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Power system architecture for EFI

I will be ordering an EFI in a month or two, but I have spent more than 6 months trying to figure out how I want to wire it. My "dream" was to use an automotive relay and fuse panel. That is still my long term goal that may not be attained. My second choice was an aftermarket panel, which I now possess and am wiring up. Hopefully in the next few months I will have the time to figure out how to create a professional looking electrical system on a PC. Right now, not so much.

I am using a "Severe Service Vehicle" relay panel. Meant for construction equipment, off road vehicles, etc. All primary circuits will operate off of SPDT terminal 87A in their primary mode. NO relay operation required to run the engine. I will have a bank of micro switches to energize the relay coil and switch the relay to terminal 87, which will shut off the circuit. These switches will allow me to shut off fuel pump 1 or 2, ignition 1 or 2, or alt 1 or 2. If any or all of these switches, or their power source fail, no problem. The engine runs. They exist to check the function of the backup, or select the backup. Each function has its own circuit. No A/B switches.

The panel uses Delphi sealed connectors, and the whole panel is IP 66 or 67 for moisture and vibration. it is a little heavier than I would like at 3 pounds. But compared to a bunch of bus bars, etc, it might be a push. Maybe 550 to 600 bucks with all connectors and wire.

The power to the panel will comply with one of Nuckols wiring schemes.

Hopefully I get automotive reliability, with the ability to test backup functions, or switch to the backup. Like I said I would prefer to use a stock auto panel, but I haven't found one that I could easily switch functions "off" to check the backup.
 
Parallel diodes

A few pages ago I proposed paralleling diodes to put two batteries in parallel, hopefully making an engine bus more reliable. I was able to put the question to an automotive electrical designer. Here is his resopnse, which will definitely change my thoughts:

"I am suspicious of parallel operations. I have tried paralleling power supplies, coils, and transistors and due to imperfect matching things get hot due to oscillations: on and off and the switching causes heat. Getting the parallel devices to conduct equally is not easy. It also does not offer the same safety factor as having tested redundant components that can be switched out and in as needed. Some math analyses would be needed to verify this.

Another concern is that diodes can fail either open or short. I am not sure and will do some more thinking about the impact of a shorted diode. An open diode by itself would not be a problem, other than being able to detect and replace when back on the ground. What is not wanted is one battery draining into the other; one or both batteries might fail. To me a switching arrangement would be better. That is switching in and out either power system to either critical component set. The best would be on the ground checks, before air, of both power systems and both sets of critical components and then the capability of switching."
 
"is there no point inside that box where a single failure (bad solder joint? bad circuit element? metal chip? high-velocity projectile penetration?) can cause the essential bus to shut down? No place?"

The Bus Manager is plenty good enough for me to fly behind and I'm pretty picky about what keeps me in the air. And it's way better than any home brew solution I've ever had the privilege of reviewing. Our professional installers who have lots of experience with these parts use a Bus Manager - as do we.

Robert

That may be so. But it doesn't answer my question. How can you claim this to be a redundant system (triple redundant on your website) when its all in one box?

The "home brew solution" you are casting shade on is two switches and two diodes.
 
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Cliff, what your automotive electrical designer said about parallel diodes and etc is true. However, from what you wrote, it seems that he was trying to share the load between two parallel devices, not easy. But if each of the diodes is capable of carrying the full load independently of the other, then I see no problem of having two in parallel. I am not necessarily recommending two diodes in parallel, just saying that doing so does not create a problem. Mount diodes with heat conductive paste to help carry the heat away, and they should last a very long time.
 
Bus Manager

"That may be so. But it doesn't answer my question. How can you claim this to be a redundant system (triple redundant on your website) when its all in one box?"

Steve,
There are multiple current paths through the box - four as matter of fact.
Two from the batteries going through the internal normal ops bus relays and two through the emergency power switch.

Maybe we should call it "quad redundancy"?

The fact that "everything is in one box" is irrelevant. Everything in your plane is in one airframe - does that mean that nothing in it is redundant?

Robert
 
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I lost faith in Bus Manager when I saw it recommends both pumps share common wiring, circuit breaker, and relay.

https://drive.google.com/file/d/1JbifzXcWGVa1GCNFHbCWiy3Lvc9ni0Kb/view?usp=sharing

That?s an easy workaround. It?s simple to split that circuit up and incorporate two relays and two C.B.?s....that?s what I did. You can wire up any of the peripheral devices any way you like. In my case I?m incorporating two relays and two C.B.?s and I?ll let one toggle switch control the pumps...(off/(pump1/auto)/pump2. If you notice in the B.M.?s wiring schematic it doesn?t call for an off switch. If you follow those wiring directions exactly as shown it would have you pulling the breaker to turn the pumps off. I don?t like that aspect of the system so I have a three position toggle switch to give me better control of the pumps. Another example is the battery wiring. I?m using two batteries in my setup but only one of them will ever be used for starting and the other one....(which will be one of the smaller and lighter EarthX batteries)...will only be in place for redundant/backup power. This will allow me to not only remotely mount the backup battery but also limit its wire size (maybe 8 or 10g) because it won?t be being used for starting power. Also, doing it this way will allow me to eliminate the two starter solenoids that the schematic calls for. I plan on wiring the main battery cable directly to the starter and just using the starters own built in solenoid to engage the starter and this will all be done via the main/ battery/momentary start switch. The main point I?m trying to make in being a proponent of the bus manager is that if you take advantage of its primary function....which is to ?manage? your main and E-bus, you can then customize other aspects of it as you see fit. For me, I really like the fact that it can manage a led-acid and lithium battery together within the same system...which is typically a no-no. It allows for easy operation of batteries one ?or? two, or battery one ?and? two.....your choice of how to wire up your system. Another feature that I like is the automatic switching of fuel pumps 1 and 2 in the event of a sudden fuel pump failure/stoppage. I could go on and on about what I like about the bus manager but I think I?ve made my point. I think that if you look at its base/core function and architecture, it?s a box that works pretty well. I think that it?s fairly easy to modify and customize how the B.M. interacts with the rest of your wiring system and components. Could it be better and maybe even fool proof?....maybe so, but like I said, if you use it more for it?s base function and let it do it?s job, than I think it?s fairly easy to do any other modifications to your own personal wiring architecture that fits your personal needs. There are a lot of people here on the forum that are wiring gurus and I?m sure that they can design a wiring schematic that?s way better then the bus manager, but for a dummy like me I think it help me avoid a lot of mistakes that I could potentially make. Man, I didn?t intend on this post being this long when I started writing it. LOL!!

Mark
 
Careful

SNIP.... Also, doing it this way will allow me to eliminate the two starter solenoids that the schematic calls for. I plan on wiring the main battery cable directly to the starter and just using the starters own built in solenoid to engage the starter and this will all be done via the main/ battery/momentary start switch. .....SNIP

Mark

Recommend you retain the start solenoid, not just wire directly to the starter from the battery.

Don?t forget you will need to get the alternator charging current to your start battery. While you can connect it directly to the battery side of your start solenoid, you then have no way to disconnect it. If you connect it via your smaller relays for the other bussses, you will overload them (60+ amps is a boatload).

This leads to the logic for having a conventional master relay(s) between the battery(s) and the start solenoid.

On my planes the POH immediate action for any electrical fault is to open each battery master solenoid as this will isolate the most likely problems. The panel has separate 30 amp relays feeding power from each battery to that half of the panel so IFR flight continues as the pilot figures out what happened - or just lands to figure it out on the ground.

Carl
 
Recommend you retain the start solenoid, not just wire directly to the starter from the battery.

Don?t forget you will need to get the alternator charging current to your start battery. While you can connect it directly to the battery side of your start solenoid, you then have no way to disconnect it. If you connect it via your smaller relays for the other bussses, you will overload them (60+ amps is a boatload).

This leads to the logic for having a conventional master relay(s) between the battery(s) and the start solenoid.

On my planes the POH immediate action for any electrical fault is to open each battery master solenoid as this will isolate the most likely problems. The panel has separate 30 amp relays feeding power from each battery to that half of the panel so IFR flight continues as the pilot figures out what happened - or just lands to figure it out on the ground.

Carl

Great points!!
 
That?s an easy workaround. It?s simple to split that circuit up and incorporate two relays and two C.B.?s.... and I?ll let one toggle switch control the pumps...(off/(pump1/auto)/pump2.

If you are running dual feeds and CB's, and switching with a toggle switch, why would you need the relay at all?

In the linked schematic the relay is used to switch from one pump to the other while using a single feed from a single CB.
 
Mark,

A multi-throw toggle switch is yet another single point of failure. If it physically breaks (yes, it happens), you could lose both pumps.
 
If you are running dual feeds and CB's, and switching with a toggle switch, why would you need the relay at all?

In the linked schematic the relay is used to switch from one pump to the other while using a single feed from a single CB.

The way I?m planning on wiring it will incorporate some redundancy. On one relay I?ll have 87 connected to one pump and 87a connected to the other pump. On the second really I?ll do the exact same thing. This way the B.M. can do it?s thing with its automatic switching capabilities and if one of the paths of electricity is interrupted for any reason (C.B.,relay,etc.) the other C.B. and relay can take over full duty and continue to allow the B.M. to work as normal...including its automatic pump switching functions. So basically, 87 from both relays will go to one pump and 87a will go to the other pump....so I?ll have two relays and two different circuits/C.B. doing the job that one relay and one C.B. can do....but they will be a backup for each other in the event one of them were to fail. I?m also planning on incorporating an oil pressure sensor switch into the system so that while the toggle switch is in the pump1/auto position, and if there?s no oil pressure, the fuel pumps will automatically shut down. All modern automobiles have this safety feature built in, so that in an accident the fuel pumps don?t continue to run and possibly spray fuel everywhere. This safety feature/switch will only affect the system when the toggle switch is in the pump1/auto position. By flipping the switch into the pump 2 position everything will work as normal.

Mark
 
Mark,

A multi-throw toggle switch is yet another single point of failure. If it physically breaks (yes, it happens), you could lose both pumps.

That?s a great point....and well taken, but I?m using top quality mil-spec switches and I think the simplicity of a single switch has merit....but I have thought about your exact point quite a lot.

Mark
 
Well, even space-qualified stuff breaks. Surprisingly often.

One of the reasons I like the Aeroelectric Connection list so much is the basic philosophy that drives it. Bob emphasizes to not ask how reliable something is, but what happens when it breaks. If bad things would happen, then ask what could be done to create plan B. It's unreasonable to add spare wings, but an additional switch? Not hard at all. :)

Worst thing (and I struggle with this) is the added *operational* complexity. That's multiplied if some other pilot needs to fly the plane.

Charlie
 
Well, even space-qualified stuff breaks. Surprisingly often.

One of the reasons I like the Aeroelectric Connection list so much is the basic philosophy that drives it. Bob emphasizes to not ask how reliable something is, but what happens when it breaks. If bad things would happen, then ask what could be done to create plan B. It's unreasonable to add spare wings, but an additional switch? Not hard at all. :)

Worst thing (and I struggle with this) is the added *operational* complexity. That's multiplied if some other pilot needs to fly the plane.

Charlie

Charlie,

My thoughts exactly!!....including me trying to fiddle with more than one switch in the event of an emergency. Heck, I?ll be doing good just to drive the thing to a safe landing. LOL!! But you?re point is well taken regarding Bob?s line of thinking regarding ?what if?. I think the way I?m going to be able to wire it, it?ll default to one of the circuits to continue to be hot and at least one of the pumps to continue to run even if the toggle switch itself fails.

Mark
 
pump backup

"I lost faith in Bus Manager when I saw it recommends both pumps share common wiring, circuit breaker, and relay."

As already stated:
If you want further pump power redundancy, simply add a toggle switch with its own power source to one of the pump 12v terminals - pretty simple.

The automatic pump management of the Bus Manager is a very nice feature.
As is the start batt select feature, and of course the redundancy of the essential bus. You lose all of this going another route.

Robert
 
Robert;
Threads like this are the reason I am here. To learn. Very occasionally I might have something to add.

I am not a moderator, but to me your posts cross the line and actually detract from the thread.
 
svyolo

Hi Svyolo,
Sorry if we cross the line for you.

We have worked with more than 450 aircraft/builders now over the last 16 years.
Our only concern is safety. If we can help a few people avoid the mistakes that have been implemented before them, this is a well worthwhile effort in our estimation.

I fully realize that the din of opinion in internet forums can be overwhelming.
It is not always easy to discern the facts that sit between the endless lines of good intentions.

A very good place to start is to get information directly from suppliers who have been down these roads many times before and know their products well.

Robert
 
Our only concern is safety. If we can help a few people avoid the mistakes that have been implemented before them, this is a well worthwhile effort in our estimation....

A very good place to start is to get information directly from suppliers who have been down these roads many times before and know their products well.

Robert

Ok, so seriously....tell us what happened to these two.

https://app.ntsb.gov/pdfgenerator/R...D=20171031X10251&AKey=1&RType=Prelim&IType=LA

https://app.ntsb.gov/pdfgenerator/R...D=20161129X71536&AKey=1&RType=Prelim&IType=LA
 
NTSB

As far as I know:
1. Voltage regulator failure leading to over voltage, dual lithium battery installation melt down, electrical system failure.

2. Non standard wiring installation, too small of a circuit breaker used on the injector circuit, injector breaker popped during low level (river following flight), hard landing.

Robert
 
The way I?m planning on wiring it will incorporate some redundancy. On one relay I?ll have 87 connected to one pump and 87a connected to the other pump. On the second really I?ll do the exact same thing. This way the B.M. can do it?s thing with its automatic switching capabilities and if one of the paths of electricity is interrupted for any reason (C.B.,relay,etc.) the other C.B. and relay can take over full duty and continue to allow the B.M. to work as normal...including its automatic pump switching functions. So basically, 87 from both relays will go to one pump and 87a will go to the other pump....so I?ll have two relays and two different circuits/C.B. doing the job that one relay and one C.B. can do....but they will be a backup for each other in the event one of them were to fail. I?m also planning on incorporating an oil pressure sensor switch into the system so that while the toggle switch is in the pump1/auto position, and if there?s no oil pressure, the fuel pumps will automatically shut down. All modern automobiles have this safety feature built in, so that in an accident the fuel pumps don?t continue to run and possibly spray fuel everywhere. This safety feature/switch will only affect the system when the toggle switch is in the pump1/auto position. By flipping the switch into the pump 2 position everything will work as normal.

Mark

Although this was originally in reference to automobile racing-----it is often quoted in things aeronautical ........and rightly so.

SimplifyThenAddLightnesColinChapman44x44Final.png
 
As far as I know:
1. Voltage regulator failure leading to over voltage, dual lithium battery installation melt down, electrical system failure.

2. Non standard wiring installation, too small of a circuit breaker used on the injector circuit, injector breaker popped during low level (river following flight), hard landing.
Robert

Thank you. So what can you help us learn?

RV-6: Voltage regulator failure is pretty obvious, based on the pilot report of hot batteries and 15.5V at last check. We've been told EarthX batteries disconnect from charging at around 16.5 volts (but still have an output, however strange that may seem). Let's assume both batteries disconnected at 16.5V, a fair assumption because a meltdown wouldn't happen until failure of the battery management system at 60V or more. How would a battery charging disconnect result in an "electrical system failure" which would kill an EFI/EI? And of course, how might it be prevented?

Airborne Extreme: If I understand correctly, you're saying there was only one circuit breaker for all injectors. There is no standard wiring diagram in the EFII-brand manual. What do you recommend?
 
Although this was originally in reference to automobile racing-----it is often quoted in things aeronautical ........and rightly so.

SimplifyThenAddLightnesColinChapman44x44Final.png

Hey Mike,

Yes....my thoughts exactly!! I know that sometimes there can be a fine line and a hard balancing act between simplicity and added safety redundancy. In my description of how I plan on wiring up the fuel pumps, I ?think? that I?ve achieved that balance. I basically analyze the ?what if? situation and expanded my though process from there. I know that we can?t predict or prepare for every conceivable scenario, but this is how I visualized and hopefully rectified the possible weak links in the ?all electric fuel pump? architecture by incorporating a little bit of redundancy without adding ?too much? complexity. I won?t go into the strengths or weaknesses of the bus manager itself because there are many opinions...both good and bad, so I think it just boils down to ones own personal thoughts and opinions and comfort level with it. So, moving on past the B.M. itself, I asked myself these questions:

1. Q: What would happen if the single circuit/circuit breaker that ?both? pumps rely upon were to fail?
A: I would be a glider.
So what?s the fix? Split things up and incorporate ?two? circuits and ?two? circuit breakers. That?s step one in adding redundancy without introducing too much complexity.

2. Q: What would happen if the ?single? relay that ?both? fuel pumps rely upon were to fail?
A: Same as above...I?d become a glider. So what?s the fix? The same answer as above regarding the C.B?s. I?ll incorporate one additional relay and run them in parallel with each other so that if one were to fail the other one will take over full duty without there even being so much as a hiccup in normal operations. Once again, incorporating redundancy without introducing too much complexity.

3. Q: What would happen in a crash if a fuel line were to rupture and there?s still full power being supplied to the fuel pumps?
A: If I weren?t already dead, I?d surly die a fiery painful death. So what?s the fix? Incorporate a simple oil pressure sensor switch that?ll shut the fuel pumps off automatically if there no oil pressure present...ie. sudden prop/engine stoppage. Once again, very little complexity added as compared to the added safety margins.

4. Q: But what happens if the oil pressure safety switch discussed above were to fail?
A: The above discussed safety switch feature is only operational in the pump 1/auto toggle switch position...which is the primary pump that?s used during normal operations. The oil pressure safety switch feature is completely bypassed when the fuel pump selector switch is in the pump 2 position. So, if that oil pressure switch were to fail during flight it will be a simple flip if the selector switch into the pump 2 position and the flight will continue as normal.

So, even though I?m firmly in the ?keep it simple stupid? camp, I?m hoping that I?ve thought through a few possible ?what if? scenarios and have hopefully managed to incorporate a few extra safety features without introducing ?too much? complexity.

Mark
 
So.. to Mike's point, remind me again what real benefit does EFI/EI get you over standard Bendix style FI with lets say some Pmags?

Sounds to me like things are awfully complicated, kinda reminds me of the FADEC system that eventually got removed from my friends RV9 due to issues that couldn't seem to be resolved, airplane went back to std FI with EI, probably lost 10 lbs of "stuff" in the process, and ran perfectly after that.

I understand if you just love to "tweak", but personally I just like to be able to jump in the airplane and fly and not worry about the stuff under the cowl.
Simple, and it just works.
 
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We've been told EarthX batteries disconnect from charging at around 16.5 volts (but still have an output, however strange that may seem).

So, they may NOT have output, hopefully, the NTSB investigation will provide some enlightenment on the chain of causes.
 
So, they may NOT have output, hopefully, the NTSB investigation will provide some enlightenment on the chain of causes.

Even if both EarthX batteries disconnected themselves, the alternator is still there, with voltage at some high level.

As for the NTSB, I wouldn't hold your breath. Not a problem, given Robert's kind offer.

Our only concern is safety. If we can help a few people avoid the mistakes that have been implemented before them, this is a well worthwhile effort in our estimation...A very good place to start is to get information directly from suppliers who have been down these roads many times before and know their products well.

Robert
 
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So.. to Mike's point, remind me again what real benefit does EFI/EI get you over standard Bendix style FI with lets say some Pmags?

Sounds to me like things are awfully complicated, kinda reminds me of the FADEC system that eventually got removed from my friends RV9 due to issues that couldn't seem to be resolved, airplane went back to std FI with EI, probably lost 10 lbs of "stuff" in the process, and ran perfectly after that.

I understand if you just love to "tweak", but personally I just like to be able to jump in the airplane and fly and not worry about the stuff under the cowl.
Simple, and it just works.

While some people using certain brands of FADEC have had some or numerous problems, many due to poor design, severe complexity, software issues, wiring and lack of testing and fleet time etc., many using other brands of EFI have had few if any problems and have done no maintenance aside from checking spark plugs and fuel filter screens at annual. Some of these date back 20+ years now. http://www.vansairforce.com/community/showthread.php?t=147345 Two of our high timers have over 2000 hours each in the flight instruction field and zero problems as far as I'm aware.

It's the same idea as EFI in cars which revolutionized reliability compared to points and carbs- no or minimal maintenance and years of trouble free operation.

You get precise timing and mixture (in all cylinders) under all conditions, less bore washing, less chamber deposits, better cold and hot starting, better idle quality, lower mission fuel burn and less pilot workload. There are no more periodic inspections as on P Mags.

It's not hard to build a good, simple, redundant electrical system.

System weight is comparable to Bendix FI and a couple of mags.

None of this is new as some people think. Homebuilders have been using our EFI as far back as late 1995 and not to sound like a broken record but there are over 1900 of our aviation ECUs and systems out there, both in civilian and military use.

Nobody needs $30K worth of glass to fly day VFR either but that is the preference these days.

The engine builders, cowling makers, hose fab shops etc. are all getting on board now to service the growing number of customers who are installing EFI these days.
 
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So.. to Mike's point, remind me again what real benefit does EFI/EI get you over standard Bendix style FI with lets say some Pmags?

Sounds to me like things are awfully complicated, kinda reminds me of the FADEC system that eventually got removed from my friends RV9 due to issues that couldn't seem to be resolved, airplane went back to std FI with EI, probably lost 10 lbs of "stuff" in the process, and ran perfectly after that.

I understand if you just love to "tweak", but personally I just like to be able to jump in the airplane and fly and not worry about the stuff under the cowl.
Simple, and it just works.

Hey Walt,

Well, the best way that I know of how to answer your question is that I think that it just boils down to personal preferences and you just have to pick your poison. I think your question, which is VERY valid opens up a whole other discussion. I guess that I?m more in the ?modern technology? school of thought VS. the more old school traditional style of doing things. Don?t get me wrong, there?s absolutely nothing wrong with old school. I think that the beauty of an EFII or SDS type of system is that once you have it dialed in, it should be fly and forget. A computer (ECU) is going to do EXACTLY the same thing every time...where as I can?t do that manually. It?s very true that it?ll take some tweaking to get it dialed in correctly, but once it?s done, it?s done. A few things come to mind when considering an EFII or SDS system:

1. No moving parts...(other than the fuel pumps). I really like solid state!!

2. Having the ability to tweak each injector individually to get EGT?s/CHT?s even and happy.

3. Having the ability to adjust the timing perfectly in accordance with various RPM?s and manifold pressures, and to be able to do this weather running AvGas or MoGas.

4. Vapor lock is a thing of the past.

5. Better LOP operations.

These are just a few things that I can think of, but I?m sure there?s more. Like I said, there?s absolutely nothing wrong with old school and it?s served us well for a very long time, but I think once you get one of these electronic fuel injection and ignition systems dialed in it?ll be hard to beat.

Mark
 
Let's be careful

Hey Walt,

Well, the best way that I know of how to answer your question is that I think that it just boils down to personal preferences and you just have to pick your poison. I think your question, which is VERY valid opens up a whole other discussion. I guess that I?m more in the ?modern technology? school of thought VS. the more old school traditional style of doing things. Don?t get me wrong, there?s absolutely nothing wrong with old school. I think that the beauty of an EFII or SDS type of system is that once you have it dialed in, it should be fly and forget. A computer (ECU) is going to do EXACTLY the same thing every time...where as I can?t do that manually. It?s very true that it?ll take some tweaking to get it dialed in correctly, but once it?s done, it?s done. A few things come to mind when considering an EFII or SDS system:

1. No moving parts...(other than the fuel pumps). I really like solid state!!

2. Having the ability to tweak each injector individually to get EGT?s/CHT?s even and happy.

3. Having the ability to adjust the timing perfectly in accordance with various RPM?s and manifold pressures, and to be able to do this weather running AvGas or MoGas.

4. Vapor lock is a thing of the past.

5. Better LOP operations.

These are just a few things that I can think of, but I?m sure there?s more. Like I said, there?s absolutely nothing wrong with old school and it?s served us well for a very long time, but I think once you get one of these electronic fuel injection and ignition systems dialed in it?ll be hard to beat.

Mark

While I understand repeating product literature is normally a good thing, I would not want builders to think the objective of cylinder mixture control is to achieve a specific CHT or EGT. This is exactly wrong.

As been discussed on multiple posts, the specific EGT value means little as compared to fuel flow for each cylinder when that cylinder's EGT peaks (GAMI spread). The CHT value, while affected by fuel flow, is best used to verify normal operations, effective engine cooling air, and verify drop when LOP.

If using an EFII and tweaking to achieve a specific EGT or CHT value you will have the cylinders way out of balance.

So other thoughts reflecting on my operation of a balanced AFP injection system and pMags:
- Never had vapor lock
- Never had a start problem, hot, cold or in between
- Had a GAMI spread of 0.1GPH (same as my RV-10)
- LOP operation was smooth down to engine stop (same with my RV-10 and it still had mags - new pmags arrive this month!).
- Resetting timing for 100LL or 91UL is simple.
- Moving parts - yep, the fuel pump and a part in the pMag. Don't forget the EFII crank sensor is itself a moving part. Also consider the moving parts needed to keep electrical power going to the EFII system.

I have asked a couple of times for any data to demonstrate that when compared to a balanced traditional fuel injection system and pMags if any EFII system provided more power or higher engine efficiency. I have not received it - other than claims that pMag timing is all wrong. If such data exists, I would love to see it.

So what? If you want EFII fine, go for it. As many people follow these threads please be cautious on how you state facts to support your case. We have so many aftermarket option of late that new builders may think that they must have them all or their plane will fall out of the sky.

Sorry if I stepped on any toes,
Carl
 
While I understand repeating product literature is normally a good thing, I would not want builders to think the objective of cylinder mixture control is to achieve a specific CHT or EGT. This is exactly wrong.

As been discussed on multiple posts, the specific EGT value means little as compared to fuel flow for each cylinder when that cylinder's EGT peaks (GAMI spread). The CHT value, while affected by fuel flow, is best used to verify normal operations, effective engine cooling air, and verify drop when LOP.

If using an EFII and tweaking to achieve a specific EGT or CHT value you will have the cylinders way out of balance.

So other thoughts reflecting on my operation of a balanced AFP injection system and pMags:
- Never had vapor lock
- Never had a start problem, hot, cold or in between
- Had a GAMI spread of 0.1GPH (same as my RV-10)
- LOP operation was smooth down to engine stop (same with my RV-10 and it still had mags - new pmags arrive this month!).
- Resetting timing for 100LL or 91UL is simple.
- Moving parts - yep, the fuel pump and a part in the pMag. Don't forget the EFII crank sensor is itself a moving part. Also consider the moving parts needed to keep electrical power going to the EFII system.

I have asked a couple of times for any data to demonstrate that when compared to a balanced traditional fuel injection system and pMags if any EFII system provided more power or higher engine efficiency. I have not received it - other than claims that pMag timing is all wrong. If such data exists, I would love to see it.

So what? If you want EFII fine, go for it. As many people follow these threads please be cautious on how you state facts to support your case. We have so many aftermarket option of late that new builders may think that they must have them all or their plane will fall out of the sky.

Sorry if I stepped on any toes,
Carl

Hey Carl,

Points and counter points are always appreciated and well taken. Heck, I’m just a shade tree mechanic trying build something that’ll be safe and fun to fly and trying to incorporate a little bit of modern technology along the way. You are correct regarding balancing EGT’s/CHT’s by using fuel flows and equal and balance GAMI being the most important aspect. That’s really what I meant but I guess I just didn’t state it properly. Also, like I said, there’s absolutely nothing wrong with any other type of ignition or fuel injection system and there’s probably hardly any measurable performance difference between any of them....at least nothing that I know that I could measure. LOL!! One thing I am curious about is what you said about the crank sensor. It’s just a Hall effect sensor that senses the magnet position when the imbedded magnets that are in the flywheel passes in front of it....that’s what talkes to the ECU. Can you please elaborate more on what moving parts you’re referring to? Thanks for the good input.

Mark
 
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Mark33;
I questioned (mostly silently) the oil pressure switch shutoff as another mode of failure. However your #4 answer, about this ONLY being active with normal operation of FP #1, and disabled with FP #2. I need to think about it a bit more, but I think I like it.

I am using a "severe service vehicle" fuse and relay panel that uses STDP relays. When I turn the key to "on", the battery contractor energizes and puts 12v to the panel. 87a is used for all normal functions. So no other relay other than the battery contactor needs to function. Switches are provided to switch to turn off FP 1 and 2, ign 1 and 2, and VR 1 and 2. Normal functions are all 87a. Shutting off the primary, and activating the secondary, are on terminal 87.

Carbs vs MFI vs EFI? I won't go in depth as it seems almost religious or political. Between MFI and EFI? The only thing I will say is that if you are using electronic ignition, you are ALREADY using the same primary sensors that the EFI uses. You are just powering a FP and injectors in addition to the coils and spark plugs. A couple of dozen extra wires, and a few electrons. If you are already trusting your warm body to EI, why not go all in and go EFI? Far fewer mechanical moving parts to wear, rebuild, fail.
 
Don't forget the EFII crank sensor is itself a moving part.

The crank sensor is very firmly bolted to the engine case. I can assure you it doesn't move.





Only the magnets embedded in the flywheel move and they can't go anywhere nor is there anything to go wrong with them since they just sit there. No bearings, no rubbing or meshing parts like mags which is why no inspections are required.

Obviously many people see value in EFI or we wouldn't be in business. If your personal preference is mags and a servo with a bunch of moving and wearing parts, that's fine. I always say use what you're comfortable with. Many people do not have the same experience as you with their Bendix style injection and are looking for something to fix their issues.

The topic though is electrical system layouts for EFI, not EFI vs legacy controls.
 
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Yes, please, let's return to topic.

Sorry I drifted from the topic.

Directly responding to electrical distribution, the examples so far discussed in this thread, in my opinion, fall short of what is reasonably possible if the builder wants simplicity, reliably and backup modes when something fails.

For those interested, PM me your email address and I?ll provide some ideas.

Carl
 
Ok, so returning to guidance from an experienced vendor....

As far as I know:
1. Voltage regulator failure leading to over voltage, dual lithium battery installation melt down, electrical system failure.

2. Non standard wiring installation, too small of a circuit breaker used on the injector circuit, injector breaker popped during low level (river following flight), hard landing.
Robert

Thank you. So what can you help us learn?

RV-6: Voltage regulator failure is pretty obvious, based on the pilot report of hot batteries and 15.5V at last check. We've been told EarthX batteries disconnect from charging at around 16.5 volts (but still have an output, however strange that may seem). Let's assume both batteries disconnected at 16.5V, a fair assumption because a meltdown wouldn't happen until failure of the battery management system at 60V or more. How would a battery charging disconnect result in an "electrical system failure" which would kill an EFI/EI? And of course, how might it be prevented?

Airborne Extreme: If I understand correctly, you're saying there was only one circuit breaker for all injectors. There is no standard wiring diagram in the EFII-brand manual. What do you recommend?
 
Back to power architecture!

Glad this is heading back to the OP question!

So I include my latest electrical power architecture scheme. My goal is to be as SIMPLE as possible, with the least number of switches/relays/components. Not a lot of detail here, just concept.

This also stays in line with emergency procedures, as in masters off will not kill the engine. (hopefully we are still flying).

30bnyfs.jpg


This is actually very close to MOD 2 of the original post. I think it has a lot of merit. One bugaboo I have is finding milspec highly rated switches to control the engine bus. Worst case scenario would be around 20amps, would like to be able to de-rate the switch a bit. (and locking would be very preferred). Any ideas?

Now I will sit back and wait to be flogged.....
 
I like Cliff's layout here and I'll have some links for some high current rated Mil Spec switches to post on here tomorrow hopefully.
 
One bugaboo I have is finding milspec highly rated switches to control the engine bus. Worst case scenario would be around 20amps, Any ideas?

I used a switch rated at 20A, double pole and tied the two sides together----In theory this will double the load capacity of the switch.

Worked just fine for me.


All in all your setup looks good. One question......In your diagram is one of the busses carrying essential loads like nav or com equipment? If so, you could tie the two busses together with a diode to provide power from either battery automatically, should one power source take a little nap.
 
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"Oh ****" switch

A good design has no "Oh ****" switch to keep the engine running. Engine electronics need dual power or auto switching.

The airplane is at 200 feet, the departure end just went under the wing, and the engine quits. Right then, nobody has enough spare brainpower to diagnose an electrical problem.

Sorry to state the obvious but one "Oh ****" switch that's always there is the injector ECU select switch if you have dual ECUs. You already have a robust electric power system, both fuel pumps are running, and you located and perhaps also guarded the mixture knob so it won't be accidentally bumped. Flip the injector ECU select switch and check your fuel selector while looking to land. Perfection is a goal we of course will not achieve.
 
Sorry to state the obvious but one "Oh ****" switch that's always there is the injector ECU select switch if you have dual ECUs.

True enough. For now we can only hope some EFI vendor will eventually automate the injector ECU swap.

On topic, we don't want to add more OSS's in the supporting electrical system.
 
True enough. For now we can only hope some EFI vendor will eventually automate the injector ECU swap.

I can only say that after months of work on the CPI-2 to automate switching from one power source to another and the dozens of associated problems and added components, pilot intervention may be a better solution.

Fully 3/4 of the CPI-2 development time has been soaked up trying to do this seemingly simple task. Now if we have to write more code to detect failures of the primary ECU and decide how, if and when we should switch over to the backup, we've added yet more complexity. The benefits become questionable.

I'm not saying we won't go there with the EM-6 since we may be able to apply a lot of the solutions and circuits developed on the CPI-2 but we'll be taking a long hard look at it first.
 
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I'm not saying we won't go there with the EM-6....

In the meantime, it sure would be nice to see a complete wiring diagram for a dual EM-5. This one seems to be missing all the details for injector switching:

http://www.sdsefi.com/dualecu4.pdf

John Bright's notes state that injector switching is different for SDS and EFII installations. Robert doesn't seem to have published a diagram for his version of the EM, or for the System 32. Apparently Mr. Relentless didn't know the secret handshake when he installed the ACE 409 in the SQ12, as Robert says it got parked hard due to "non-standard wiring" (post #70).

So what was (or is) "standard", and how are they different?
 
So I include my latest electrical power architecture scheme. My goal is to be as SIMPLE as possible, with the least number of switches/relays/components. Not a lot of detail here, just concept.

Unfortunately this thread took a 3-page detour. Glad we're getting back to original intent. I'll take a stab at your diagram.

First of all, will you have regulators that you can adjust? I plan to do the B&C ones in mine, even though hopefully the main alt will be off-the-autozone-shelf externally regulated. With these you can reduce the diodes and have overvoltage protection.

I don't think you need two switches to feed the engine bus. I don't feel the need to mitigate the case where two battery contactors fail on a flight. That probability has to be astronomical. So why not feed one of the Engine bus leads right off the contactor?

Here's my design, mostly stolen from Zuldarin. Just a thought experiment so far, but have been thinking about it for some time:

4rXts4c.png
 
For the record:

Although this was originally in reference to automobile racing-----it is often quoted in things aeronautical ........and rightly so.

SimplifyThenAddLightnesColinChapman44x44Final.png

This quote, well, almost, was originally from Ed Heinemann of Douglas Aircraft.
It was said during a prelinary design review for the Douglas A4D. The actual quote was, "simplicate, and add lightness"
 
In the meantime, it sure would be nice to see a complete wiring diagram for a dual EM-5. This one seems to be missing all the details for injector switching:

http://www.sdsefi.com/dualecu4.pdf

John Bright's notes state that injector switching is different for SDS and EFII installations. Robert doesn't seem to have published a diagram for his version of the EM, or for the System 32. Apparently Mr. Relentless didn't know the secret handshake when he installed the ACE 409 in the SQ12, as Robert says it got parked hard due to "non-standard wiring" (post #70).

So what was (or is) "standard", and how are they different?

I didn't draw the details in for the injector relay switching as they are not germane to the basic power/ ground layout which is what this drawing is attempting to easily convey. It would just clutter up the schematic.

Injectors are ground switched through the ECU so only +12V connections are shown. Both ECUs are always active on the 4 cylinder setups, one running each set of 4 spark plugs. The primary ECU normally drives the 4 injectors. The relays just switch injector driving tasks over to backup when you throw the switch. The backup ECU only has essential sensors tied to it- Hall and MAP, no temps or TPS because they're not needed to keep the engine running.

6 cylinder dual ECU setups are quite different from the 4 cylinder ones.

I also don't show all the sensors or charging wiring either for the same reason.

We supply the ECU end of all the wiring completed, built to each customer's length and termination specs. Your task is basically down to connecting the red power and black ground wires provided and crimping the sensor pins once you pull the harnesses through the firewall grommet.

I have no knowledge of how the rebranded dual ECU setups were wired.

With any layout, we feel you must have a way to isolate the essential bus from each battery and alternator because if those go bad in some way you can take down the ECUs.
 
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My goal is to be as SIMPLE as possible, with the least number of switches/relays/components...

This also stays in line with emergency procedures, as in masters off will not kill the engine.

Conceptually excellent.

It would just clutter up the schematic.

The avionics standard is a professional pinout drawing, regardless of who assembles the harness. Why should EFI be different?
 
In response to:

Unitink72:
"First of all, will you have regulators that you can adjust?"

Yes, BandC also.

"I don't think you need two switches to feed the engine bus."
I would defer to the post from Ross at SDS......."With any layout, we feel you must have a way to isolate the essential bus from each battery and alternator because if those go bad in some way you can take down the ECUs."

Mike S:
"I used a switch rated at 20A, double pole and tied the two sides together----In theory this will double the load capacity of the switch."
I did some research on this. It seems that 99.9% of the time, one of the contacts will close first, carrying the full load. Kind of negates doubling them up. So I am looking for a 30A switch. Nevertheless, glad it is working for you, and creative thinking.

"In your diagram is one of the busses carrying essential loads like nav or com equipment? If so, you could tie the two busses together with a diode to provide power from either battery automatically, should one power source take a little nap."
I am considering this, but not sure if I want to tie the two together if not necessary. Diodes can fail either open or closed. Open would then negate it's benefit. And if closed could transfer problem from one bus to another. Just not sure of the benefit/potential risk yet.

I am also not sure about a bus-tie for the same rational. It could transfer overvoltages or issues to the other bus before it is recognized.

I did find this 30A switch. Could not find any locking switch rated at 30A. Any negative opinions? https://www.gamainc.com/product/28a-mtd/

Lastly, thank you for all the responses and help. I could not do this project without all the input.
 
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Conceptually excellent.



The avionics standard is a professional pinout drawing, regardless of who assembles the harness. Why should EFI be different?

If we do a single schematic with every wire and pin shown it would be very hard to follow the basic concepts being discussed in this thread. We prefer to have separate drawings to more clearly illustrate each section. This is simply an overview of the basic power and ground connections, switches and breakers.

Lots of people's eyes glaze over when you have 150 connections shown on one frame.

Cliff's graphic is clearly understood by almost anyone because it's dirt simple. I'll put the question out there though- what are the diodes really doing for you though with the isolation switches on each bus feed, assuming you have only one source at a time connected to the bus, current can only flow one way. I'm thinking they could be ditched too. I've seen diodes fail both shorted and open a number of times over the years.

This thread is starting to drill down to just the essentials required to keep the electronics running with maximum reliability. It's good to see different ideas and evaluate their validity. I just gave this thread 4 stars here. Lots of useful discussion this week.
 
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"I don't think you need two switches to feed the engine bus."
I would defer to the post from Ross at SDS......."With any layout, we feel you must have a way to isolate the essential bus from each battery and alternator because if those go bad in some way you can take down the ECUs."

Mike S:
"I used a switch rated at 20A, double pole and tied the two sides together----In theory this will double the load capacity of the switch."
I did some research on this. It seems that 99.9% of the time, one of the contacts will close first, carrying the full load. Kind of negates doubling them up. So I am looking for a 30A switch. Nevertheless, glad it is working for you, and creative thinking.

"In your diagram is one of the busses carrying essential loads like nav or com equipment? If so, you could tie the two busses together with a diode to provide power from either battery automatically, should one power source take a little nap."
I am considering this, but not sure if I want to tie the two together if not necessary. Diodes can fail either open or closed. Open would then negate it's benefit. And if closed could transfer problem from one bus to another. Just not sure of the benefit/potential risk yet.

I am also not sure about a bus-tie for the same rational. It could transfer overvoltages or issues to the other bus before it is recognized.


Lastly, thank you for all the responses and help. I could not do this project without all the input.

Overvoltage issues should be handled by system(s) independent of bus switching. The B&C regulators should handle that.

I found some of these on ebay:
http://www.elecdirect.com/truck-trailer-parts-connectors/pollak-switches-connectors/pollak-50-30-amp-toggle-switches
The handle is a bit oversized, which you might be able to convince yourself is a good thing (differently shaped switches can help ergonomics).

I'm using one to directly switch my engine bus (auto style efi), and another (different area of the panel) as a bus tie switch. I have the luxury of two identical alternators (alt engine), so I have only engine and avionics buses; no need for load shedding. The avionics bus is switched by a standard master contactor, and starting is handled through the avionics bus.

Charlie
 
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