Joe;
Gees, that’s a
weird one.
I assume from your
note that problem is no ignition trigger pulse, and that the injectors are
firing. Have you determined where the signal is being interrupted?
Is the loss of signal from the CAS, or out of the
EC2? The capacitor grounded to the engine will be inducing some sort of
opposite signal to ground – maybe affecting the CAS? Just some
WAG.
I have no filter on
the alternator output – never saw more than the normal ripple there. Could a
failed diode in the output converter be making big spikes? Wait – even with
alt off, no start? What’s in the ‘alt filter’ besides a capacitor? Is the
filter in the circuit when you run the external wire?
Just a few random
thoughts – I expect you know more than I about how this stuff
works.
Al
G
-----Original
Message-----
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Joe Ewen
Sent: Friday, January 15, 2010 3:13
PM
To: Rotary motors in
aircraft
Subject: [FlyRotary]
Alternator Filter
I have been having problems with
my engine installation. Starts, runs great - turn on the alternator and
the engine starts to miss. Put a scope on R1 ignition trigger lead and
sure enough missing trigger pulses. Turn alternator off no more
missing pulses. Looked at the alternator output with the scope and as
expected saw some spikes. Bought an aircraft spruce alternator
filter. Ran the engine , worked fine until it would not prime or run any
more. That turned out to be a defective store switch. Replaced the
switch and back to normal. Here is the part I do not yet
understand.
Engine runs fine, added alternator
filter and can not even get a pop. Take the filter off, starts
fine. Filter back on (alt off), no joy. Filter on (alt on), no
joy. Filter off, runs fine. I can not imagine how a filter
capacitor is interfering with the ignition of the controller. If anyone
has any insight please feel to speak up.
I have 2 wiring ducts: 1. quiet -
signals such as to the PCM, ignition firing leads, low voltage sensor, analog
signals. 2. Noisy side, battery cables, ignition power, injector power
and signal (twisted pair shielded (shield properly
grounded.)
Alternator connects to battery
cable at the starter. If I run an external wire between the alternator
and the battery (outside the airframe, long wire - engine in back, battery in
front (canard)) everything runs fine.) Aesthetically this might not be a
good approach, not to mention the aerodynamic impact.
This problem has kicked my butt
this week working on it in the cool 20F evening air. Any insight is
appreciated, especially why a capacitor (which does not conduct DC) would
render the EC2 controller inoperative would be
appreciated.