My -10 has an Electroair ignition on one side and a Slick mag on the other. Is there any benefit to adding a second electronic ignition, specifically a P mag so that a backup electrical bus won't be needed?
Allows starting on "Both", no impulse coupler.
I have dual Plasma III's and it's the easiest hot starting IO360 I have every had! no purge valve etc.
My -10 has an Electroair ignition on one side and a Slick mag on the other. Is there any benefit to adding a second electronic ignition, specifically a P mag so that a backup electrical bus won't be needed?
If you assume 400-500 hours per mag before overhaul or replacement, then the EI has been paid for. And that is NOT counting better fuel consumption.
On a dual mag engine, both mags timed identically, when you turn off either mag, the rpm decreases. Why?
One possible explanation - with a single plug igniting the mixture it takes longer to fully burn the mixture, and some of the mixture burns too late to be (as) useful.
you could be in a situation where if the second ignition was electronic, and hence firing sooner... you might make more useful power.
Of course, there could be alternate explanations... like an electronic ignition makes a 'hotter' spark that makes the mag comparison incorrect.
An interesting test would be - for someone that has dual electronic ignition and has controllable advance on each electronic ignition:
1) climb to 10,000 DA (so at well less than 75% power)
2) presumably the ignitions will be running at around 30 degrees advance
3) record true speed
4) retard ONE of the ignitions to 25 degrees
5) record true speed
my wild hunch - you'll see a couple percent speed degradation.
P-Mag, about $1900 (plus mag gear, plugs, switches, breaker, wiring, etc).
Mag Ovhl, avg $400.
So you can Ovhl the mag about 5 times for the cost of the Pmag install (assuming no labor charge).
The Pmag needs R&R every 100hrs/CI for inspection, and generally returned every few years for SW updating and/or repairs. If you do this yourself great, if a maint shop does it add labor. Pmag service at factory usually runs around $200.
Peak pressure is delayed.
Not sure "useful" is the best term. "...too late to be optimum" is closer.
You're suggesting moving peak pressure closer to TDC would result in more power, which is not necessarily true. Both too early and too late make less power. The problem with too early is it's also very hard on the engine structure.
"Electronic, and hence firing sooner" is likewise not always true. Let's not conflate how the spark is generated (EI) with when it is delivered (timing advance). EI's come in both fixed and variable timing versions, often as options for the same product
"Hotter spark" claims appear to be bad advertising. Is the plasma temperature in the ionized gap actually higher? So far I've not found any such evidence, and I'd be delighted if someone could provide a reference.
The proposal assumes the dual 30 degree timing resulted in optimum point of peak pressure. While close for an angle valve running LOP, it would be too much advance if somewhere in the ROP to peak EGT range. A parallel valve has different timing needs. I've seen dyno charts showing 30 as near optimum for max power with a hot rodded parallel valve, meaning the combustion chamber and port design is not as good. Point is, the result would depend on much more than just a 5 degree timing retard on one ignition. The two largest variables appear to be combustion chamber design and mixture.
P-Mag, about $1900 (plus mag gear, plugs, switches, breaker, wiring, etc).
Mag Ovhl, avg $400.
So you can Ovhl the mag about 5 times for the cost of the Pmag install (assuming no labor charge).
The Pmag needs R&R every 100hrs/CI for inspection, and generally returned every few years for SW updating and/or repairs. If you do this yourself great, if a maint shop does it add labor. Pmag service at factory usually runs around $200.
I have a p-mag and one impulse slick
I’m always worried that the impulse coupler spring will disintegrate so that’s why
I’m looking to add a second EI
Anyone have a Pmag or a Surefly for a 0-200 I’m looking.
Dave
The Pmag needs R&R every 100hrs/CI for inspection
Is the an SB behind this? I didn’t see anything on the emagair site, but I may have missed it.
Interesting that you feel that 30 degrees on stock parallel valve engine, running ROP, at 10,000' DA is too much.
Interesting timing - I was putting along with my io-360 parallel valve at about 140ktas, 8700 DA, FF 6.3 GPH and the EICommander was showing 30.1 degrees advance on my pmags....
30 BTDC is spot on for a parallel valve running ROP at altitude. Photo below from Nigel Speedy's excellent testing.
...
Interesting timing - I was putting along with my io-360 parallel valve at about 140ktas, 8700 DA, FF 6.3 GPH and the EICommander was showing 30.1 degrees advance on my pmags.
If I replace one of my two magnetos (Bendix) with an electronic ignition, which mag (L or R) would I get rid of? And why.....
Too much for an angle valve:
The proposal assumes the dual 30 degree timing resulted in optimum point of peak pressure. While close for an angle valve running LOP, it would be too much advance if somewhere in the ROP to peak EGT range. A parallel valve has different timing needs. I've seen dyno charts showing 30 as near optimum for max power with a hot rodded parallel valve, meaning the combustion chamber and port design is not as good.
30 BTDC is spot on for a parallel valve running ROP at altitude. Photo below from Nigel Speedy's excellent testing.
One timing map does not fit all.
.
I was throttled way back - about 17.5" and about 2150 RPM. I was flying with some guys that like to enjoy the trip and save fuel.WOT? RPM?
30* may be optimal for my PV when ROP up high, but it seems the 10 cowl doesn't allow enough heat shedding in the thinner air to deal with the CHTs that come with optimal advance.
That's interesting. On the 10, my EI does 23* down low and starts to advance around 25". During ROP climbs, once I got to around 8000' my CHTs would start to rise aggressively and by 14,000 I was hitting 425. I put in a knob to manually adjust advance and by dropping the advance closer to 26 or 27 throughout the climb, I was able to keep the temps around 400 or so all the way to 14K'. In LOP cruise, I am seeing around 32* for both ignition's is optimal. I dial it back a couple of degrees when running closer to peak at higher altitudes.