Al,
Good catch on the voltage! Chris shouldn’t tune without the
alternator on.
The rpm indication could be crosstalk if the power wires are not
shielded and are in a conduit with other wires. The low voltage combined
with the voltage loss with the small wires in a long run will slow the
injectors down and make tuning very difficult.
No telling what would be the result.
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Al Gietzen
Sent: Saturday, June 27, 2009
11:32 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: More
progress, more questions....
I
am concerned about some sputtering that is present around idle. It is
generally
pretty smooth, but sputters too. Not sure what is causing it
yet.
Thoughts?
Don’t know
exactly you definition of sputtering, But could be a combination of factors,
including some mixture tuning required. My engine is smooth down to about 1500,
then begins to miss the occasional beat as I slow it further, and gets a bit
rough down at 1000. It might help if you can figure out why you have to
‘pump’ the throttle to make it slow down.
I don’t have a
clue about the RPM inconsistency, but on the photo of the EM2 panel it looks
like voltage is 11.1, but can’t tell for sure. Did you not have the
field current on the alternator? If you tune the engine with the voltage at about
14.0; then run at 11, it will be out of tune, and probably idle rough. This
becomes more of an issue with the small power wires and associated voltage
drop.
Next,
in the documentation for the EC2, the diagrams and part of the
text
it shows that most of the wires should be run using 22 and/or 20
AWG
wire for the connections. However, in ONE place in the document it
states
that the power wire to the coils should be 16 AWG.
I don’t think
that’s an inconsistency, perhaps a misunderstanding. I think the 22
and 20 ga. refers to all the wiring between the PCM and the EC2; The power
leads to the coils and injectors are a separate issue. As Ed points out, there
will be undesirable voltage drop in a 20 ga, perhaps worse than Ed mentioned
because the peak currents, especially for the injectors, will be greater than
10A. I’d also be a bit concerned about the heating in the wires
enclosed in a tube; although I’m not sure what the ‘average’
current is. If it is 10 amps the 20 ga. is going to get warm up; which
increases the resistance, etc. I know it’s a PITA; but if it were
me, I’d bite the bullet and change to 16 ga.
Oh,
a final comment on progress. My cooling continues to impress me.
I’m impressed
with your cooling as well. Mine is good now, but I had to make a few
changes after first flight to get it there.
Poco a poco, se va
lejos,
Al