P-mags and EI... good idea?

[az_gila]

Originally Posted by Toobuilder
To your original combination, why would you run two different types of electronic ignition.

Originally Posted by Ron Lee

Different failure modes.

...some efficiency loss.

Unless both EI systems are working to exactly the same rpm/manifold press/advance chart your two spark plugs in each cylinder will not be firing at the same time.

This must be a slight power loss, even if it not as much as a magneto/EI combination.

I would think you would want matched EI system curves (aka, timing) for peak efficiency.

[Bevan]

Originally Posted by Ron Lee

Different failure modes.

But still independant of each other. What am I missing here? I'm also planning on 2 P-Mags so I'd like to know.

Bevan
RV7A wiring

[Ron Lee]

Originally Posted by KayS

p-mags are self powered. lightspeed is not.

That does not invalidate my point that they most likely have different failure modes.

[N941WR]

Originally Posted by KayS

ok... my understanding was that the lightspeed will fire much less in advance at lower rpm's. somewhere below 25 degrees, but it seems that i was wrong here. i do believe that the combination of lightspeed and p-mags would work. but now i don't see a real benefit here, the p-mags add just cost and complexity in combination with a lightspeed EI. i don't want to say that p-mags are less reliable than slick mags but there should be a higher chance of mishandlng or mistakes during installation for the p-mags.

so, what do you guys think...? is the Lightspeed EI so let's say powerful that it "over-rules" any kind p-mag or slick mag? and if so, from my understanding, the p-mags/slick mags act just as a back up?

Kay, still learning....

Kay,

The P-mag is programmable and can be tuned to your installation. Run the "A" curve and the timing starts around 25 BTC, and 30 BTC for the "B" curve. You can also cap the max advance so for a new engine, you can set the timing to 25 and cap the advance at 25, thus making it act like a mag.

As for reliability of the P-mag vs. LSI, that is a toss-up. If you do a search on the EI section of this board (where this thread belongs, BTW) you will find very few issues with P-mags for the last two or three years. On that search, you will find a number of issues with the LSI over the same time period. I have found that the reliability of the P-mags has improved greatly over the last few years to the point where there have been few, if any issues.

I disagree with your statement about the P-mag adding more complexity. The LSI system is very complex and has a number of connectors (Brain box, trigger, coil pack, and plugs), wiring, wire routing and mounting requirements, including putting the brain box aft of the firewall and passing the wiring bundle through the firewall. With the P-mags you can take them out of the box, plug them in the mag hole, run the power, mag, and ground wires (and jumper if you want to run the "A" curve) and fly them with minimum fuss.

With the addition of an EICommander, you can monitor a dual P-mag installation in flight, change the timing (if desired), and add some functionality that is not available with any other aviation ignition system on the market.

[Danny7]

Originally Posted by N941WR

....including putting the brain box aft of the firewall and passing the wiring bundle through the firewall. .....

With the addition of an EICommander, you can monitor a dual P-mag installation in flight, change the timing (if desired), and add some functionality that is not available with any other aviation ignition system on the market.

with the EICommander you then have a firewall penetration and wiring running to the panel, with a "brain" of some sort on the panel, correct?

[N941WR]

Originally Posted by Danny7

with the EICommander you then have a firewall penetration and wiring running to the panel, with a "brain" of some sort on the panel, correct?

Yes, the EICommander requires you to run the serial wires through the firewall BUT the EICommander is optional and you don't have the issue of trying to run a large connector through the firewall, which you have with LSI.

The P-mags can and will operate without the EICommander. Should either the EICommander or one of its connnections fail, it will not impact the operation of the ignition in any way.

The EICommander comes in two flavors, one with a remote brain box, as seen in these pictures or in the self contained unit which fits in a standard instrument hole. As you can see from the picasaweb pictures, the wire bundle is rather small.

BTW, here are just a few of the features of the EICommander:
• Timing Divergence alarms
• Ignition wiring harness health reporting (open or broken lead as well as shorted or fouled plugs)
• Ability to monitor and display the current E/P-mag timing, internal temps, advance, etc.
• Ability to configure the E/P-mags from your instrument panel, in flight, or on the ground.
• Ability to store multiple E/P-mag timing configurations and send them to the ignition as needed/desired.
• Manifold Pressure and Tachometer which includes alarms for MAP / RPM restricted ranges, not just RPM
• Hobbs and multiple trip set timers
• Optional OAT and carb temp probes.

[KayS]

Hey Ron, i didn't don't agree with you. i strongly believe that you are correct with the different failure modes... just a misunderstanding.

@ the other and especially Bill: thank you so much for your info's. it really helps me to get a more clear picture about the stuff i was buying. :-)

[elippse]

The Carbon Cub comes equipped with dual LSE EIs. There is also a certified helicopter manufactured in France that uses a Plasma EI-magneto combo. The Plasma-series LSE EIs are capacitor discharge units and the Plasma III also has 6-8 sparks at all rpm in very rapid succession, about 80 micro-seconds apart. Compare this to some units which have multiple sparks up to about 2400 rpm that are 2 milli-seconds apart. At 2400 rpm, 80 micro-seconds is 1.15? and 2 milli-seconds is 28.8?.
A capacitor discharge EI, because of its high rate-of-rise voltage will fire plugs fouled with oil or a carbon coating on the insulator, whereas with an inductive system, such a coating may drain off its slow rate-of-rise voltage before it reaches sufficient voltage to fire the plug.
This effect was well known if you had a car that was burning oil. With oil-fouled plugs you couldn't get the plugs to fire, so there was a device you could plug into the spark plug lead which had an internal gap. The gap allowed the voltage to build up until it would jump the gap and put this instantaneous voltage to the plug electrodes which would then fire the plug. Often times too, in trouble-shooting an engine that was running rough you would pull each wire from a plug one at a time and allow the spark to arc to the plug terminal and if the engine started running well, you knew you had found the culprit!
You need to examine all of these features along with cost and arrive at a decision that satisfies your needs.

[Remyswing]

Hello all,
I have an other question about P mags and traditional magneto installed on one engine: how do you install harnesses? do you cross lower an upper cylinder spark plug harnesses or usually or do you use one mag for the lowers and the other one for the uppers? if yes, what is the best: Pmag on lower?
Thanks

[elippse]

A magneto is an inductive spark system. which is activated by a rotating magnet moving through the coil. The magnet, having two poles, N&S, alternates the polarity of its output on each cylinder, giving positive high voltage to one cylinder then negative high voltage to the next, and so on. The center electrode on a spark plug, when heated, acts as a thermionic emitter, generating a potential of 500V to 1000V depending on how hot it is. When the high voltage is negative, this potential adds to it, and when the high voltage is positive, this potential subtracts from it.
In automobiles you were cautioned to make sure that the proper polarity was connected to the coil terminals to insure that it was a negative spark acting in series with the potential from the plug, otherwise the engine may not start or run as well. Because of this polarity reversal, you may want to take this into account when planning how to attach the magneto outputs to the spark plugs.
Remember, too, that a magneto is a generator and that its output voltage varies up and down with rpm. That is why the pure magneto is equipped with an impulse coupler which swings the magnet faster for starting to increase the voltage. Magnetos equipped with auxilliary voltage inputs for starting, such as a shower of sparks, have higher starting volyage.