Engines - long

[David Lockhart]

Warning - this email may offend both 4C and 2C fans.

In the late 80s, 2Cs dominated - almost exclusively because of the rules in
place at the time (no displacement advantage given to a 4C).  When the rules
changed to allow a 2:1 displacement advantage for the 4Cs (an error at the
time recognized only by a minority) in the interest of promoting engines
that were quiet (ironic, yes??), the 2Cs remained dominant until the
knowledge base of the majority of pilots shifted to the 4C camp after
several years of 4C development triggered by the 2:1 rules change.  The more
recent rule change allowing unlimited displacement makes the 2C once again
viable.  And for the past several years, the 2C power setup has been in
development - specifically in areas of throttle response and linearity.
Outside of specific developments driven by rules, I offer the following
generalizations -

- For a given weight, 2Cs make more power.
- For a given amount of vibration, 2Cs make more power.
- Among the current crop of engine choices for pattern, 2Cs consume less
fuel, and cost per gallon is less.
- Among the current crop of engines/exhaust systems, the 2Cs are quieter.
- The 4C naturally has a relatively linear throttle with a relatively broad
torque curve, the 2C requires some pretty specific exhaust (or carb) tuning
to achieve an equally linear throttle and broad torque curve.
- 4Cs have a relatively smaller, lighter exhaust system, which partially
offsets the heavier weight of the engine, but is also more prone to header
breakage and coupler meltdowns (vibration and heat).

I ran YS4Cs way back - the SF and AC, and am quite happy to have never owned
anything in the series beyond the AC - they caused me enough grief.  I've
seen countless numbers of the YS4Cs over the years and when running
correctly, they are wonderfully engineered/designed powerplants - however,
I'm in agreement with Ed Miller regarding what it takes to get a YS4Cs to
really run good and last.  I've only seen a handful of YS4Cs that ran well
out of the box and experienced any longevity.  I've seen a greater number
that wouldn't run due to QA/QC issues.  The vast majority of good YS4Cs I've
seen were hand assembled and fit by guys like Ed Miller, Mike McCormick,
Rusty Fried, Rick Mattie, and Rich Verano.  I find it quite ironic that a
few of the YS4C faithful claim that every YS they've owned ran great from
day 1 with no mods, but yet the same few know of countless modifications and
repair tricks to get the bad YS4C running - seems to me this knowledge could
only be gained by experiencing the problems.  And if you are lucky enough to
have a good running YS4C, it still vibrates and beats the crap out of the
airframe and servos, costs a fortune in fuel, and makes more noise.  Oh, and
on the noise topic - if the peak power of a 4C is only equal to a 2C when
the 4C is exceeding the noise limit and the 2C is not, the power isn't equal
is it?  The biggest appeal (and only appeal) to me about the YS4C is that
very little tuning is needed to have the relatively linear midrange and
torque - so long as it is run at relatively high RPM on high nitro.

On the 2C side, I've run a variety of KB, OS, and Bully/Webra engines and
found that all made/make more than enough power to handle 11lbs through FAI
sequences with ease on 15-20% nitro, and at 91+/- dB.  With careful exhaust
tuning, the throttle was very linear and consistent on the KB150 and 140RX
and the engines could be setup to run very nicely anywhere from 7300 to 8700
RPM.  The 140EFI is a little different - the throttle is smooth and linear
no matter what you do with the exhaust system, but for good power in the
air, it needs to be propped between about 7800 and 8300.  The Bully/Webra145
I could either setup for very good power, or very linear throttle and good
torque - but not both.  The KB/OS would go 200+/- flights on standard
bearings and the Bully/Webra 100+/-.  A stainless steel bearing in the OS
was good for at least 500+ flights.  Conrods and piston/ring/sleeves were
usually good for 400-500+ flights in all engines.  I've observed the Mintor
engines and they appear to be receptive to providing strong power, good
torque, and good throttle response.

I'm currently running Webra 160s w/ MC carbs and Perry remote pumps.  I've
not found the stock backplate pump to be consistent when mounted in the
backplate (heat issue) and only marginally more durable when mounted
remotely (and I understand this problem is being actively worked on by
Horizon and Webra).  The Perry thus far seems to be more consistent and
durable. Bearing life is 125+/- and should improve 3-4x with a full
stainless steel bearing (recently available from Boca).  I wore out a conrod
and piston/ring/sleeve quickly due to some heating problems associated with
a bad pump, but expect those parts will be good for 300+ flights with the
Perry pump in place.  The MC carb allows a variety of exhaust options to be
used and enables the throttle to be very linear - it is the most linear of
any model engine I've ever seen run - 2C or 4C.  The engine makes a ton of
torque and responds instantly in the air to any change in throttle.  I had
engine problems at the 2004 NATs, but believe they are largely resolved.  I
put up 6 flights at the D4 Champs this past weekend and I'd be willing to
bet that anyone who saw any of the flights would agree that my setup -
- was the quietest,
- had the best brakes,
- was the most constant speed,
- had plenty of power and speed, even in the rather strong crosswind.

My 160MC setup is 15% S+W fuel, Johnson header, Asano pipe, 15.75-11 3b,
approx 7500 at launch, in a 9.75 lb Vivat.  Full throttle is used very
little, and I can get 2 full P05 sequences on 16 oz of fuel and still have
1-2 oz in reserve.  I believe the setup is very constant in speed - and part
of that is due to the use of the 3b prop.  I've found the 3b to have better
braking, and be easier to fly constant speed (less throttle management
needed) - but it is a less efficient prop and requires more torque/power to
generate the needed thrust and speed.  It is a competitive advantage for
those that have the powerplant to spin the prop (2C or maybe a 160DZ, as
even when reduced to a 10" pitch, 140DZs on 30% nitro will not effectively
run the prop).  Some may recall Quique used a 15.5-12 4b on his 160DZ this
year - I wonder why??  Noise?  Braking?  Both?

I find the discussion regarding how many 2C/4C/electrics made the finals in
Masters/F3A at the NATs, EC, or Team Trials rather interesting.  Seems to me
anyone with minimal effort can ascertain that top level pilots have placed
well with all varieties of power plants.  With the recent specific
references to the 2004 NATs F3A, I recall -
- a YS sponsored pilot flying a 2C in his primary plane because the YS
wouldn't run, and then borrowing a YS when the YS in his backup failed.
- a pilot who used 3 separate engines to get through 10 competition flights.
- numerous backup engines "on loan" during the contest.
- at least 1 YS deadstick in the finals.
Am I too believe that all of the above were isolated problems and
miraculously coincident to the finals?

And while not positive, I believe every pilot in the 2004 NATs F3A finals
was sponsored by YS - and YS by far sponsors the most pilots.  I'd be
willing to bet that if OS, Webra, or Hacker provided an equal level of
sponsorship the number of sponsored YS pilots would diminish substantially.
In view of the engine problems I had at the 2004 NATs, I was asked by 2 of
the finalists why I was running the 2C and not a 4C.  I replied less weight,
less vibration, more power, more reliability - and while neither disagreed,
both felt having a YS sponsorship made the difference (as they both believed
I would be able to obtain YS sponsorship).

I'm sure some of the YS fans are crying blasphemy - and I bet the 2C fans
are grinning, and the 2C setups are only going to get better, until the
electric setups kill both the 2C and 4C.

Regards,

Dave Lockhart
DaveL322 at comcast.net

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