RV-14 Build

Last night and today I worked on wiring the E-Mag electronic ignition system. The wiring was straightforward, I just followed the installation manual and connected the wires to the plugs, then installed the plugs into the magnetos. The time consuming part was routing the wires, and figuring out where to ground the mags. I ended up using the accessory pad studs as the ground, because items nearby, has easy access, and I’m not planning to install a backup alternator at this stage.

I made the ground wires, routed them, then routed the other wires (power, switch, and tach reading). Once I was happy with the wiring, I trimmed the wires, labeled them, and then installed them into the plug.

The E-Mag magneto uses electronics to time the spark, vs. just a static timing as a traditional mag does. The advantage is that the spark timing can be dynamically adjusted based on manifold pressure (which is determined by throttle position and altitude), for a more efficient fuel burn.

The original electronic magnetos needed a backup power supply to continue to operate in an electrical failure scenario. This model has a built in alternator in each magneto, so it will keep running even if all power is lost, and/or manifold pressure is lost. That makes it way simpler to install, and more reliable.

The wiring includes a power wire to power the electronics from the electrical bus, a switch wire to immobilize the unit when activated, and a complimentary tach output which serves as a tech reading for the Garmin system, then there is a ground wire for local ground to the engine block.

The two ignition switches on the panel each have an “off”, “on” and “test” position. They control the left and right magnetos independently. When “off” the switch grounds the “kill” (lt/rt mag sw) wire, which immobilizes the unit. In that condition it is still “awake” and drawing power from the electrical bus, as long as the battery switch is activated. When the ignition switch is set to “on” the kill wire is ungrounded and the ignition will fire. When set to “test”, the power wire is disconnected. The test is to ensure the unit’s internal alternator runs and provides power to the unit. One important note: the internal power has a minimum RPM setting, something around 1100 RPM, below which the internal power will not function. This has several important implications:

• The engine can’t be started without external (to the E-Mag) power.
• The “test” function before flight should be performed above 1100 RPM, ideally at 1700 RPM. The engine RPM will drop if a magneto is in “test” and RPM is below 1100. The engine will quit if both magnetos are in “test” and RPM is below 1100.
• In an emergency if the battery buss is no longer supplying electrical power, and the engine were to quit for any reason, a restart is only possible if the prop is windmilling above 1100 RPM. An example of this condition could be an alternator failure, followed by a fuel starvation event. If switching tanks were to remedy the fuel starvation, the prop needs to be >1100 RPM for the magnetos to fire.

The last few evenings I’ve been working on finalizing the wiring runs in the engine compartment. I looked at a few other aircraft blogs to get a few ideas, and ordered a few supplies. I started by working on the ignition leads and the EGT and CHT probe wiring. I switched out some of the adel clamps I had been using and went with -6 size clamps for all the ignition leads. The leads are slightly loose in this size clamp, but the -5 size is too tight. I wanted to be able to run zip ties through some of the clamps, and it’s helpful to have a little bit of play. The silicone cover on the leads sticks very well to the cushion clamps, so the -6 size seems to work well.

I also used some short (1/4 inch) lengths of rubber tube to create stand-off spacers for the wiring. Running zip ties around the wire bundles and through the tube keeps the wiring together but separated by 1/4 or 1/2 inch or so. Apparently it’s a good idea to have some spacing between the ignition wires and the other wiring runs to minimize interference.

Installing adel clamps is a pain, even with the clamping tool and using safety wire to hold the clamps shut. It’s just slow going.

It’s also slow going trying to visualize the wiring runs, and trying to figure out what wiring will go where. I had to redo work a couple of times, and can already tell I’ll be redoing things in the future. It feels like an iterative process to get everything worked out and squared away.

I’m using a fireproof abrasion protection sleeve on almost all of the wiring. This helps keep the wiring neat and tidy and I hope it will keep it cleaner. The sleeve can be slipped on around the wiring which makes it much easier to install and remove.

Tonight I tackled a few small jobs that had been on the to-do list. I switched out the manifold pressure fluid fitting for one with a restrictor inside, I took some adel clamps off and reinstalled for better wire routing, I safety wired the oil dipstick mount, and I plugged the e-mag ignition cables into the spark plugs.

The manifold pressure fitting I had installed was the Vans component I had originally installed. I later bought the Aircraft Specialty emag install kit, which comes with a 45 degree fitting with a flow restrictor inside. The flow restrictor dampens the fluctuations of air pressure when the engine is running, making for a more accurate manifold pressure reading.

To replace the fitting I first took off the air line, and tried to access the fitting. The baffling makes access a little difficult, so I decided to disconnect the oil return line so I could move that out of the way to gain access. I was then able to access the fitting and remove it. I cleaned up the threads, and then installed the new 45 degree fitting (used loctite 567). Unfortunately I could rotate the 45 degree fitting due to interference with the fluid fitting for the oil return line. I ended up removing that fitting too, installing the MP fitting, cleaning the threads, and then reinstalling the oil return fitting and then the line itself. It was a bit more work than I hoped, but it turned out well and the new setup is much better. The 45 degree fitting also allowed me to reroute the MP line to a more convenient location, out of the way of the oil cooler scat hose.

Safety wiring the oil dipstick mount was hard to reach, but not too bad once I had figured out how to get my hands into the small gap.

I plugged in the ignition lines, and started working on changes to the clamp setup to hold the lines.