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Electronic ignition

Dan, when you get your multiple map capability up and running will you contribute some data as well? Would be nice to see how the hot rod angle valve with its faster burn combustion chamber responds.

Been up and running for years now. However, don't wait on me for a full blown timing survey. I've already got more things going than I can says grace over.
 
I chose Lightspeed Plasma III?s mainly for three reasons:

1- Over-rev protection(not a issue for fixed pitch). I?m personally aware of three runaway prop events.
...snip

Otis

This is a nice sounding marketing feature, but I suspect it is of limited usefulness in cases of lost prop-control oil pressure at high air speeds. It might help limit the over-rev but likely the aerodynamic forces on the prop at fine pitch will still over-rev the engine, kind of like shifting a manual transmission automobile into first gear at 70 mph.

Skylor
 
Flywheel triggers have their own failure modes that can be nasty. I have had inflight failures with a flywheel system...Yikes!


V

What are the failure modes for flywheel triggers? Do they result in something beyond that system becoming inoperative?
 
What are the failure modes for flywheel triggers? Do they result in something beyond that system becoming inoperative?

Two hree that I can recall reading about:
1. The trigger magnet comes off resulting in no more spark
2. The alternator belt snaps, ripping the trigger wires off, resulting in no spark.
3. One trigger boad equals one point of failure.
 
Two hree that I can recall reading about:
1. The trigger magnet comes off resulting in no more spark
2. The alternator belt snaps, ripping the trigger wires off, resulting in no spark.
3. One trigger boad equals one point of failure.

Maybe you're thinking about some other brands.

1. On SDS, the magnets are in the INSIDE of the flywheel, mounted flush, stuck magnetically to two ferrous set screws threaded into the flywheel. Also epoxied in the bore and held in with 20Gs worth of rotational force when operating. Never been a case of them falling out on a Lycoming engine.

2. Mags or mag drive type EIs are driven by many gears, supported by bearings which have been known to fail from reports right here on VAF. Often catastrophic as the gears swallow the pieces. Crank mounted triggers have way less moving parts and therefore less to fail. We have provision to armor the cables. The mount is strong enough to lift the whole airplane up by. No way the belt will take out the cables in this case.

3. Dual redundant sensors, keeps at least one set of plugs firing. Never had a Hall sensor fail yet electronically on SDS-millions of hours collectively on nearly 10,000 systems over 20+ years.

Crank triggered ignition are used by all automotive OEMs today and have been by most for over 20 years. Why? They are more accurate, less expensive and more reliable than gear driven, add-on devices.
 
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So I'm not so sure the -9 wing outperforms the RV-8 at altitude. But needless to say, these RV's (short and long winged ;)) are pretty good airplanes!

Agreed, if anything, these numbers are even better than Bill's. There's many other variables but the short wing and injection doesn't seem to be hurting anything here. Thanks for the post and screenshots.

For reference, Dave Anders observed these numbers at 17,500 with dual LS ignitions and SDS EFI albeit with higher CR pistons and lots of other engine and aero tweaks:

158 KTAS 4.8 GPH
171 KTAS 5.2 GPH
181 KTAS 5.7 GPH

At 18,000 145 KTAS 3.7 GPH

Anyone care to post their numbers with mags?
 
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Not sure there is any relevance with a -10 but hey.... :)

FL170 KTAS170 DA19230' 15.7"/2520RPM 10.7GPH and about 75-100dF ROP, and this was a few years ago, when LOP it was around 8.7-9.0 GPH (I think) but the speed and elevator drag started to become an issue so ROP we were. No doubt the use of an EI at this height would have helped with lean mixtures.

FL130 KTAS159 DA14271 18.3"/2480RPM 9.5GPH

10'000' KTAS160 DA10555 21"/2390RPM 10.5GPH

FL140 KTAS160 DA15287 17.7"/2440RPM 9.2GPH

FL150 KTAS145 DA16583 16.9"/2410RPM 8.2GPH and this photo was taken fooling around to see how lean it would go, but the speed rolled off so far and did not suit my purposes. Any leaner she would have stopped. an EI would have helped a bit. Rest of the trip was at about 9.2 GPH and 156-8 KTAS.

9000' 164-166KTAS DA11172 21.5"/2410RPM 10.5-10.6 GPH and this is a more normal flight with normal loads etc.
 
Numbers with mags

My numbers with mags aren't as good as Dave Anders, but whose are? But my Superior io360 Catto 3 blade equipped RV8 does pretty well at altitude. How about 178 ktas at 15,950 da burning 7.77 gph. Or just under 12,000 da at 158 ktas burning 5.85 gph. Both of these are rich of peak.
I have posted screen shots in the past, but not having much success at it or I would put them up here.
 
All good numbers. RVs with Lycosaurus' do pretty well for fuel economy, short, constant chord wing and all.
 
This is a nice sounding marketing feature, but I suspect it is of limited usefulness in cases of lost prop-control oil pressure at high air speeds. It might help limit the over-rev but likely the aerodynamic forces on the prop at fine pitch will still over-rev the engine, kind of like shifting a manual transmission automobile into first gear at 70 mph.

Skylor

Actually, when you shut down the ignition completely on a 200HP Lyc. operating at or near WOT, it is instantly transformed from a huge power generator(the real driving force behind runaway props) to a large power absorber, and aircraft propellers are not very efficient windmills. With a low inertia aircraft like an RV, I think you would need to be going very fast at a steep down angle for the aerodynamic forces to further increase RPM levels sufficient to do harm. The rev-limiter should give the pilot time to retard the throttle and prevent a second cycle. I don’t think the downshift analogy you cite really holds up here, but aerodynamic drive is an inertia related factor to consider.
 
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FYI -

1. P-mags also have a rev limiter, which is adjustable.
2. Software is an advantage as it allows the ignition to be tuned for your application.
3. Flywheel triggers can fail as mentioned in the article I have proved the link to below, even though it is not a Lycoming engine, it is worth reading. Also there was a report a few years back of someone who had a dual LS installation. His alternator belt snapped and took out both trigger wires. The P-mag installation is still the simplest of all the EI's I have seen.

1- didn’t know that-thanks! With the lightspeeds you can specify the cut-out and cut-in revs, which then remain fixed.
2-Granted, but I don’t like software in critical components. An optional limited manual advance selector does permit some in flight customization with the Lightspeeds.
3- You do have to be very careful about routing sensor cables, especially to reduce the liklihood of both being damaged simultaneously. I took it a step further and completely eliminated the belt driven alternator and even the drive pulley from the flywheel on my airplane. I would argue that my installation having zero moving parts, is simpler than P-mags. That story can be found here:
http://www.vansairforce.com/community/showthread.php?t=162017&highlight=Kissing
 
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Hi Otis. I have some educated opinions on this.

1. Over rev limitation. I agree.
2. Software vs. discrete logic. I agree in general, but at some point software will be embedded in everything. I am working on a new generation trim and flaps controller that works entirely in hardware, but when a CPU is plugged in, additional features are enabled. In this way, the software driven functions work in parallel with the hardware. Sort of like a 'limp home' mode. I think it's reasonable to ask all of the ignition/ecu vendors that use software if they support such a mode.
3. flywheel triggers gives precise, repeatable ignition timing events, whereas accessory case driven timing has gear lash so the ignition timing is 'dithered' around the ideal timing. This may not be a Bad Thing. Just ask the prop vendors about resonances and electronic ignitions. Dithering may reduce these resonances and is a common technique in electronic systems to reduce radiated emissions. Flywheel triggers have their own failure modes that can be nasty. I have had inflight failures with a flywheel system...Yikes!

There is another issue related to electronic ignitions that needs addressing. Many systems allow you to increase the spark gap on your plugs to provide a 'hotter' spark. This means that the spark plug wires operate at higher voltages and are subject to faster degradation and flash-over (misfire). Routing and separation of these wires is more important. I have found that careful gap control is important... make sure all plugs have the same gap and that the gap never exceeds the allowable specs. In fact, bigger is not necessarily better because modern ignitions have long duration lower voltage sparks, rather than short, high voltage sparks.

V

Good points! #2- yes, a reliable hardware based ?limp? mode can be acceptable, but I?d have to climb the learning curve to the point of being able to bench test the unit to satisfy myself that it was really true. #3- I have a Hartzell composite prop with zero resonnance issues so prefer ?dither-free? precision. Anyhow, dithering can be resonant too, potentially EXCITING structural resonance. ****-shots can go both ways!

I agree completely about the importance of spark gaps. Consider especially the dual-coil CDI setups driving two opposing spark plugs. I stand ready to be corrected here, but as I understand it these do not send discreet spark discharges to each plug- but a single discharge that generates both sparks simultaneously, with the engine case serving as the ?connecting lead?. The spark actually goes from the center electrode to the ground electrode on one plug, and from the ground electrode to the center electrode on the other plug, so spark energy-symmetry relies on plug and gap symmetry.
 
SNIP.. I would argue that my installation having zero moving parts, is simpler than P-mags. SNIP

I hear about ?no moving parts? a lot. Perhaps I?m stumbling on:
- The relative motion between the crank magnets and the crank sensor.
- The need for an alternator (an it?s moving parts) to keep the igntion going - unless of course you carry a boatload of batteries to power it all.

As one that flew behind a dual Lightspeed install and pulled both units at 300 hours (replaced with dual pMag) I suggest to readers that the moving part issue is perhaps #82 on the top list of stuff to consider when selecting ignition systems.

Carl
 
I hear about “no moving parts” a lot. Perhaps I’m stumbling on:
- The relative motion between the crank magnets and the crank sensor.
- The need for an alternator (an it’s moving parts) to keep the igntion going - unless of course you carry a boatload of batteries to power it all.

As one that flew behind a dual Lightspeed install and pulled both units at 300 hours (replaced with dual pMag) I suggest to readers that the moving part issue is perhaps #82 on the top list of stuff to consider when selecting ignition systems.

Carl

Touché! But really the only moving part in the ignition itself is the ring securely bolted to the flywheel that carries the little triggering magnets. By comparison P-mags are a hot mess of moving parts.
 
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I hear about ?no moving parts? a lot. Perhaps I?m stumbling on:
- The relative motion between the crank magnets and the crank sensor.
- The need for an alternator (an it?s moving parts) to keep the igntion going - unless of course you carry a boatload of batteries to power it all.

As one that flew behind a dual Lightspeed install and pulled both units at 300 hours (replaced with dual pMag) I suggest to readers that the moving part issue is perhaps #82 on the top list of stuff to consider when selecting ignition systems.

Carl
Failed alternator does not mean immediate ignition fail.

As for motion near the pickup sensor counting as a moving part - that seems like creative accounting. The "moving part" in this case is not a whole new moving part like a new gear or a mag.
 
I hear about ?no moving parts? a lot. Perhaps I?m stumbling on:
- The relative motion between the crank magnets and the crank sensor.
- The need for an alternator (an it?s moving parts) to keep the igntion going - unless of course you carry a boatload of batteries to power it all.

As one that flew behind a dual Lightspeed install and pulled both units at 300 hours (replaced with dual pMag) I suggest to readers that the moving part issue is perhaps #82 on the top list of stuff to consider when selecting ignition systems.

Carl
Carl, why did you remove the dual lightspeeds? curious.
 
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