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Well, time for some followup.
My 1st draft for circuit protection looked a lot like what Steve
describes (thanks, Steve), with individual fuses for virtually
everything, including an individual fuse for each injector and
each ignition coil. After ruminating over the actual loads for the
injectors & coils, I'm having second thoughts. The GM coil
harness I have in hand has a single DC power wire for all four
coils that it feeds (obviously isn't a part intended for flight,
but included in Tracy's installation manual).
The obvious concern is whether an individual coil or injector
failure has a statistically significant risk of taking out the
power supply that's fused for the total load. If there's no
statistically significant danger, weight & complexity could be
reduced by feeding the coils and injectors as groups.
So, is there any consensus on how to handle injector & coil
wiring? IIRC, there have been some coil failures in flight; were
those planes wired with a single fuse/breaker protecting all the
coils, or with individual fuses/breakers for each coil? What about
the injectors?
Any failure modes I'm missing? (other than a dead short on a
supply wire, of course)
Thanks,
Charlie
On 7/1/2014 10:13 PM, Stephen Izett wrote:
Charlie
Don’t know if it is wise but I have wired our electron
traffic management as follows:
1. A Main 32 way blade fuse block which is broken into two
busses: A & B being -
(The blade fuse block enables me to patch a current meter to
any circuit to see whats happening. Helpful when setting up or
trouble shooting but just nice and compact otherwise BUT I can’t
just re-energise a circuit like with circuit breakers, though
blade size circuit brakes do exist nowadays. This main fuse
block is mounted directly below main system switches so is very
accessible)
A. FLIGHT CRITICAL (16 fuses) fed by a keyswitch:
EC2(A), EC2(B), EM3, O2, Prop Pitch, Engine Fuel Pres Pump,
Engine Backup Fuel Pres Pump, Fuel Transfer Pump, Backup Fuel
Transfer Pump, Pri Fuel Injectors, Sec Fuel Injectors, Leading
Coils, Trailing Coils.
Notes 1. All engine fuel is fed from a header tank of 8
gallons with the transfer pumps feeding the header from the main
wing tank
Note 2. Separate power and return feeds to Pri and Sec Inj
& Leading and Trailing Coils, fuel pumps.
B. AVIONONICS (16 fuses) feb by Avionoics master switch:
RHS Dynon EFIS, FHS Dynon EFIS, Flight Computer of my own,
Com Radio, Transponder, Autopilot servos, Position Lights,
Strobe Lights etc,
C. LANDING GEAR PUMP switched through seperate breaker (this
mongrel draws ~30 amps)
Our airplane is plastic so return lines are very important.
We have separate main return paths - quiet and noisy.
Steve
Wow, Steve, that's great
detailed info; I was just hoping to get the total. I was
expecting the injectors to draw more than the coils, but
with all the coils together under 5 amps (and even
better for the injectors), then my wiring architecture
can get a lot simpler.
Many thanks,
Charlie
On 7/1/2014 7:19 PM, steve Izett wrote:
Hi Charlie
I think these are in the ball park but not measured
under flying conditions only idle.
ENGINE
EC2
.3
EM3
.5
COILS (D585)
5
INJECTORS (Renesis)
2
FUEL PRESSURE PUMP
x 1 8.4
FUEL TRANSFER PUMP x
1 1.6
O2
SENSOR 0.6
Total
Engine 18.4
Steve Izett
Has anyone with an ammeter
installed measured their engine's actual current
draw (controller, injectors, plugs, fuel pump)
with everything but the engine shut down, and
the alternator offline? IIRC, Bernie Kerr once
did a battery duration test & discontinued
after ~40 minutes, but I don't recall seeing any
actual current measurements.
Thanks,
Charlie
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