Powerplant: Switched to dual SureFly electronic ignition.

My magnetos were approaching 500 hours so it was time to consider whether I wanted to overhaul them or try something different. My ignition harnesses were also getting ratty with fractures in the shield (necessitating crimping a new connector on one cable due to excessive radio interference).  In this post, you can read about my changeover to automotive harnesses and plugs.

I decided to go with electronic ignition, opting for the SureFly magnetos rather than E-MAG's products.  Back in August, I swapped out the left magneto for a SureFly to see how things would go, with the intent to later switch out the right magneto too.  Update 12-Dec-25: I had serious kickback events with the SureFlys.  Please read the bottom of this post to learn more.

The SureFly can be set for constant or variable timing.  Using variable timing requires a hose connection for manifold pressure.  There are little DIP switches that let you select the timing options.  I chose 22° variable timing (the engine is placarded 20° ).  An LED on the SureFly blinks using Morse Code to anunciate and verify its timing selection.  Update 23-Jul-25:  I spoke to a SureFly rep at OSH and was informed that all of their mags retard timing at < 400 RPM.

The gear from the original Slick magneto is reused.  Removing the gear from the original magneto is straightforward after removing its cotter pin then placing the gear in a vise.  Getting the new cotter pin on the SureFly is a challenge.  I found that preforming the pin prior to insertion is the way to go.

Here's the left SureFly in place after properly aligning it to TDC of the engine.  Not shown in the picture is the MAP pressure hose that was later routed to the pressure port at cylinder 4.  For that port, I used a barbed hose 1/8" hose to 1/4" NPT male fitting made of 303/304 stainless steel (McMaster Carr link).

Flying with this setup, I noticed no difference in how the airplane started (cold or hot) or how the engine ran.  My GRT EIS (engine information system) could not resolve the tachometer signal from the SureFly.  I tried using a coupling capacitor to no avail, so it was clear I would need to use SureFly's very expensive TACH2 signal conditioner.  Until then, only my right magneto was providing RPM info (e.g., when I did a mag check, the EIS would show 0 RPM when the right mag was grounded out).  So I used my TruTach II tachometer during mag checks until I later installed the TACH2 conditioner (shown later below).

After flying 15 hours with this setup, my condition inspection was coming up so it was time to replace the right Slick magneto with a SureFly also.  I needed to consider a backup power option (outlined here) for one of the magnetos since it's just good sense to have backup power available to at least one of the magnetos when one has a fully electronic ignition, even though I have dual alternators.

Shown below is from the installation of the right magneto.  It turns out that SureFly programs all their magnetos with retarded timing so you can fire both magnetos at start.  This required removing a jumper on my ACS A-510-2 ignition switch to ensure that the right magneto is not grounded out at start.  I used the MAP port from cylinder 1 with the same fitting described as for the left magneto.

Hot starts now require a different approach with the SureFlys.  Before, I would start with the mixture full lean, crank the engine whilst slowly advancing the mixture, stop cranking when the engine catches, push mixture in a little bit more then turn on the bust pump.  That sequence never works now.  To hot start with the SureFlys, I keep the mixture at full lean and crank the engine for just a few seconds then release.  The engine will slowly start using the momentum of a cylinder occasionally firing.  When it seems like the engine has started, I advance the mixture.  Fuel pump is not usually needed unless firing seems inconsistent.

Here's the very expensive TACH2 signal conditioner that allows my GRT EIS to read the tach signal from the SureFlys. I was curious why it was so expensive, so I opened it up to see its guts.  It remains unclear to me why its cost is so high.  I installed this on what little space remained on my subpanel.

Next up was designing the backup battery setup.  I put that in a separate post which you can find here.

Update 12-Dec-25: I had serious kickback events with the SureFlys.  Read on to learn more.

 

Kickback Problem and Solution 

 

Background info to help situate the issue:

• Cold starts are like a dream.  No problem.  Starts in maybe one turn of a blade.
• Hot starts, especially when it's also hot outside, can cause kickback.
• When the starter is engaged, shortly afterwards the prop just stops turning in place (due to mistimed ignition), completely overriding the starter.   Or the prop is just sent spinning in the reverse direction (!) due to  mistimed ignition.  
• Many times, a hot engine simply won't start when cranking (key in "start" position).  
• You have to release the key from "start" (i.e., disengage the starter) and go to "both" and hope the momentum of the prop carries through to get the SureFly to fire, ultimately starting the engine. 

I had a couple of very long phone conversations with SureFly to try to understand the issue.  I am grateful for the time they spent with me.  Together we came up with some possibilities for my kickback problem.  However, it wasn't clear to me how these suggestions address that the issue happens only during hot starts.  When I pressed them on that, they were frustratingly well-trained to keep circling back to the first two issues I outline below.

1. They say that many start switches (ACS A-510-2 in my case) have intermittent ground faults in the "start" position.  That won't cause an issue with classic magnetos (like the Slicks I had) because those mags still generate spark as the mag is moving.  Just so long as the intermittent grounding doesn't occur at the firing point, a classic mag still fires.  But with a SureFly, as soon as you ground the thing, even intermittently, it basically shuts off and releases the energy (to ground I presume) it had "accumulated" for the spark.  When the SureFly is subsequently ungrounded, it takes a fraction of a second to come online so it may not fire before the next intermittent grounding happens.  Thus, it may never fire until the key is moved from "start" to "both".
• I used a high sampling rate oscilloscope to verify that my start switch was not grounding the magnetos during start.  I rapidly switched between "start" and "both" with the mags off.  I tried this when the switch was "cold" and after heating it.  The ACS switch was not the cause of  kickback.
2. They said that even though I followed the correct procedure to find engine TDC (remove T1 plug, cycle engine to find compression stroke, align ring gear marker with case seam), the ring gear mark can be off somewhat or you can suffer from parallax when aligning the mark to the case seam.  They highly recommend using the pointer that Lycoming sells to remove any parallax.  I bought that pointer and it didn't fit my engine.
• Instead, I used a fixed micrometer on the cylinder 1 piston to verify TDC.  This verified that my SureFly magnetos had been perfectly aligned to TDC.  Timing misalignment was not the cause of kickback.
3. Try starting with the right mag only and see if there's a difference.
• I rewired my ACS switch to do this.  No change in kickback behavior.  
• It's worth noting that my right mag gets its power from the main battery at start and the left mag gets its power from whichever battery has the highest voltage (usually the backup battery).  So this test also isolated the batteries as a source of the kickback issue.  Interestingly, the rep said the SureFly functions even down to 5 Volts.
• Starting with both mags still causes kickback. 
• Thus, the kickback was not due to a specific mag or my batteries. 
4. Finally, they also said that after 4 or 5 seconds of cranking, the SureFly won't generate spark.  It's programmed to stop after that duration of cranking.  So if it doesn't start in 4 to 5 seconds, stop cranking and try again.  He mentioned this since I said I crank for a max of 10 seconds (per the starter's labeling).  This is not published anywhere, probably in support of their "drop-in replacement" messaging.

I suggested to the rep that the SureFlys have inconsistent timing when heat-soaked.  He said that they tested them to something like 500 °F (!) and they kept going.  In fact, he said they started a fire in the test facility during that testing.  He said I could send my mags in to them for heat-soak testing.  I declined that offer.

Ultimately, during my condition inspection last month, I opted to re-time the mags to prevent kickback.  I've aligned them to 4.83° ATDC (two teeth on the 149-tooth ring gear) and set them for 26° BDTC variable timing.  Thus, at start both mags will fire when the piston is receding so that kickback should never occur.  In flight, they will fire at 21.2° BDTC (the engine is placarded at 20° even though it came from the factory set at 25°) and when they switch to variable timing mode, I will get at most 33.2° of advance rather than 38°.

Thus far, all hot starts have been trouble-free and without kickback.  I will probably never understand why the mags caused kickback only during hot starts and seems likely that SureFly won't know either.   

Champion has a new magneto that requires no external power and operates down to 100 RPM.  This might be something form me to consider later.