Dan wrote:
First, define significantly
When you can feel it, it is significant 
Though I now have to define “feel” 
“The likely reward is low single-digit percentage increases in speed and efficiency, but the risk is high CHT and potential catastrophic engine damage.”*
according to a very systematic study conducted on IO-360 equipped RV8
https://www.kitplanes.com/the-effects-of-ignition-advance-on-cylinder-head-temperature-speed-and-efficiency/
*Nigel’s RV8 is equipped with 10:1 cylinders therefore detonation margin is “to some extend” reduced, another important point is that from the get go his engine is more efficient than a stock one (1:8,7 compression)
according to a very systematic study conducted on IO-360 equipped RV8
That’s a very good article. I think the benefit of more spark advance at high altitude are worth having (5% more efficiency on top of leaning properly is worth having) but this was the quote that I found particularly interesting: “Efficiency was improved more by simply climbing 4000 feet than optimizing the timing at any given altitude”. This is the difference between cars and planes, although its true that I’ve seen really significant increases in efficiency of motorcycle when operating at e.g. 6000 ft. elevation for a full fuel tank like you can in Colorado or Utah.
You can increase efficiency of smaller engines a lot by increasing the compression ratio of those that were certified on 80/87 fuel but now run on 100LL, for example gaining 10 free horsepower (160 versus 150, 6.6 percent) using IO-320 cylinders on an O-320. Combine that with leaning and more spark advance and it starts to add up for somebody doing long trips at altitude.
On most if not all engines, each magneto’s harness is such that each magneto fires half the upper and lower plugs. Changing that would need a couple of loops or shorter leads and some kind of approval…if not already in the surefly IM.
From here
Dan wrote:
In a nutshell:your bird, and its certification (or lack of), allows you to install EI, and you will
your bird, and its certification, does not allow you to install EI, and you won’t
Very true. Magnetos are truly poor tech compared with EI for several reasons:
Disregarding the first point, and EI will still be better. Better spark will all by itself give better performance/efficiency. Still there are some things to think about. Magnetos have no failure modes that could make things worse. Worst case scenario is both of them stop functioning altogether. The probability of that happening is as good as zero during normal operation/normal maintenance. EI on the other hand, has failure modes that can destroy the engine in seconds, and it is enough that only one of them get that failure mode. In other words, two magnetos is a true redundant system, well thought out. With two independent EI systems, some failure modes will double the probability of (catastrophic) failure. Remove the functionality of dynamically adjusting timing, and it’s definitely a much better system all over. With that functionality (which typically is what is focused on in advertisements), be aware of the nasty failure modes, and adjust engine procedures accordingly. It has caused several accidents, that probably could be prevented if the PIC had better understanding of the systems.
Who cares.
When the price of a Surefly mag is the same as that of a Slick and has a TBO of 2400 hours why would anyone fit a magneto that needs overhauling every 500 hours?
As soon as they have UK approval and the cost to overhaul the mag is 50% of the price of a Surefly. I’ll fit one.
Fixed timing, variable timing I don’t care. Reduced hourly costs well I will have that.
magnetos are 10kV, EI is more like 80kV
I don’t think so, by a long way. I used to design HV power supplies and 10kV would barely jump the plug gap even at MSL, let alone at the cylinder pressure.
When the price of a Surefly mag is the same as that of a Slick and has a TBO of 2400 hours why would anyone fit a magneto that needs overhauling every 500 hours?
The direct replacement is uncertified – for homebuilts only. See here. The D3000 dual magneto is even more convoluted. So we are not there yet…
The are currently working on UK approval but no date yet.
I don’t think so, by a long way. I used to design HV power supplies and 10kV would barely jump the plug gap even at MSL, let alone at the cylinder pressure.
Perhaps it’s a bit higher, but not much. I don’t remember 15kV? The spark plugs are different also. Small gaps, 4 electrodes, to be reasonable sure it fires at all.
