Steve;
You are to be commended for some very scholarly work, and
excellent reporting. There are many hours invested there, as well as
expenses for equipment.
For nearly 2 years now I have been puzzled by my
observation of spark conditions during cranking that are consistent with your
findings. Since my engine has always started, and run well, I didn't have
motivation to pursue the causes. It may also be at least part of the explanation
for the inability to get smooth operation below 1200 rpm.
Of course my EC2 has been updated since, so I don’t
know if the behavior is still the same.
Coincidentally, just this past week I have done some
further tests of timing adjustment. You my recall from my dyno report
that the timing of my engine as I received it was way off because of the use of
a 12A front cover (and pointer) on the 20B engine. We set the CAS position based on estimated TDC
by observing the tip seals between the leading and trailing plug holes. During
the testing we verified the timing based on a trace from a pressure transducer
in a trailing plug hole; and decided that about -2 steps on the EC2 it 'looked
right'. I've been running that way since (and the 2 steps retarded may
have been a plus as far as starting spark is concerned).
Some time back I had varied the timing a couple of steps
during static runup; and could not discern a difference, so I left it as is.
I haven’t bothered with in-flight variation, partly because I was a bit
hesitant to be changing it during flight. I finally did so at lean cruise
conditions, and found that about 3 more steps retarding made a discernable
increase in rpm (5450 to 5500). So my EC2 is now set at -10 degrees from
default. I haven’t yet made any further spark checks, or even
observed if low idle is any smoother.
I may retard a bit on the CAS, and then do some more
observation to see if there is an ‘optimum’. Then set one of
the controllers 5 steps retarded for use in starting.
I guess you have now added to Tracy’s TTD list to figure out
what, if anything, should be done as a result.
Al
-----Original
Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf
Of sboese
Sent: Wednesday, December 09, 2009 2:30 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] EC2 signals
Steve,
Al and others who may be interested in EC2 ignition characteristics,
I
have added a page to the http://www.rotarycopilot.com/ website which is an
attempt
to show why I choose to use a 10 degree retarded mode 8 ignition
timing
setting. This setting is beneficial for startup and very slow idle
with
my EC2's.
The
previously mentioned download to this information has been removed from
the
website's downloads page. Now the information can be viewed directly
without
having to download, unzip, and open the html file.
With
the version of Internet Explorer I have, it is possible to click on an
image
from the web site page and download the original if a clearer image is
desired.
Steve
Boese
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