Electronic ignition and leaning
Walter Atkinson said:
Gentlemen:
1) I only know of one pilot who has claimed to have heard detonation from the cockpit.
2) The trouble-shooting guides of JPI, EI, and GEM notwithstanding, detonation does not result in EGTs going down while CHT's go up. If EGT's move at all, it is so little that you wouldn't notice it.
3) Detonation, contrary to many years of incorrect assumption, is not very damaging to an engine as long as it is not allowed to progress to the point that it becomes pre-ignition. Keep pre-ignition out of the picture and the engine seems to survive detonation pretty well--hangar-flying expert opinions not withstanding. We have watched many, many hours of light and medium and even a little bit of heavy detonation and have even had the engine torn down by third parties to assess any damage. NONE.
4) Leaning by Target EGT is clearly the optimal way to go. Some engines and fuel set-ups do this for you automatically. Others require more pilot input. The result is the same.
5) Leaning an engine set WOT, does, indeed, override the fuel enrichment in the design. There is no need to bring the throttle back out of the auto-enrichment range.
6) Altering timing without a full ICP map of the effects is a risky business. Detonation margin erodes quickly. It could quickly result in detonation and/or pre-ignition. So far, I am unaware that any of the electronic ignition companies have actually done these tests. I only know of one place in the US where these tests could be run and it hasn't been done there. If you are using altered timing maps, you are a TEST PILOT. Be aware, significant risks are there. To each his own. I have SEEN these effects with my own eyes on a live running engine and I am impressed with the negative effects.
Nothing substitutes for real, live engine testing on a very advanced, computerized test stand where you can WATCH this for yourself.
If I can answer any other specific questions on this subject, feel free to let me know.
Walter Atkinson Advanced Pilot Seminars
To summarize points 1) and 2), you can't tell if you are detonating useless you have hearing like a dog. I agree, EGT and CHT is not a reliable indicator of detonation and its too late for pre-ignition. Thanks for the input.
Item 3), I don't know what light, medium detonation means? Regardless I can't recognize detonation, therefore I follow procedures to prevent it, like not leaning above 75% power. How can I use the concept that detonation is not that bad? Detonation, even "light" can crack plugs, which will than lead to pre-iginiton. Before I disregard the manufacture and accept another experts opinion, I would like more data than "we have watched IT for many hours". What engine? Tell me how do I know I'm detonating again? Your comments are vague and nonspecific, sorry. I guess we can agree to disagree.
Item 4) Agree 100%. Lycoming drivers find EGT drop is small in climb. Therefore the Target EGT method has less benefit. Carbs and fuel injection used on Lycs do lean with out pilot action during climb, unlike the fuel injection on most Contenentals, which are pure mechanical units working on RPM and throttle position only. The AvWeb article was written for the TCM (Continental) not the Lyc. Leaning below 5,000 feet or above 75% pwr is not a good idea IMHO. Each to his own. Above 5,000 or below 75% target EGT away. I talked to Lycoming, they say don't do it, and they do have data to back it up, that you don't have. What expert to believe?
Item 5), I don't know what you mean? You got it backwards. Leaving the throttle WOT overides the auto lean on MA carbs used on Lycs. Not sure why you want to change the procedures for carburated Lycs. Yes you can override the bleed air valve (economizer) with wide OPEN throttle and lean in climb using the target EGT. Why and to what advantage I'm not sure. Clearly a big advantage for a TCM engine. Are we changing for change sake or trying to fly our Lycs like TCM engines? AFM?s for Lyc powered aircraft recommend a slight power reduction after takeoff for climb for a reason, not arbitrary.
Item 6) You have alluded to this "computerized test stand" data showing electronic ignition is dangerous!
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I speak for many, please tell us more. I know you're proud of the "ery advanced, computerized " ?
GAMI?s Carl Goulet Memorial Engine Test Facility?. Don't scare us and give no data. What ignition curve and what engine? Why keep it secret.
Personal EI experience has been positive. Engine runs smoother, making more power with better spacific fuel consumption. I never heard of any EI induced detonation or engine damage. I think the experience of 1000's of pilots with EI speaks well comparied to your one test?
True experimental EI systems may not be "Dyno-ed", but the LASAR has. LASAR worked direct with Lycoming and of course the FAA in their certification efforts. Lyc has advanced computerized test equip BTW.
EI offered on the market are safe, here's why:
My references are:
Unison engineering and LASAR ignition,
Klaus Savier at Light Speed Engineering,
Jeff Rose at ElectoAir when he was running the show.
Aerosance/Lyc engineering certified & experimental FADEC systems.
LASAR - used "computerized test stand" data from Lycoming no one else is privy to, including you. They feel their system provides safe timing adv. Considering it has been on the market for +5 years, with many units flown countless hours, what is the problem? LASAR is a FAA certified system. I assume Lycoming, Unison and the FAA know something about doing this safely.
Klaus @ LightSpeed - has sold his Plasma EI units for over 10 years successfully with no detonation or engine damage.
Jeff Rose's ElectroAir - I talked to him and he's very smart and convinced me that the method he used in the timing curve is safe. Again apparently no one has damaged an engine.
ElectroAir's fixed RPM/MAP curve is below.
Here is the ElectroAir timing formula and curves:
EIS Spark Advance (Timing) = Installed Adv (0) + RPM Advance + Vacuum Advance
Ideal or perfect? No. Safe conservative timing curve scheme? Yes. Way better than a fixed 25 degrees? Yes (NOTE: Vac advance starts at 24", which is about 5,000 feet, hummm. LASAR starts at 27"!)
Aerosance - Their FADEC includes electronic ignition and electronic port fuel injection. They don't use combustion pressure. What timing advance curve do they use? It's certified. It's even certified on your beloved TCM engines which are now available with Aerosance FADEC. It's a Lyc option for a little over $7,000. What is the "PRISM" going to cost?
Conclusion all the EI: Light speed, ElectroAir, and E-mag have a conservative scheme to advance timing that's less aggressive than the certified and tested LASAR, e.g., LASAR starts adv over 25 deg at 27" MAP where ElectroAir starts at 24". They are all extensively field proven.
Walter I know your GAMI buddies are working on the "PRISM electronic ignition" which will utilize "ICP map" combustion pressure input to advance timing. Knowing combustion pressure is SUPER, but making a practical, reliable, production inflight instrument to measure combustion pressure will be a challenge. Good luck; keep us posted. RPM/MAP has worked exceedingly well. (Note: ICP - Integrated Circuit Piezoelectric, tm name of PCB Piezotrinics, Inc.)
Walter, tell us more specifics of the data showing EI adv is not safe?
You put this BIG CLOUD over our experimental EI, with out stating the data to support your claim. Why worry folks if it does not apply. If there's a problem, please tell us what EI? What timing curve? Was it tested leaned?