The issue is the ability to advance spark timing at lower manifold pressure and highest rpm with the limiting factor being detonation. The standard fixed timing specification is generally set for the worst detonation case which is full throttle at sea level. Then when you climb to lower ambient pressure, the combustion flame front travels slower through the less dense mixture and unless the spark is advanced to account for that, some of the charge goes out the exhaust unburned.
For a high altitude going places aircraft with a non-supercharged engine I'm sure the Lightspeed system works well. For a low altitude operation or turbo that can maintain manifold pressure at altitude, less so.
What external factors do these systems sense?
They don't have knock sensors, I am sure.
Timing is mapped from manifold pressure and rpm, with the effect being not unlike the vacuum advance on an old car's distributor.
I've been considering fitting EI to my Falco for some time but apparently the LAA have their knickers in a twist over the combination of Hartzell props and EI causing some change in harmonic frequency vibration leading to stress failures of the prop blades.
The TCM magneto’s have a TBO of 4 years in service (or 5 years totally including 1 year of storage). The spring needs replacement at that time, the spring is also a weak point, it is smaller in size then for example the spring of Slick magneto, and their is more force on it. When this spring breaks it means it will be out of timing. Not good, certainly on a dual mag.
Just to keep in mind if you have an older TCM magneto.
Welcome to the 1990es… but USD 5’500 O.o ?
Can one not certify an EIS made of auto parts? That’d be 2k US max. Plus QA is bound to be better than some dude making this in a garage.
Also wondering why they use one single coil vs one per spark plug. If one coil packs up you still have the 5 others.
Very nice. I guess I will install it the moment the approval is there.
What happens with the unused portion of the dual mag? They say “one side capped off”, what exactly does that mean? Ideally one would get a single magneto but what’s the approval route for that?
Also wondering why they use one single coil vs one per spark plug
I thought the reason cars went to this was because it minimises the distance the EHT has to travel, which makes the system much less affected by moisture, which is important given the historically notoriously unreliable car electrics.
Also I wonder if they wanted to retain one robustly insulated ignition coil in case somebody is using Champion plugs with their crappy resistors?
What happens with the unused portion of the dual mag? They say “one side capped off”, what exactly does that mean? Ideally one would get a single magneto but what’s the approval route for that?
A good Q. You could route it into the cockpit for some free ozone treatment.
Is a single mag drive point different from the dual mag one? I have no idea. I have a lot of Lyco engine manuals but there are so many combinations…
I fear replacing one magneto by another would be a bit too much for a 337… My impression is that the manufacturer still has a lot of the fine details to sort out. I also believe that the STC does not only have to cover the engine but the airframe as well.
The other certification approach might be to declare it an approved repair of a half broken dual magneto 
