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  #271  
Old 02-17-2020, 07:58 AM
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DanH DanH is offline
 
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Two photos to clarify coil wiring, 4 cyl of course, 6 cyl conceptually similar.

These are coil packs, two coils packaged together. Each coil has two spark plug towers, as each coil fires two cylinders at the same time, every time those cylinders approach TDC.

Early coil. Uses a plastic retainer for positive retention of the plug lead cap in the tower. Bottom isn't flat, so it must be mounted on standoffs. This fancy blue one is aftermarket. When viewing the bottom, the individual coils are really obvious.



Late style coil, also familiar to P-mag users. Taller towers, flat cast epoxy bottom. Here the individual coils are obvious from the top.



The pinout is logical, and the same for both types. Power is supplied to the center pin. The EDIS module's coil driver circuits switch coil ground, on to build a magnetic field, off to cause a spark. Each coil is controlled by the pin closest to it, with EDIS pin 10 being (in our engines) cyls 1 and 2, an opposing pair.

These are Ford OEM or aftermarket coils specifically intended for EDIS, but I'm pretty sure the EDIS module will fire any similar waste spark coil without an internal coil driver. The module incorporates coil current limiting. I happened to do some measuring recently. Early style coils appeared to be fully saturated, and spark duration with new IKH27 plugs stock-gapped at 0.8mm was 22~24 degrees in the cruise RPM range.
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Last edited by DanH : 02-17-2020 at 10:10 AM.
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  #272  
Old 02-18-2020, 05:07 AM
WingsOnWheels WingsOnWheels is online now
 
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Dan,

That is an excellent post on the coils, thanks. In general, the megajolt manual is a little light in this area.

I ended up using the late style coil. The early style would be a better fit for my installation, but I was having trouble finding boots and retainers to match the MSD superconductor wires.

For the late model coils, boots and terminals sold for LS1 coils work perfectly. I was concerned about retention, but the boots hold onto the towers aggressively.
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  #273  
Old 02-24-2020, 08:23 AM
WingsOnWheels WingsOnWheels is online now
 
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My EDIS system is working very well so far. I have about 2 hrs of flight time (plus about an hour of ground testing). I haven't been able to do full performance testing yet, focused on functional checkout at this point. The most obvious observation is much easier cold and hot starting. That is a huge difference. ~40f OAT and starts in 1-2 blades at most. Startup is also very smooth as Dan noted earlier in this thread. Since I am still running the mag on the left side, there is no advantage gained by the reduced advance during idle.

At first look, switching from flat to modified curve in cruise buys about 30rpm (fixed pitch). I now have to be careful since I can exceed 2750 rpm at higher altitudes than before. I think my Catto is a little underpitched for max speed.

More testing to come. I am already working on the hardware for a second system, but need to lay out a solid electrical plan before going to two EIs.
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Last edited by WingsOnWheels : 03-14-2020 at 11:58 AM.
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