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Keep in mind that there are entire books written on the subject of aircraft
wiring so this will not be an exhaustive answer and there are always situations
which I won't think of until something goes wrong (like Al's situation with the
remote EM2 display and the EC2 PCM wiring).
The only shielded wire in my system is the alternator cable to the
battery (mainly for radio noise suppression) so extensive use of shielded wires
is usually not required. I did use a twisted pair for the crank angle
sensor on the Renesis.
Here is the general guideline on the EC2 wire routing outlined in the
EC2 installation guide that I should go back and expand on, clarify,
etc.
Route the low level control lines (PCM, crank
sensor, coil control lines, etc) separately from any high current switching
lines (coil power, coil ground, injector power & drive lines,
etc).
That's it. As stated above, there will always be possible
exceptions like Al's situation but 99% of the time this general rule will work
fine.
Tracy (back to getting the 20B setup to run for the Rotary
fly-in)
----- Original Message -----
Sent: Sunday, October 15, 2006 8:35
AM
Subject: [FlyRotary] Coil Wiring
Tracy,
I have both my harneses (EC &EM-2) soldered up
and ready to be routed.
I would like to do this once and
correctly...:>)
I have two firewall penetrations, one on the pilot
side going to the
injectors with the injector control wires bundled
together. I had
planned to bring the injector power wires thru this
same penetration
bundled together, but not bundled with the control
wires. If I need to
do any twisted pairs, exactly which pairs should
be twisted together??
How far apart should the two bundles be?
The
other firewall penetration is on the copilot side. I currently
have
the balance of the EC-2 wires bundled together and going thru
this
penetration. I also have all the EM-2 wires bundled and going
thru this
same penetration. This includes therrocouple and
temperature sensor
wires. Sounds like I need to separate some
wires. If so which wires
need to be separated and how? Do
I need more penetrations? Exactly
which wires need to be twisted
together and or shielded?? How far apart
should the bundles be and if
they are together (penetrations) how far
can they be allowed to be
close?
Thanks,
Bill Bradburry
Mark;
Tracy;
I'd like to explore this further. Mark S
wrote:
After reading Bob Darrah's post last week where he noticed a
big
improvement after separating the leads to his coils I gave it a try
on
my 20B. It made a big difference, but was most noticeable in the
lower
rpm range. I was only able to separate the wires down near the
coils,
and then only by a small amount, but it made a substantial
improvement.
My question for Tracy is, can I leave the grounds and +14v
wires bundled
together and only separate the trigger leads, or do I need to
separate
all the wires? Also, if I were to use 3 individual shielded
wires and
ground the shields, could I then bundle the trigger leads
together with
the rest of the coil wires?
On a side note,
after separating the coil leads, it took a much leaner
mixture to get it to
run smooth. Before, the best it would idle was
about 1200rpm, now it
will idle nicely at 900 rpm, not that I want to do
that, but it shows that
the improvement isn't all in my head.
Clarify for me which
leads you separated; the control leads from pins 3,
20, and 21 (C-pins)
from each other? I find that below about 1400-1500
rpm the engine
begins the occasional miss, and gets progressively
rougher as rpm
decreases. I've been thinking that it seemed more
ignition related
then mixture related.
I have the C-pin leads and the B-pins
ground bundled together from the
box to the firewall penetration (a few
feet). These bundles are separate
for each set of coils (lead,
trail). From the firewall to coils (a few
more feet) the power lead
(pin-D) joins the bundle. The A-pins are all
grounded at the coil
mount.
Tracy wrote:
1. How long is the wiring
harness between EC2 and coils?
About 6 ft for the trailing and 10 ft
for the leading.
2. How is the power ground to the coils
(A terminals) routed?
(hopefully not in the same harness, if so, there is
your problem).
3. Same question as 2. on the power
terminals.
Does this say that the power lead (D-pins) should not be
bundled with
the C or B pin leads? If so, is this just as true if the
lead and
trailing bundles are separate.
4. I would be
surprised if this turned out to be the problem but if
coupling between the
control lines themselves (C pins) turns out to be
the problem, use
either twisted pairs or shielded wires to drive the B
& C lines to each
coil. I would lean toward twisted pairs.
I ran a common B-pin
ground for each set; bundled with the C-pin leads
but not twisted.
Twisted pairs would mean adding more wires - or would
twisting 3 control
leads with one ground to as well?
5. Are there any other
lines routed along with the coil harness
(injector drives, etc)?
The
coil bundles run with the injector drive bundles from the near the
firewall
to the top of the engine, maybe 4 ft or so; and run with other
wires for a
foot or so. One objective is to minimize firewall
penetrations,
another is to maintain separation between sets of
injectors and sets of
coils for true redundancy, and another is to
separate noisy wires from
quiet wires; so further separating isn't a
simple
matter.
Al
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