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