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

[Ed Alt]

Dave:
Re the flame out, could be lot's of things ofcourse, but if you are not 
already trying one, you may want to use a type F plug.

Good writeup of your experience!
Ed
----- Original Message ----- 
From: "David Flynt" <dflynt at verizon.net>
To: <nsrca-discussion at lists.nsrca.org>
Sent: Wednesday, March 01, 2006 7:40 PM
Subject: [NSRCA-discussion] First day out with OS 140RX (somewhat long)


> 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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