rmartingt
Well Known Member
So I'm getting closer to being able to start my systems installation and hoping to make some progress on my electrical diagram while I'm laid up next week. I've been looking over some thoughts on electrical systems and trying to figure out how best to go about providing reliable power to an SDS EFI system on an IFR-equipped aircraft.
I've done all my planning around the idea of a dual-battery, dual-alternator system--effectively, the Nuckolls Z-14, albeit with minor changes to the cross-tie wiring and switching (I don't want my start switch and crosstie switch combined), and adding some form of ground power input.
Under such a system, I'd wire half of the EFI directly to each of the battery buses, with a fuse and a switch for each component. However, this leaves me with at least 10 switches just for the engine components, as I'd have to have some way of turning them all off. Unless the coils, injectors, and injector relay don't draw power at all when they aren't firing? This also means I lose power to half the injectors if a whole bus goes down, and I don't think that would be a good thing for the engine.
Now, I also considered taking the same basic system, but instead of splitting items among two buses, I'd have them feed a single "engine bus" through a diode arrangement straight off the batteries. This reduces problems of having to deal with "which bus is powering things" but adds parasitic drain from the diodes and still keeps all the switches.
A variation on that would be to put a switch in line between each battery and the engine bus and keep the diodes; this would eliminate a lot of the individual component switches and leave me with just the fuel pumps. Everything else would be on whenever engine power was on.
I will try to get some block diagrams up soon to illustrate these ideas, but for now, does anyone have feedback so far?
I've done all my planning around the idea of a dual-battery, dual-alternator system--effectively, the Nuckolls Z-14, albeit with minor changes to the cross-tie wiring and switching (I don't want my start switch and crosstie switch combined), and adding some form of ground power input.
Under such a system, I'd wire half of the EFI directly to each of the battery buses, with a fuse and a switch for each component. However, this leaves me with at least 10 switches just for the engine components, as I'd have to have some way of turning them all off. Unless the coils, injectors, and injector relay don't draw power at all when they aren't firing? This also means I lose power to half the injectors if a whole bus goes down, and I don't think that would be a good thing for the engine.
Now, I also considered taking the same basic system, but instead of splitting items among two buses, I'd have them feed a single "engine bus" through a diode arrangement straight off the batteries. This reduces problems of having to deal with "which bus is powering things" but adds parasitic drain from the diodes and still keeps all the switches.
A variation on that would be to put a switch in line between each battery and the engine bus and keep the diodes; this would eliminate a lot of the individual component switches and leave me with just the fuel pumps. Everything else would be on whenever engine power was on.
I will try to get some block diagrams up soon to illustrate these ideas, but for now, does anyone have feedback so far?