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