Steve,
As I have been
accumulating time on my installation, I have been trying to improve on my
tuning of the fuel system also. The system could never be tuned to be
stable at any mixture setting except quite rich at any manifold
pressure. I recently reached the conclusion that maybe my primary
injectors were not working properly which was confirmed by removing them and
flow testing them. These injectors had over 100,000 miles on them
in the car if they hadn’t been replaced somewhere along the way. The
original secondary injectors appeared to work fine. I obtained 2 new
injectors from RC engineering and installed them in the primary positions with
the original secondary injectors in the secondary locations. The new
ones are saturated disc type injectors of 440cc flow rating as opposed to the
peak and hold pintle type originals of 460 cc flow rating. The engine
could be tuned much better at higher manifold pressures but still did not idle
well, in fact the idle was much worse. The original secondary injectors
were then installed in the primary locations and the new non stock injectors
were installed in the secondary locations. Idle was now much better at
2000 rpm but still is a little rough below this to 1500 rpm which is as low as
was tried. Tuning at higher manifold pressures is still effective with
this configuration.
While tuning the
system on the ground this last weekend, I recorded the pulse widths of the
activating pulses of the primary injectors under conditions of idle to full
throttle. Pulse widths of as low as 1 millisecond were observed at idle
and just above the staging manifold pressure while pulse widths of up to
slightly over 3 milliseconds were observed just below the staging point and at
full throttle. The supplier of the new injectors said that those
injectors were not expected to operate reliably at pulse widths less than
about 1.5 milliseconds which was also observed on the injector test
stand. The original secondary injectors worked down to about 1.2
milliseconds under the same test conditions. The driver in the EC2
must be able to operate the injectors at lower pulse widths than the test
stand since pulse widths less than 1.2 were observed in the plane with the
engine running quite well. It is my observation that in my case at
least, the injectors may be operated at the lower limit of their useful range
at idle and improvements to idle quality may be difficult. Rich settings
may be required to get the injectors working reliably at
idle.
Please note that
these are only my observations and in spite of the colder weather here in
Wyoming, I have not seen density altitudes of less than 7000 feet yet so what
I see may not have much bearing on what is observed in the real world.
Also I may just be hallucinating due to oxygen deprivation. Tracy, of
course, would be the one to consult for the best
information.
For what it is
worth…
Steve
Boese
34 uneventful hours
on RV6A, 13B NA, EC2, RD1A
-----Original
Message-----
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Steve Brooks
Sent: Tuesday, December 12, 2006 6:56
AM
To: Rotary motors in
aircraft
Subject: [FlyRotary]
Re: Great Flight
Tracey,
You are
correct. Messing with mode 3 in the air is not a good idea. Also
when it running good, not messing with it, is also a good idea.
I guess that I just
had too much time on my hands on the 190 NM trip, and had to see if I could
make it better. I’ve added that to my list of things NOT to
do.
As far as working
with a turbo, the last update that I got about 10 months ago works very well,
and factory default tuning isn’t too far off. I have to give it about 4
clicks on mode 3 toward lean to get it in at 23 MAP and 12 o’clock
mixture. Lean it a little at lower power levels, and go richer at higher
power levels.
The only thing I
haven’t figured out is how to get it to really idle well. I have to run
it rich to run fairly good, but it seems to run a little rough. Leaning
at idle makes it runs really well, just before it
dies.
Steve
Brooks