I'm planning a dual SDS ignition and injection system for my RV-14's IO-390. While not absolutely set on this, I am planning to use the Vertical Power Primary Power System and VP-X Pro in a dual-alternator, "single" battery system. I would also use the SDS backup battery that Ross is planning for the EM-6 and a TCW 6Ah IBBS and a G5 with internal battery for avionics backup.
For further redundancy, I am considering an emergency bus contactor direct from the main battery that would power one fuel pump and one ECU (with the others being powered as necessary from the SDS battery). I haven't gone through various failure scenarios yet and I'm sure that will impact this decision, but I'm wondering just how I will switch the power to the pumps and ECUs. Under normal operation, I believe that both pumps and ECUs would be powered by the main bus through the VP-X. But, with two fuel pumps and two ECUs each having two possible power sources, I'm wondering about the possible proliferation of switches. Besides selecting a power source for each, there's the matter of selecting one fuel pump or the other and, possibly, removing power from one ECU (is this ever done? I haven't studied these systems enough to answer that). I envision, first of all, two switches selecting main or backup power for each side of the engine system. But, each of those has to control both a fuel pump and an ECU (DPDT won't cut it, right?). Then there would be two 3-position selector switches: fuel pump main/both/stby and ECU1/both/ECU2.
If there's a system that will drive me mad in this build, it will be the electrical system!
For further redundancy, I am considering an emergency bus contactor direct from the main battery that would power one fuel pump and one ECU (with the others being powered as necessary from the SDS battery). I haven't gone through various failure scenarios yet and I'm sure that will impact this decision, but I'm wondering just how I will switch the power to the pumps and ECUs. Under normal operation, I believe that both pumps and ECUs would be powered by the main bus through the VP-X. But, with two fuel pumps and two ECUs each having two possible power sources, I'm wondering about the possible proliferation of switches. Besides selecting a power source for each, there's the matter of selecting one fuel pump or the other and, possibly, removing power from one ECU (is this ever done? I haven't studied these systems enough to answer that). I envision, first of all, two switches selecting main or backup power for each side of the engine system. But, each of those has to control both a fuel pump and an ECU (DPDT won't cut it, right?). Then there would be two 3-position selector switches: fuel pump main/both/stby and ECU1/both/ECU2.
If there's a system that will drive me mad in this build, it will be the electrical system!