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  #11  
Old 10-05-2020, 04:24 PM
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N546RV N546RV is offline
 
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Resurrecting this one for a sanity check, since it's time to place this order. I think I'm settled on the coil locations - one on a mag pad, the other on a top case mount - but the harness lengths are concerning me.

As mentioned before, Ross suggested 7.5' to the crank sensor and 6.5' to the coils. I measure about 4.5' from the ECU location (behind the panel) to the firewall penetration (lower left side).

The big question mark for me is wiring run distances forward of the firewall. In an attempt to estimate require wiring lengths here, I took the overall aircraft length dimension from the plans and subtracted the measured length of the canoe + rudder and the spinner dimension from Whirl Wind; this left me with a ~3' estimate of the cowl length, which I figure works as a starting point for estimating the harness length to the crank. Meanwhile, figuring the run to the back of the engine (for coils) is pretty easy, since the plans call out 13" as the engine mount length.

With that in mind, it seems I probably need something more like 9' and 8' for the harnesses - that leaves 4.5' and 3.5' FWF to route to the crank sensor and coil packs, respectively.

Can anyone comment on the reasonableness of this hand-waving? It's still a bit strange to me that my estimates are significantly more than Ross's suggestions, but maybe most folks are mounting the box closer to the firewall or something?
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  #12  
Old 10-05-2020, 04:59 PM
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rv6ejguy rv6ejguy is offline
 
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Lengths can depend a lot on routing. For instance if you run the Hall cable down the engine spine and then over to one side to penetrate the firewall, that might add 18 inches.

Then if the ECU is mounted on the opposite side, those wires might need to be another 18 inches longer still.

It's best to plan the ECU location and firewall penetration, take a piece of wire and run it along your planned path. Mark and measure that and perhaps add another 6-12 inches.

We usually only terminate one end so you can get wires through the firewall with the smallest hole and be able to tailor your lengths.

We'll happily make your harnesses to any reasonable length you want.

You can coil and cut but can't stretch or add easily if too short.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 445.2 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
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  #13  
Old 10-05-2020, 05:47 PM
Ralph Inkster Ralph Inkster is offline
 
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N546RV
You mentioned your planned firewall penetration would be lower left. It does seem a long wiring run to the Crank Sensor & coils, zig zagging up, down, up & forward. I do hope you are not planning to run the crank sensor wiring below the cylinders (near the starter or alternator cables). Better to run that sensor wiring back above the engine away from any potential electrical interferences.

The Rockets I've installed systems in, although not having the front luggage areas as your plane has, had the firewall penetrations near the top corners or the engine mounts, wiring runs were fairly short because they would follow the top tubes of the mounts to the components or baffling with the crank sensor wiring following the top case joint line (secured with adel clamps) to the crank sensor, again not that long.

The RV SBS models I've installed in had similar wiring runs, all worked out well.

In your case, I'd suggest mounting the ECUs in the well areas below the luggage compartment, either left or right for easy servicing access, resulting in shorter wiring runs to the coils & crank sensor. Again, a bit of extra wire length with excess bundled up is a good thing.
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Last edited by Ralph Inkster : 10-05-2020 at 06:07 PM.
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  #14  
Old 10-05-2020, 10:26 PM
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Foghorn Foghorn is offline
 
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Here is where I mounted my SDS equipment. All the cables I had from Ross fit but I had to run them a few times to get them right. Another foot would have made it much easier. I had to run the crank sensor underneath but on the opposite side from the alternator. All my sensor wires go through the FW on the lower left and all my power wires go through on the right about halfway up the firewall.

You need to check the baffle plans before you mount the coil on top. If you have the fuel block on top then there isnít a lot of room left over, unless the top coil is mount off the centerline. Iím not sure how it mounts on the 4 cylinder engines.

I have two GRT sports and the fastback option which makes getting to the avionics a little easier.



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  #15  
Old 10-05-2020, 10:58 PM
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N546RV N546RV is offline
 
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Quote:
Originally Posted by Ralph Inkster View Post
N546RV
You mentioned your planned firewall penetration would be lower left. It does seem a long wiring run to the Crank Sensor & coils, zig zagging up, down, up & forward. I do hope you are not planning to run the crank sensor wiring below the cylinders (near the starter or alternator cables). Better to run that sensor wiring back above the engine away from any potential electrical interferences.

The Rockets I've installed systems in, although not having the front luggage areas as your plane has, had the firewall penetrations near the top corners or the engine mounts, wiring runs were fairly short because they would follow the top tubes of the mounts to the components or baffling with the crank sensor wiring following the top case joint line (secured with adel clamps) to the crank sensor, again not that long.

The RV SBS models I've installed in had similar wiring runs, all worked out well.

In your case, I'd suggest mounting the ECUs in the well areas below the luggage compartment, either left or right for easy servicing access, resulting in shorter wiring runs to the coils & crank sensor. Again, a bit of extra wire length with excess bundled up is a good thing.
Good food for thought. You've kind of driven to one of the challenges of this process - namely, that FWF routing is something of a mystery to me right now. Without an engine or even mount on hand, I'm having to use a lot of imagination here, and that's made more fun when considering the complexity here. I probably need to do some in-depth studying of FWF stuff, especially the locations of firewall penetrations and mounted components.

Anyway, to more practical discussions..."lower left" is probably not the most accurate description of the currently-intended wiring penetration. One of the design goals here has been to avoid exposed wiring runs in the forward baggage compartment, both for aesthetic and practical reasons (ie potential damage). So the current plan has been to route sensor wiring (EMS stuff, CPI harness, etc) along the left side of the fuselage, and just below the forward baggage shelf.

It occurs to me, though, that I could also route this wiring just inside the deep well in the compartment, which would save a good 3' of harness length. The only real downside I see is that the bundle would need to be secured to a removable part of the aircraft - either the horizontal baggage shelf or the "wall" of the deep well. I imagine that at least the well is rarely removed, so perhaps this is a worthwhile sacrifice.

As for the ECU location, I think my plan of putting it behind the panel is a solid choice for serviceability. Placing it beneath the compartment would require removing the shelf to access it, or else crawling on the floor. With it behind the panel, I'll be able to get to it just by removing the panel center section (or maybe even just an EFIS screen).

This sure is the fun part of the build - those days when all I had to do was follow directions and rivet stuff together were a cakewalk compared to the endless interrelated decisions I'm trying to weigh out these days. But hey, that's where the "education" part of E-AB comes in, and I'm sure it'll contribute to a nice feeling of satisfaction when I'm cruising around in this thing next year.

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  #16  
Old 10-06-2020, 08:02 AM
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Quote:
Originally Posted by N546RV View Post
This sure is the fun part of the build - those days when all I had to do was follow directions and rivet stuff together were a cakewalk compared to the endless interrelated decisions I'm trying to weigh out these days. But hey, that's where the "education" part of E-AB comes in, and I'm sure it'll contribute to a nice feeling of satisfaction when I'm cruising around in this thing next year.

And that's why you see so many completed airframes for sale without engine/avionics. Some folks enjoy the hand-held step by step building part, but have neither the skill nor the curiosity to finish it out. Nothing wrong with that, I suppose, but the FWF and avionics were easily the most fun part of the build for me.
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Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #17  
Old 10-06-2020, 08:13 AM
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I would always try to mount the ECU in a reasonably accessible place as we've had more than a few customers mount them in places you need to be a contortionist to remove once the aircraft is all completed. If your wiring needs to be 9 feet long to reach there, that's no problem.

Many of us learned after the first build to make things more accessible the hard way. As you age, you become less flexible and generally lose your close focus ability. Nothing worse than being upside down, under the panel with your feet up on the seat trying to see something 6 inches away that you can't get your fingers on very easily.

Be sure not to route the Hall sensor cables closer than 1 inch to the plug wires or parallel and close to any other wires with high current/ voltage or pulsing current. Ground the ECUs to separate terminals and don't stack on top of any other grounds.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 445.2 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


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  #18  
Old 10-06-2020, 09:19 AM
Ralph Inkster Ralph Inkster is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
Many of us learned after the first build to make things more accessible the hard way. As you age, you become less flexible and generally lose your close focus ability. Nothing worse than being upside down, under the panel with your feet up on the seat trying to see something 6 inches away that you can't get your fingers on very easily.
Yeh, heís actually describing me, but forgot to mention the addition of more than a couple of pounds In more than a few of my posts I have suggested that folks should design their installations for future ease of servicing! You WILL thank yourself later.
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  #19  
Old 10-06-2020, 05:17 PM
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N546RV N546RV is offline
 
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Quote:
Originally Posted by airguy View Post
And that's why you see so many completed airframes for sale without engine/avionics. Some folks enjoy the hand-held step by step building part, but have neither the skill nor the curiosity to finish it out. Nothing wrong with that, I suppose, but the FWF and avionics were easily the most fun part of the build for me.
It's challenging, but in a fun way. I have to engage my brain a whole lot more and think 439 steps ahead, but there's the motivational aspect because I'm doing the stuff that's turning an aluminum canoe into a machine.

Turning these kinds of abstract problems over and over in my head until solutions fall out is the exact thing that I enjoy the most about my day job. The difference is that when I make a misstep in software it's a whole lot easier and cheaper to fix than if I order the wrong part. It doesn't change the fun problem-solving aspect, but does make me care more about trying to think through everything.

I appreciate all the input, sanity checks are good to help me pick out the point in time when I can stop thinking and start doing.
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  #20  
Old 10-06-2020, 06:00 PM
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Yup - heaven forbid it ever happens, but if I ever take a birdstrike and bust the windshield and I'm forced to tear into the front structure anyway, I'm going to unrivet the top forward skin and rape out my entire panel-forward area and reinstall it the way I want it to be now.
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Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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