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.