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Jim:<br>
Next time, could you be a little more detailed about what you're
doing?<BG><br>
Great job of giving us an idea of what's happening on the engine.<br>
A couple of years ago, Dick Hanson was doing a lot of work with the ZDZ
40 Side Exhaust. He had a lot of figures on performance, etc. that
would possibly be relevant to the work you're doing now. He was very
enthusiastic about the engine. Gerry Dale also did a lot of work on
putting a gasser in a pattern plane of his own design; you possibly saw
the article in RCM a couple of years ago; the airplane was called
"L'Essence" (not sure about the French spelling) but I've seen him fly
it in Masters and it did all the maneuvers. It was marginal as far as
weight went, and was sitting right at 11 lbs, Gerry said.<br>
<br>
Bill Glaze<br>
<br>
<a class="moz-txt-link-abbreviated" href="mailto:Jim_Woodward@beaerospace.com">Jim_Woodward@beaerospace.com</a> wrote:<br>
<blockquote
cite="midOF06F96C23.689CC613-ON85256F5B.0049F80E-85256F5B.004C6DE3@BEAEROSPACE.COM"
type="cite"><br>
<font face="sans-serif" size="2">Hi All,</font>
<br>
<br>
<font face="sans-serif" size="2">Here is an update to the ZDZ 40 RE
bench running. Since first post, I received a number of private emails
expressing some interest and excitement in the topic. Setup: ZDZ 40
RE (purchased Nov 04, Falcon ignition, Walbro carb), Webra MACS header,
Mintor 140 AL pipe, 93 Octane with Lawn-Boy Ashless oil mixed 32:1 per
instructions. The only modifications I've made thus far have been to
add a longer throttle arm to the carb. </font>
<br>
<br>
<font face="sans-serif" size="2">After running 60 plus oz of fuel
through the engine, you can imagine I've played with the needles a
little bit. Every 1/4 tank or so I noticed small changes in the sound
of transition, idle, or top end, so I would correspondingly change one
of the needles slightly. The trend of the motor was that the more the
motor broke-in, the richer it seemed to run. Small changes on the
needles are quite effective. What I found was that if you have the
idle screw too lean, the engine will run fantastic (perfect), but the
engine will take 30 flips to start when cold. If you have the idle
screw in the right location, cold starts (including priming), 10-15
flip range. On the bench, flipping with choke on and full throttle
(ignition off of course), is not practical as I've left the throttle
barrel return-to-idle-spring engaged for bench safety. Utilizing full
throttle, choke on, while priming is a procedure I've be en told
quickens the starting of the engine. Again, have not tried as I do not
have a servo controlling the throttle on the bench. Even at
low-throttle, choke closed 5- flips, the rest is done at low-throttle,
choke open, ignition on, until running. Even without the most
advantageous bench starting procedure, the motor cold starts pretty
quick. Hot starts have been "first-flip" starts 98% of the time. I'm
happy about this as it was a concern of mine. I am looking though to
reduce the "cold" start time a bit. If you consider 2 seconds per
flip, I'm looking at cold starts in the 30 second range. </font>
<br>
<br>
<font face="sans-serif" size="2">Initial running through 50 ozs:
Idle was smooth, but high through about 50 oz. The one time my tach
worked, it read around 2500 rpms (dead batteries). I was beginning to
wonder if the throttle barrel did not allow enough "throw" to close the
barrel and reduce idle rpm. Right about the 60 oz mark, the idle
seemed to drop dramatically. I ran for a few minutes like this, then
stopped the motor. After a total heat sink to ambient temperature, I
started it again and the idle hit this low-idle mark again and has
since, which leads me to Note One:</font>
<br>
<br>
<font face="sans-serif" size="2">Note 1: Do not take motor off the
bench until ridiculously low idle is reached. You will know you've
reached this point, because the windmilling of the prop and small
mechanical noises of the engine make more sound (mild sound) than the
"popping" of the combustion cycle. </font>
<br>
<br>
<font face="sans-serif" size="2">Note 2: Don't worry too much about
the low-end needle. Leave at 1.5 turns (factory suggestion) until Note
one is reached. Once the idle drops, adjust it for cleaner running.
Mine, even barely ticking over, still has very little vibration. Feel
free to adjust the top-end needle slightly until you at least have
clean 2-cycle full throttle reached. At the 1.5 top-end needle
starting point, the top-end is VERY rich.</font>
<br>
<br>
<font face="sans-serif" size="2">Note 3: I've broken in this engine
with a 18x10 APC Imac prop. I've done so because the larger props have
not arrived and I was anxious to get it running. Thus, I'm not sure
what effect a larger prop would have done to the break-in procedure or
specifically the high/low idle point I've mentioned above. Given my
current information, I don't feel mounting this to a plane for first
flip is a good idea. Put it on a bench, get to know the starting
procedure, etc. However, with the smaller prop, the engine does seem
to really sing with rpm. So, I have no doubt that this particular
engine is not rpm limited or such. I can hardly wait to get the larger
props on it. I was resistant to bench running, but alas, it was great
advice and I'm glad I took it. </font>
<br>
<br>
<font face="sans-serif" size="2">I also called two folks who monitor
the list to 'listen' to the engine while it was running, just for fun.</font>
<br>
<br>
<font face="sans-serif" size="2">Enjoy the hobby,</font>
<br>
<font face="sans-serif" size="2">Jim W.<br>
<br>
</font>
</blockquote>
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