Further to my last posting on
the subject; we did the following changes to my 20B EC2
- reduced values of the added
caps for noise filtering on the ignitions circuits by a factor of
ten.
- replaced the MAP pressure
sensor on Controller “A”
- added what is being referred
to as the ‘clamping diodes’ or ‘snubbers’ on the injector
circuits.
Changing the capacitors had no
noticeable effect on what I believed was a timing issue. I still find
that at low power disabling leading coils has definitely more effect than
disabling trailing; whereas at high power, say about 19” MAP and above,
disabling the leading has small effect and disabling trialing has larger
effect. I have concluded that the timing is not late with both on; since
I found that now retarding the timing a 2-3 steps (4-5 degrees) at power
increased the rpm a bit. I think the larger caps did result in a small
retarding of the spark.
Does anyone else with a 3-rotor,
and using the LS1 coils, note the same
behavior when disabling leading/trailing ignition? Tracy
mentioned that on his 20B using the renesis coils, disabling either set
results in the engine stopping, so there may be something amiss in the
circuitry.
I thought that the strange
leaning of mixture with altitude when running on controller A was solved by
replacing the pressure sensor – until I got over 5000’. Then over the
next 200 ft increase the mixture monitor bar on the EM2 went slowly off the
bottom of the scale, and it took turning the mixture knob to about 3:00
position to return it to a mid-scale reading. Switching to controller B
gave me a momentary scare – the engine quit, well completely lost power for
the fraction of a second that it took to switch back to A. More on this
below.
Adding the snubbers on the
injector circuits resulted in quite a different profile on the mixture table
settings. It also resulted in smoother running at low rpm, and seemingly
easier tuning to get smooth transition from ‘low’ to ‘high’ table, and across
the stage point (or maybe I’m just getting better re-tuning).
One thing I had discovered when
re-tuning was that, apparently due to powering up the unit on the bench to
check the MAP sensor, resulted in the injector pulse setting (mode 3) to get
set to a much lower value, and the stage point to someplace out of range.
The engine would only run with the cold start switch on. Once I
got those things straightened out, things proceeded smoothly. When I had
all well on controller A, I did the copy A to B. Prior to flying, I had not
checked running on B. (OK, it’s on my check list, I just bypassed it.) After
the episode in the air I figured out that B was acting like A did before the
retuning. I tried multiple times again to copy A to B; but it did not take.
I had to manually retune B to get things running right. Don’t know
what, but the copy A to B is not working.
Didn’t mean to run on here – am
I boring anyone yetJ?
Expect to fly tomorrow for some
air pressure measurements on the oil cooler.
Al