Electronic Ignition is Dangerous? may be
Walter Atkinson said:
someone would ask these guys what their ICP curves look like as the timing map is changed. So far, I am unaware of any of them who have that data- Personally, I would not put ANY ignition system on an airplane without first having seen that data. Walter
Good, point. You probably are right they don't have the ICP data. Have you done any test on EI? EI makers don't publish their MAP timing curves because they're proprietary I guess.
I asked questions of at least three EI manufactures and read all their literature. From service it's ironic the only certified EI, LASAR, seems to give operational issues for pilots with the highest CHT's.
In general timing remains fixed at 25 degrees until the power is 75% or less. Than the max advance for all of them is around or approx 40-42 degrees. The Lightspeed Plasma system has a cockpit timing adv display option, so it's not a secret. Any one know what E-mag, LS plasma or other timing curves are?
It would be wounderful to get data like ICP you have available with your test cell. Any chance you'll do testing with differnt small 320/360 Lycs and EI?
WHY is advanced timing is goodness? My understanding is at low power and lean mixtures the flame front slows down. If the ignition stays retarded it's too late. Rich mixtures burn fast so retarded timing is best, but too much advance at high power can cause pre ignition and detonation. Both can cause serious damage as we know.
Walter you are implying there's some danger with timing advance? I agree, but my understanding is like LOP, if the power is low than T-adv is safe within reason. Obviously if timing is totally wacky it can cause backfire, power loss and engine damage. Is 42 degrees max adv not modest? Walter, RV6ejguy, Bob, Jconard what you-all think?
Jconard said:
"I know I'll get flamed here, but a slight hesitation in an airplane would be considered a deal killer in a race car. This is where the advantage in variable mapped fuel and ignition systems pay off in auto applications, and are where the "technological advances" pay off <snip> electronic ignition, which can operate well at altitude, there is NO performance advantage. Many people simply have an emotional response, based on the belief that EI / FI MUST be better than mag/carbs."
You're right on, but "Better" needs context. My O-360-A1A, I enjoy a simple fuel system and very good performance. The FI vs. Carb issue is complicated with things like carb ice, aerobatics and possible LOP operations, but my carb is not prone to ice (vfr), I do all the acro I want and I'll give the LOP thing a try.
However with EI, I don't buy the NO performance advantage comment. I plan a dual EI plasma system. With 4-5% or better efficency, smoother operation it's a valid replacement to the venerable magneto. (Data from cafe foundation org report on EI). However all you fly is local down low, the EI advantage is smaller. If you climb to 10,500 ft and cruise mostly, than EI shines. So I partially agree. If you are starting from scratch than at least one EI seems reasonable. If you already have two good magnetos, than staying with them might make more economic sense.
BOBM said:
(corrected) I beg to disagree. If FI were necessary for LOP, then how did Lindberg get to Paris, the P-38 boys fly 1350 miles to get Yamamato........ Max Conrad set all those distance records in little Indians in the 50' & early 60's?
Bob you are right, but I would point out not all Carb engines are the same. A big low compression radial is not the same as a small Lyc. Engines are engines, true, but when one jug of a BIG rotating mass engine stumbles a little it's not as noticeable. Also there is less crank rotation till the next one fires. On a little 4 banger when one starts to stumble (uneven power pulse) it gets unpleasant waiting 90 degree crank rotation for another shot.[/U]