[NSRCA-discussion] First day out with OS 140RX (somewhat long)

[Rcmaster199 at aol.com]

NOPE, you're not gonna get me!! I don't do longwinded stuff, not even my  
own. This might be first chapter of your Thesis tho. (BG)
 
Matt
 
In a message dated 3/1/2006 7:39:43 PM Eastern Standard Time,  
dflynt at verizon.net writes:

Today  was one of those beautiful California days, in between the rain, and I
have  the week off, so I finally got my ZNline Supreme in the air for  several
trim flights.  Also, I switched from the Webra 160 with M/C to  the OS 140RX.
Below are my initial impression of OS, along with comparison  to YS 140DZ:

I was particularly careful while breaking in the OS.   I wanted to ensure no
problems, and the engine was ready for fly  time.  I broke in on the bench
with one gallon of fuel.  I saw  7800 rpm with a 16.5x12w prop mounted in the
plane today, fairly  rich.  I'm hoping I have it set way too rich, and that
it will gain  more power as I get more fuel through it.  My setup is a Karl
Mueller  header at 9 3/8 inches from from exhaust flange to the entrance of
the  pipe, and an ES 2C140M80 muffler.  Cool Power 15%.  The Mueller  header
has a sharper rise over the OS or Hatori header, and I needed that  to clear
my firewall.  Total length due to the sharper rise is near  the same as the
stock OS header.  What a nice header BTW.  It has  the right thrust built in
so it is straight down the middle of the pipe  tunnel.  It came with a short
extension so that there is stress relief  on the header to prevent it from
breaking.

Big two strokes are new  to me.  Before this engine, I was running a YS
140DZ, and before that,  YS 120 - 140.  Here are my initial observations and
comparison between  the 140DZ and 140RX:

Ease of use:  Probably a toss up.  The  OS is very user friendly, and is
simple, and runs on sport fuel.  It  is not as easy as the YS in that you
need to tune header length and select  optimal prop and muffler/pipe, however
for the OS you can stand on somebody  else's shoulders, and that is what I
did for the most part.  I don't  know if I am done tuning it however.  Both
engines are pretty much  hands off once broken in and set (at least what I
hear for the OS).  I  flew 300 times with the DZ, and never touched the
settings after break  in.

Ease of start:  Hands down, OS.  This engine starts with  ease.  The DZ, once
you learn it, will start easy so long as you have  a strong starter and
strong glow source.  But it can lock up on you if  you allow it to flood.

Idle:  Definately the OS.  I had a  good idle after one gallon, and I still
have not touched the low end from  factory setting.  The YS will idle ok for
a while once warmed up, but  it won't idle forever.  It does not really
matter so long as you do  not let it idle for long periods.

Reliability:  No way to know  since I don't have time on the OS, but one
strike against it today.   It flamed out at the bottom of the reverse
avalanche.  I just made it  back, heart pounding all the way.  This is
probably an anomaly, and I  only have 1 1/2 gallons through it (I should not
have been practicing the  reverse av with such little time on the engine, but
oh well).  Idle  speed was 2000 on the ground.  On the first flight however,
I overshot  the runway twice, and I had to go around.  So, it stayed lit when
it  counted.  The DZ never flamed out during flight.  I speculate that  the DZ
is more reliable, but I am splitting hairs.

Quietness in the  air:  OS is quieter, like a whisper compared to the DZ.  DZ
has a  lower pitched noise.

Vibration:  OS is much less vibration and  very smooth at idle through full
thottle.  There is an area about 1/4  throttle where it shakes a little, but
not bad compared to the DZ.   The 160DZ I hear is a lot smooother than the
140DZ, which would be  nice.

Torque:  Hands down, the DZ.  The DZ has a smooth,  linear throttle curve and
usable torque at any throttle setting.  This  is what is so great about the
DZ.  The OS is fairly limp and useless  until you get past 1/3 throttle.  At
half throttle it comes alive, and  at 5/8 throttle to full throttle, there is
little difference in  output.  I think this is one of the major differences
between two  cycle and four.

Power:  The OS does ok, but the DZ is far more  powerful.  Maybe I need more
time on the OS before a fair  comparison.  I have a gut feeling however, from
running this and  watching other OS owners over the years, that the DZ
dominates in  power.

Weight:  OS with ES muffler is probably 3-4 ounces lighter  than a DZ with
similar muffler.  But I think the DZ might be  equivalent weight with a
Hatori short pipe.  Not sure.

Fuel  requirements:  DZ runs best on one type and brand of fuel:  Cool  power
30% heli.  This is expensive stuff, and is my major gripe with  the DZ.  The
OS ran outstanding with 15% sport fuel.  For  economy, you cannot beat this.

Smoke trail:  DZ has a thick smoke  trail with CP 30%.  This OS had fair
amount of smoke, but I expect it  to decrease as I lean in.  None of OS' that
I see at contests have a  heavy smoke trail.

Overall preference:  This is a little tough  because the DZ performs better
for pattern, but the OS is probably good  enough.  Greg Frohreich flies very
well with his OS, and until I can  fly better, I wonder if I need a better
engine.  Still, the DZ is a  pleasure to run, with exception of the expensive
fuel.  I choose the  DZ as my preference, but I like the OS for the positive
characteristics I  mentioned.


David





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