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From: "DaveLeonard" <daveleonard@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Flickering Faltering F$%(@$% Fixed
Date: Fri, 24 Sep 2004 23:27:25 -0700
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Like many, I have been plagued by a rough idle.  Today it is fixed.

The little electrical gremlins that pop up were starting to drive me crazy.
One landing light sometimes comes on when it is turned off, and last night I
discovered that the nav lights don't stay on.  After about 15 min. of
running the engine on the ground the micro relay in my controlvision EXP
BUSS II must get overheated because the nav lights went out.  Turning them
off for a few seconds (resetting the micro relay) would allow them to come
on briefly before going out again.

Then the strobe did the same thing.  Now that I think back, it turns out
that every time I fly the strobes have been turning themselves off shortly
after starting the flight but I just never took notice. (while the landing
light turns itself on).  It seems that the circuits on the EXP Buss can not
really handle their rated power very well.  Those were supposed to be 7 amp
circuits which is a little more than the draw, but the circuit was only able
to last for about 10 min.

Then it hit me - The alternator is using an OV protected 5Amp circuit from
the same board. and the lights really seem to sort of flicker (have tried
about 10 different useless solutions for that one).

Anyway, the excitation current for the alternator must be right at about 5
amps.  Turns out the micro relay has been tripping, then resetting itself
2-3 times /sec. Turning the alternator on and off with it.  The poor voltage
regulator must have been working overtime as my buss voltage read a steady
14.2V.  The fluctuations were too fast to register on the voltmeter.  The
voltage must have been going from battery voltage up to about 16+ volts to
maintain the average of 14V read by the meter.  As you can guess,
electronics don't like that kind of thing - but most things worked
surprisingly well.

I bypassed the stupid circuit board and connected the alternator field
directly to the alt output.  Wow what a difference.  The EC2 and fuel pumps
were probably the most affected.  All of a sudden I can get idle out of the
ultra rich and put the mixture right.  Idle is MUCH better.  I even had to
reset the idle stop so I could idle lower.  Down to 1000 RPM or less now and
it sounds great.  Oh, the lights stopped flickering and the radios sound
better too.  Go figure.

Dave Leonard