I have looked through a couple of the threads on the Electroair electronic ignition system and I thought I would offer up a description of the system, a discussion on how the ignition works, some of our engineering thought processes and then field questions as best I can. This may help clarify some of the things that have been discussed so far. I will try my best to reply as quickly as practical, so if I?m not right back to you, please be patient. Here we go?
The Electroair electronic ignition system (EIS) is a single magneto replacement. In other words, one mag gets replaced with the EIS, one mag stays on the engine. In general terms, it doesn?t matter which magneto gets replaced (we can talk about which mag to replace later).
There are a number of reasons why we didn?t pursue replacing both magnetos: 1. Our data shows that the benefit from a second electronic ignition system is marginal. Given the flight envelopes that GA aircraft typically operate in, the substantial benefit of having electronic ignition comes with the first electronic ignition system; 2. By having two dissimilar ignitions installed (one EIS and one mag), there will never be the same failure mode for both systems ? safety is improved; 3. Approving two EIS systems meant that a second alternator was also going to have to be approved (if it was not on the aircraft already) ? most legacy aircraft do not have an easy way to have a second alternator installed (certification of a single system was easier with the FAA too); and 4. When looking at the cost-benefit analysis, it is much easier to demonstrate a pay-back to the investment of one EIS versus two.
The Electroair electronic ignition system differs from a magneto in two principle ways:
First: The quality and duration of the spark. A magneto will put out about 6-8,000 volts during start (~12,000 volts during normal operation) and has a spark-duration of five degrees of crank rotation. The EIS will produce about 70,000 volts (during start and normal operation) with a spark-duration of twenty degrees of crank rotation. The hotter, longer duration spark lets us operate with wider-gapped spark plugs, ensure a much better ignition of a given fuel/air mixture, and improve starting with ?corrupt? fuel/air mixtures (hot starts). Also, since the EIS is a ?distributor-less? ignition, the quality and duration of the spark remains very good throughout most flight regimes (high altitude, etc.). Distributors, points, and other parts in magnetos all reduce the amount of energy that can be made available at the spark plug.
Second: Variable timing vs. Fixed Timing. Remember, the goal of any ignition system is to start the combustion event so that peak pressure occurs between 10-17 degrees after Top Dead Center (TDC). (Note: Lots of papers discuss particular angles, etc.; it is generally accepted that the optimal range for peak pressure is 10-17 degrees ATDC). The magneto has fixed timing and cannot adjust for altitude adjustments (changes in MAP). The EIS has a MAP sensor and can adjust the ignition timing for the changes in the fuel/air mixture that occur with altitude changes. By adjusting the ignition timing for the reduction in MAP that occurs with altitude (and typical cruise settings), the combustion event can be started so peak pressure from combustion in the cylinder is maintained between 10-17 degrees ATDC.
The Electroair EIS is made up of several components. The Controller and MAP Sensor are installed on the cool side of the firewall. The coil pack is installed on the engine side of the firewall (for tightly packed installations, other installation locations are being investigated). High energy spark plug wires are supplied that are fabricated during the installation. There is a pre-fabricated wiring harness for the components. And finally, there is a trigger mechanism that comes with the kit (depends on the engine). The installer will have to supply a switch, circuit protection and basic hardware needed to complete the installation.
The benefits of an electronic ignition system have been well documented in the experimental world for a number of years. Improved fuel economy, smoother running engine, better performing engine, and better starting are all things we expect operators will experience with the Electroair system. The installations that are being completed in the certified world are showing results consistent with what has been experienced by their experimental counter-parts. The Electroair website is updated regularly with customer reports.
We are asked on a regular basis what a typical installation time should be expected for this system. I do not have a good answer. Installation times are really dependent on the aircraft and how ready it is receive new components, the installers? ability (first time installers are going to take longer than installers who have installed a few), a good installation plan, and common sense. We have had installation times reported back to us that are as short as six hours (Super Cub) to upwards of twenty hours and longer (some of those reports, it was found out later, included updates to the aircraft that were not required for installing the system). I have given estimates before about installation times. My estimates, however, are just that, an estimate. Every airplane is different! My STRONG recommendation is to have good communication with your technician and work out an installation plan that both of you are comfortable executing. I would allow for two-three days of down time to be on the safe side. The EIS is NOT a complicated system, but requires the installer to think of it more like avionics. We are happy to answer questions (and encourage questions) before and during installation.
I hope this helps answer several questions and clarify some points that have been discussed in other threads. I?ll be happy to answer follow-up questions as best I can. I look forward to the discussion.
Thanks?
Mike
Electroair
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Michael Kobylik