
other TXs, but figure they are close to the same). And as has been pointed
out, both systems have some advantages so far as no needle valves.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>A 140 EFI is $1,000.00 and while the mechanicals
are very durable (with the SS rear bearing), the injectors can be a
problem.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>A 160 MC is under $500 and should be very
durable (based on the track record of the Webra145s).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Regards,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Dave Lockhart</FONT></DIV>
<DIV><FONT face=Arial size=2><A
href="mailto:DaveL322@comcast.net">DaveL322@comcast.net</A></FONT></DIV></DIV></BODY></HTML>