Primarily for general aviation discussion, but other aviation topics are also welcome.
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By AlanB
#1144974
I've just been reading about electronic ignition for Lycomings. It seems that fitting EI can improve fuel consumption by 10-15%, power by 7% and max speed by 2%+.

One method is to replace one magneto with an electronic ignition, which still gives the redundancy of the other magneto in case of EI failure, but most of the articles I have read seem to indicate that the EI are actually more reliable than the old Mags. There is a direct replacement called a P-MAG which has a built in alternator so that if the aeroplane power supply fails, the electronic ignition will keep functioning just fine.

Looks a cost effective upgrade at the next mag overhaul!
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By Merlin83b
#1144979
And to think I just (as in last week) paid for the 500 hour mag overhaul on the Commander. Still, I can't see one mag and one EI working so well in harmony...
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By Paul_Sengupta
#1144985
Is it certified? I've seen uncertified electronic ignition for Lycomings for about 15 years now.
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By Merlin83b
#1144993
Doesn't the "poor" timing of the mag started the combustion at the wrong time, leaving the p-mag to spark too late and in the region behind the flame front? Very happy to be wrong but it seems counter intuitive to me. :scratch:
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By AlanB
#1144999
Isn't it the other way around, the EI fires first and hence the mag firing is redundant unless the EI fails? I am no expert on timing at all :) but I guess this must be the way it works. I believe these devices are certified by the FAA (whether this is for replacement of only 1 Mag though I don't know), and if so is certainly something we'd consider when the next mag overhaul comes up...
By Silvaire
#1145005
The theory is to advance the spark timing when running at highish rpm and lowish manifold pressure... In other words in high altitude cruise configuration. If only one ignition advances, you are more-or-less running on single ignition and it'd be interesting to see how that works with leaned mixture. It'd be fun to experiment.

I can't see the claimed max power increase, or the increase in peak engine efficiency: the standard timing is optimized for that condition, which occurs at low altitude. What it would allow is greater engine efficiency when the engine is running at the less efficient engine operating point that comes with high altitude, which supports higher aerodynamic efficiency.

All bets are off if the engine were turbocharged, because you can maintain MP to higher altitude and wouldn't necessarily want to advance the timing.
By Bill McCarthy
#1145018
A flying buddy has the one mag/ electronic ignition system with fuel injection in his LYC. The electronic ignition spark plugs are standard auto type. LAA permit a/c of course.
By hatzflyer
#1145039
Merlin83b wrote:Doesn't the "poor" timing of the mag started the combustion at the wrong time, leaving the p-mag to spark too late and in the region behind the flame front? Very happy to be wrong but it seems counter intuitive to me. :scratch:


I believe it is usual to start up on the mag and switch it off in flight. There have been large advances ( pun intended ) in ignition systems in the USA through their experimental system (similar to uk permit system ) especially on high performance racing aircraft where mags do not have sufficient advance/retard capability to produce the horse power they require.

The spin off is that well proven systems are know relatively common.

I know that certain people at LAA HQ are very pro electronic ignition because of its huge benefits and reliability
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By Delta Juliet
#1145055
I fitted electronic ignition to my last aircraft and have an application into the LAA to fit it to my current aircraft.

In both cases the system is Lightspeed with the pickup that fits instead of one of the magnetos. I use their car plug adapters and use Iridium plugs.

Starting is much improved as the electronic ignition gives a 1/2" spark which is independent of engine speed. At low speed the system changes the ignition to about 0 degrees advanced (compared to the fixed 20-25 degrees of a magneto). This prevents kickback.

At speed, the ignition is advanced depending on the rpm and manifold pressure. At full power I never noticed much difference, but when leaned and pulled back in the cruise 20"MP/2100rpm there was a big difference in airspeed compared to std ignition. The system advances the spark up to 40 degrees which makes the engine much more efficient.

The advantages are better starting, 10-15 kts extra cruise (135 vs 120kts) and the ability to use Iridium car plugs at £36 a set of 4.
Downside is that it takes a few hours to fit and do the LAA paperwork and it costs about £900. Also it is only for LAA aircraft
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By mick w
#1145071
" At speed, the ignition is advanced depending on the rpm and manifold pressure. At full power I never noticed much difference, but when leaned and pulled back in the cruise 20"MP/2100rpm there was a big difference in airspeed compared to std ignition. The system advances the spark up to 40 degrees which makes the engine much more efficient. "

If a prop is turning at 2100 rpm , it doesn't know what method it is being turned by , and will pull the a/c along at the same speed , whatever it's being driven by , or am I missing something ??. :roll:
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By Delta Juliet
#1145078
Wobbly prop !!


What the man said.

If the engine develops more power then that means more torque at the same rpm.

Therefore the prop has to be coarser to absorb the torque and this means it provides more thrust.

On a fixed pitch prop, you would pull the throttle back to get the same rpm/speed, or get more rpm for the same throttle setting.