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krea.ellis(at)gmail.com
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 Posted: Mon Jan 27, 2020 4:10 am Post subject: Z-14 implementation for electrically dependent engine |
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First post. Thanks for considering my dilemma.
Installing dual ECU SDS fuel injection and ignition on a 6 cylinder Lycoming on an RV-10.
Design goal was for independent busses for each “channel” of SDS. Easy to achieve for fuel pumps, ECU’s and coil packs. Not easy for fuel injector power. In normal mode, each ECU only controls half (three) fuel injectors. Injectors are ground triggered by the ECU, power to all injectors comes from the airframe bus(ses), not the ECU’s.
Was trying to avoid have power for injectors going through a single switch. Other option is a diode fed/protected “injector bus” but this creates failure modes as well.
So is power through an appropriately rated Honeywell TL switch more reliable/redundant than the diode fed bus?
Any other suggestions as to how to provide redundant power to all 6 fuel injectors?
Thanks much!
Krea Ellis
Sent from my iPad
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ceengland7(at)gmail.com
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| Posted: Mon Jan 27, 2020 9:31 am Post subject: Z-14 implementation for electrically dependent engine |
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On Mon, Jan 27, 2020 at 6:15 AM Krea Ellis <krea.ellis(at)gmail.com> wrote:
[quote]
First post. Thanks for considering my dilemma.
Installing dual ECU SDS fuel injection and ignition on a 6 cylinder
Lycoming on an RV-10.
Design goal was for independent busses for each “channel” of SDS. Easy to
achieve for fuel pumps, ECU’s and coil packs. Not easy for fuel injector
power. In normal mode, each ECU only controls half (three) fuel injectors
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foghorn757(at)gmail.com
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| Posted: Mon Jan 27, 2020 11:49 am Post subject: Z-14 implementation for electrically dependent engine |
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The SDS diagrams show a single “ENG” bus powering the system. I believe this bus should be powered from the battery bus to insure no interruption in power if you have an alternator failure. SDS also recommends a standby battery that isn’t apart of the electrical system and runs through a 30A switch for emergency power. Many ways to skin this cat.
As to the relays and injectors. It’s my understanding (4 cylinder engines) that the dual ECUs connect to 2 injector relays. Each relay drives two injectors. If the primary ECU has a fault there is a switch to change to the Alternate ECU, which will continue to fire all 4 injectors. I haven’t read the 6 cylinder manual but it’s available for free at www.sdsefi.com.
Jeff Parker757-817-4929
| Quote: | On Jan 27, 2020, at 11:37, Charlie England <ceengland7(at)gmail.com> wrote:
On Mon, Jan 27, 2020 at 6:15 AM Krea Ellis <krea.ellis(at)gmail.com (krea.ellis(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: Krea Ellis <krea.ellis(at)gmail.com (krea.ellis(at)gmail.com)>
First post. Thanks for considering my dilemma.
Installing dual ECU SDS fuel injection and ignition on a 6 cylinder Lycoming on an RV-10.
Design goal was for independent busses for each “channel” of SDS. Easy to achieve for fuel pumps, ECU’s and coil packs. Not easy for fuel injector power. In normal mode, each ECU only controls half (three) fuel injectors. Injectors are ground triggered by the ECU, power to all injectors comes from the airframe bus(ses), not the ECU’s.
Was trying to avoid have power for injectors going through a single switch. Other option is a diode fed/protected “injector bus” but this creates failure modes as well.
So is power through an appropriately rated Honeywell TL switch more reliable/redundant than the diode fed bus?
Any other suggestions as to how to provide redundant power to all 6 fuel injectors?
Thanks much!
Krea Ellis |
I can offer some of the choices I made for a different automotive-style injection system, for your consideration. My dual controller system and all associated components are powered by a single 'engine bus', which is separate from any other a/c bus. The engine bus can be powered either directly from the battery, via a heavy duty switch, or from the plane's main power bus, via another heavy duty switch. The entire a/c can be powered down without affecting the engine, similar to a 'traditional' a/c engine installation. Each injector (and each individual coil) has its own fused supply from the engine bus. Assuming a 'best practices' installation of the engine bus and its supply circuits, the odds of losing the entire bus should be about the same as airframe structural failure. Individual components fed by the bus are protected by fuses, so no single component or wire failure should be able to take down the entire bus.
The controller has too many other design choices to cover here, but the short version is that the engine can be made to run at near full power with the loss of just about any one thing, short of total electrical failure.
While I'm aware of SDS' products, I'm not intimately familiar with how they handle failed subsystems. Are you saying that if you lose a controller, there's no way to drive that bank of injectors from the other controller? That does not sound like a system that would keep me happy at all. Losing half the engine's cylinders means losing *far* more than half its performance, not unlike a twin losing an engine. Will a fully loaded -10 be able to climb safely on significantly less than 50% power? It sounds like the designer chose the loss of half the engine, over the choice of losing a single cylinder if a relay failed.
To recap, my choice would be to supply all the injectors' power with individually fused circuits from a single, well conceived and installed bus, with redundant power sources. Your choices might be different, of course.
Charlie
(Mazda Renesis/RWS controller installation in progress)
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johnbright
Joined: 14 Dec 2011
Posts: 166
Location: Newport News, VA
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| Posted: Mon Jan 27, 2020 3:49 pm Post subject: Re: Z-14 implementation for electrically dependent engine |
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SDS six cylinder dual ECU system IS capable of driving all six injectors with one ECU. When they are driven by both ECUs, three on primary ECU and three on backup ECU, the ECUs are capable of trimming duty cycles to make all six A/F ratios the same. There is a three-position switch on the IP... pri/normal/bak... normal is for matched A/F ratios, pri or bak puts all six injectors on one ECU and the engine runs fine just LOP is not going to work well because EGTs will not peak at the same time.
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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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