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SDS EFI+EI six cylinder injector power Z-14 no diodes

 
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johnbright



Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA

PostPosted: Fri Feb 28, 2020 7:22 pm    Post subject: SDS EFI+EI six cylinder injector power Z-14 no diodes Reply with quote

Posting this on behalf of Krea Ellis:

======================

Some of us with 6 cylinder engines and planning on Z-14 and SDS EFI+EI dual ECUs have been looking for a way to provide dual power paths to the fuel injectors without using a diode-fed engine bus. It is easy to power the primary and backup ECUs, coilpacks, and fuel pumps from separate buses but there is only one set of injectors.

I suggested to Ross and Barry at SDS that an arrangement similar to the relay box already supplied and required for the dual ECU 6 cylinder system would be a good starting point to provide a dual power path. This discussion has led to a slightly modified relay box with an additional daughter board and no new moving parts.

This new version relay box will provide singe-switch control of injector minus-side connections to the ECUs' drivers AND injector positive-side connections to separate power buses.

In the NORMAL switch position the injector relay coils are un-powered and injectors 1, 2, and 3 are driven by the primary ECU while injectors 4, 5 and 6 are driven by the backup ECU (this facilitates cylinder trimming for equalizing A/F ratios in each cylinder). In the PRIMARY switch position all six injectors are driven by the primary ECU. In the BACKUP switch position all six injectors are driven by the backup ECU. This scheme does not change with the modified relay box. Note that injectors are driven to ground by the drivers in the ECUs but are not powered by the ECUs.

The modification passes power to the injectors the same way, instead of having all six of them connected to an engine bus. When the switch (which will now be DPDT) is in the NORMAL position, injectors 1, 2, and 3 are powered by the #1 bus and injectors 4, 5, and 6 are powered by the #2 bus. When the switch is in the PRIMARY position, all six injectors are powered by the #1 bus. When the switch is in the BACKUP position, all six injectors are powered from the #2 bus.

So, no diodes and no additional relays beyond those already required for SDS.

If you want your relay box modified, reach out to Ross or Barry at SDS. I’m pretty excited about this development as it meets all of my original design goals for my SDS equipped RV-10.

Krea Ellis

================

Drafted by Krea Ellis and final edited by John Bright


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_________________
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
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