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1. 08:12 AM - Re: Looking for help finalysing my Cozy's electrical system (johnbright)
2. 08:34 AM - Re: Re: Looking for help finalysing my Cozy's electrical system (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Looking for help finalysing my Cozy's electrical |
system
Re v1.04 and v2.11
Hi Eric,
I mis-spoke about switching power to EB 1 and EB 2 with relays to meet FAR 23.1361.
You already meet FAR 23.1361 with the two battery contactors.
When I was considering Z-14 for my SDS EFI+I equipped RV-6A, I wanted to be able
to kill both battery contactors in a smoke in the cockpit situation and still
have the engine running:
This led to an always hot engine bus diode OR'd from both batteries.
If you would like to reference my Z-14, it is called "Electrical Schematic RV-6A
with SDS dual EM-5-F rev G" in the Archive folder of my files.
SDS requires coilpack power to be switched whereas EFII has the P-lead input to
the ECUs. For FAR 23.1361 you could leave the P-leads unconnected and relay switch
the coilpacks.
The always hot nature of the engine bus and the items attached to it that are not
relay switched presents a danger in service and crash scenarios. With Z-101
the only thing always hot that's remote from the battery is the backup alternator
and one could choose to add a relay to it.
--------
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
https://drive.google.com/drive/folders/1u6GeZo6pmBWsKykLNVQMvu4o1VEVyP4K
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496617#496617
Message 2
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| Subject: | Re: Looking for help finalysing my Cozy's electrical |
system
At 11:39 PM 5/31/2020, you wrote:
><john_s_bright@yahoo.com>
>
>Single points of failure:
>All four injectors are powered by one reley, wire, and fuse link.
>Both pumps are powered thru the same switch.
Agreed. Will the engine run if one injector
becomes inop? Suggest separate switches for
each fuel pump. Ditch the 'auto' feature'
>Questions:
>The injectors have fuse links in the harness. Are they sized so they
>won't pop the one fuse link that feeds all four injectors?
>What happens if both injector enable inputs are un-grounded?
>Why are there relays for removing power from the coils?
Strive to reduce relays to minimum. I recall
seeing this installation published somewhere.
http://aeroelectric.com/Pictures/Misc/Too_Many_Relays.jpg
. . . mind boggling.
>What is the EFII Syst 32 Inj Pwr Module? I would have thought each
>ECU box has open collector injector drivers inside.
>Will the automatic aux pump feature result in a relaxation
>oscillator? (No pressure, pump on... now we have pressure, pump off, repeat.)
>Where are the batteries located?
>Thoughts/IMO:
>It would be simpler to have separate toggle switches for left and
>right coil "P-Leads".
Agreed
>It wouild be simpler to have an SPDT switch for injector enable
>grounds like EFII illustrates but what is the effect if the ground
>is lost to both injector enables?
Something to sort out . . . potential
single point of failure.
>I don't know how to have faith in Bus Manager (I know you mentioned
>you are not using Bus Manager) or EFII in general when they show
>un-necessary SPOFs that will stop the engine. Ref EFII Dwg 9 rev
>5/19 that you attached.
How about a Z101 engine bus? It's already
managed.
>50A is more than an engine bus requires. I am planning on dual four
>cylinder SDS EFI+I on O-360 and my calculations show:
>ECU 0.13A
Agreed
>Coilpack 1.1A at cruise
>Fuel pump 5.25A at 45 PSI (Walbro GSL393)
>14.5 Ohm injectors 0.32A each at cruise (32% duty cycle, 10 GPH)
>I plan to put both EFI+I systems (pri and bak) on one engine bus and
>the current draw is less than 20A (15A with both pumps and coils
>running for low altitude; 8.2A with one coil and one pump running in
>current conservation mode).
>I'm planning on an adaptation of Z-101 which is simpler than Z-14
>and IMO just as reliable.
>It would be simpler and more reliable to have separate toggle
>switches for the main and aux fuel pumps and eliminate the fuel
>pressure switch.
>The fuel pressure switch is called NO; I would think that means it
>is open when there is no fuel pressure so the logic is backwards.
>You mentioned dwg 1.04 but attached 1.00.
Wire and fusing sizes depicted are
not clear as to design goals. Diode
-ored power sources should locate
diodes at the load end of each feed.
As shown, faults downstream of diodes
would take out both feeders. Fusible
links are not useful here . . . in fact,
any fault that would open a fusible link
would take out both fuses.
The drawing is exceedingly 'busy'. A three
source, dual feed engine bus can replace
un-necessary 'redundancy' . . . offers opportunity
for each load to enjoy its own protected
feeder thus maximizing failure tolerance
while reducing system costs, weight and parts
count.
Bob . . .
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