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<DIV>Steve,</DIV>
<DIV> </DIV>
<DIV>Agree with you 100% - well, with one exception <G>.</DIV>
<DIV> </DIV>
<DIV>On a 2C, all exhaust systems are tuned to some extent in some RPM range -
the good mufflers have so little tuning that it is not noticeable. I've
had very good success with the Bolly 590R on several 2Cs. The power
difference is substantial - to the point that I would say a muffled 2C is
slightly down on power compared to a 140 DZ on 30%. Personally, I'd still
take the muffled 2C. <G>.</DIV>
<DIV><BR>Dave</DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=Patternrules@aol.com
href="mailto:Patternrules@aol.com">Patternrules@aol.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, January 22, 2004 6:34
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: 2Cs - Misc</DIV>
<DIV><BR></DIV>
<DIV>
<DIV><STRONG> Dave a very good write up but I believe you missed one
point, the way Jeff Hughes and me have been doing it, Muffler instead of pipe,
no tuning, no midrange problems, no Idle problems, no EFI, no MC Carb,
</STRONG><STRONG>A little less peak RPM but plenty of power and for sure the
simplest to setup. Extremely reliable and probably the best for anyone new to
this sport.</STRONG></DIV>
<DIV><STRONG> Steve Maxwell</STRONG></DIV>
<DIV>In a message dated 1/22/2004 2:36:45 PM US Eastern Standard Time,
DaveL322@comcast.net writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid">
<DIV><FONT face=Arial size=2>To add to several of the recent posts RE 2Cs,
some misc thoughts/data from my experiences.</FONT></DIV>
<DIV><FONT size=2></FONT><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial size=2>The question has been asked, how much power is
enough/needed - how much more is needed? If you have enough power, and
it is consistent, quiet, friendly, smooth, reliable, cheap, etc - you don't
need more. However, having too much power (haven't found it yet
myself) allows several things - milder cams, smaller carbs, lower
compression, richer needle setting, lower nitro, milder porting, milder
tuned exhaust systems, etc - all of which are essentially
trading "extra" power for something else that is nice to have - ie,
cheaper, quieter, consistency, more linear response, more torque,
etc.</FONT></DIV>
<DIV><FONT size=2></FONT><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial size=2>With 2Cs, I've posted before how the exhaust
system can have a huge influence on not only the peak power of the engine,
but also on the midrange running characteristics. Tuning the exhaust
for peak power usually has some nasty side effects - non-linear throttle and
rich/lean spots in the mid-range being the biggest nasties. The old
"traditional approach" to mitigate the nasties was to test many
combinations of props, plugs, compression, nitro, oil, pipe lengths, pipe
designs, and port timing on the engine itself. The point in time when
the "average" pattern flier probably knew the most about the "traditional
approach" was probably in the mid to late 1980s - piped 2C 60s were
propped between 13,000 to 16,000 RPM on the ground (10-11.5" diameters and
7-9" pitches), and the tune length of the pipe (diverging/converging cone
type, mufflers were rarely used) was 13-15" (plug to baffle).
After the introduction of turnaround and noise limits, and just prior to the
4Cs becoming dominant, 10,000-12,000 RPM (11-13" diameters, 9-12" pitches)
and 17-20" (diverging/converging cone type, and baffle type, still no
mufflers) were the norm for 2Cs. A couple 2C guys on the fringe
were running even bigger props, with longer pipes, and lower RPM. My
personal setup at that point (1992) was a Webra Race 61 LS w/ Dynamix using
a CF pipe set at 22" and turning an APC 13-13N at about 9,500 - not a
friendly setup - few aside from myself could set the needle, but
the power was awesome, and whisper quiet.</FONT></DIV>
<DIV><FONT size=2></FONT><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial size=2>Today, the "traditional" approach to tuning a
2C still works, AND, some new approaches exist - the OS EFI system and the
MC carb system. The "traditional" approach today includes tuning the
engine not only for peak power, but for peak power at a lower RPM and
with linear throttle response as well - and relative to the mid/late
1980s, the average pattern flier knows substantially less about 2C
tuning. All three systems will yield the same amount of peak
power - EFI and MC do not yield more top end power. However, when the
goal is peak power AND a smooth midrange - it is easier to achieve that goal
using EFI or MC - the "traditional" approach requires substantial 2C
knowledge and/or experimentation. Very often the "traditional"
approach sacrifices a little bit of peak power to get the smooth midrange
(and retain some flexibility/consistency) and it is for that reason that the
average EFI or MC setup produces a tiny bit more power than the std carb
(traditional setup). The "best" 2C setup, IMHO, is going to be one
that is "traditionally" setup with the addition of EFI or MC, to allow very
fine tuning and more consistency and flexibility (with regards to changing
weather, props, fuel, etc). A very poorly setup 2C is not going to
become wonderful with the addition of EFI or MC.</FONT></DIV>
<DIV><FONT size=2></FONT><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial size=2>Aside - in my experience from running the OS140
EFIs and 140 RX - the EFI system has a "sweet" spot - it wants to be propped
between about 7,700 and 8,300 RPM on the ground which will yield about 8,300
to 9,000 RPM in the air - if the 140 EFI is setup outside of that range, the
power drops substantially. OTOH, an OS140RX can be tuned to run
extremely well from 7,400 up to 8,800. I've not found a 2 plug head to
provide more power or a lower idle - but the needle setting becomes less
critical. And while Shadel piston/sleeve is a great weight saver
(40 grams), I've not found it to produce any more power. And if
the engine ever gets hot on the ground, the stock setup (ringed) idles a
little better (never noticed a difference in the air tho).</FONT></DIV>
<DIV><FONT size=2></FONT><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial size=2>Regards,</FONT></DIV>
<DIV><FONT size=2></FONT><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial size=2>Dave Lockhart</FONT></DIV></BLOCKQUOTE></DIV>
<DIV><STRONG></STRONG></DIV>
<DIV> </DIV>
<DIV> </DIV>
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