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One Magneto, One EI

Andrew Anunson

Well Known Member
I have heard that running one magneto, one EI is hard on the mag because the EI runs with advanced timing and the mag does not. Is there any truth to this?
 
Hard on the Mag??

Huh? I've been to two county fairs and a goat race and I've never heard such a thing. We run a LightSpeed Plasma III ignition and a Slick mag on our RV-6 and neither has ever missed a single spark.
 
Same for me...one LSE and one mag...works great. I suspect the EI does all the heavy lifting, when I do a mag check on run up, I get a 50-75 RPM drop with only the magneto selected, but no RPM drop when only the EI is selected. For practical purposes, the magneto is really just backup if the EI fails.
 
doesn't know

The mag doesn't know that the EI just sparked the fuel - it just keeps sparking.
 
I have heard that running one magneto, one EI is hard on the mag because the EI runs with advanced timing and the mag does not. Is there any truth to this?

How does the mag get any feedback from EI firing? I don’t see a feed back mechanism since all a mag knows is the drive gear is turning.
 
So, if I may speculate for my own educational purposes...the timing of the mags is not the same, there is no synch mechanism, no feedback between the mags is required. (Thanks to RV8CH) I’m thinking that doesn’t matter due to the fact that when flying low, the sparks are in synch, and at altitude the slick has fired into a cylinder that has already been fired by an “advanced” spark from the lightspeed, thereby making the slick mag spark no harm/no help? I would also assume that the one slick mage is an impulse type, so as to not to interfere with a smooth start? (This is likely basic stuff..I’ve been out of the recip world for i while).
 
? I would also assume that the one slick mage is an impulse type, so as to not to interfere with a smooth start? (This is likely basic stuff..I’ve been out of the recip world for i while).

Most Lycoming engines are set up to start on one ignition only, so most owners choose to start on the EI and use a non-impulse mag on the other side, grounded out during start.
 
Spark in the dark...

I've operated three different RV's in a One mag, One EI configuration for 25 years and over 4000 hours. No issues whatsoever. In fact, the mag is actually the weak link.
Way back when Vans aircraft was at North Plains and bragging rights were how light and how cheap your RV was, electronic ignition was relatively new. I met Jeff Rose at a fly-in and bought his first Electroair EI prototype and bolted it on my RV4 with a Slick partner. The EI was so much smoother and such a more efficient spark as were the automotive spark plugs that when my Slick failed inflight I didn't notice until the mag check on a subsequent flight. Since then I've had his systems on my HR2 (IO540C4B5) and replaced my RV4's with a newer version from Jeff (now Mike) before I sold it. The new owner reports great performance.

That original 1994 prototype Electroair system I bought from Jeff? It's running strong alongside a P-Mag on my RV6X, Dual EI...:)

Questions?
Smokey
 
Last edited:
SNIP... In fact, the mag is actually the weak link.

+1

I’ve been running dual pMags for over a decade and recommend them.

My RV-10 started life with mags and I hated them. I especially hated maintaining the overpriced aircraft plugs. That plane is now happily flying with the new six cylinder pMag.

Carl
 
+1

I’ve been running dual pMags for over a decade and recommend them.

My RV-10 started life with mags and I hated them. I especially hated maintaining the overpriced aircraft plugs. That plane is now happily flying with the new six cylinder pMag.

Carl

Carl, I'm sure looking hard at the 6 cyl P Mag and SureFly Mag.
Pretty similar costs except the SureFly keeps aircraft plugs.
The P-Mag has about 4 degrees less max timing advance.
I'm not really at a good point to replace, left mag with impulse couple at about 300 hours since fact reman. /the right non-impulse at less than 30 since 500 hour inspect and repair. Both I believe have the impulse coupled style cushioned hook up to gears. Sounds like on either side will have to get gear and change the mounting studs.
What kind of fuel savings are you seeing? I assume hot starts are now a non-factor,
Thanks
 
Kelly,

I recommend you look over the six cylinder pMag installation guide: https://emagair.com/wp-content/uploads/2020/08/Manual-P200-6XLycoming-V40.pdf

During installation you set both the base timing and whatever you want for max timing. For the RV-10 I recommend 25 degrees base and 34 degrees max as my reading indicates that for typical RV flying this provides the best overall timing profile.

Fuel savings are ~10% when high and LOP. Engine start is a blade or so.

You do need to replace the mag mounting studs for shorter ones when you swap out the mag for the pMag, but if memory serves I think Brad at pMag now provides the needed replacement studs with the pMag install kit. Other than that the pMag goes in just like your mag.

As far as keeping aircraft plugs, why? They are expensive and a PITA to clean and keep gapped. I run NGK BR8ES plugs on both the six and four cylinder pMags.

Most (but not all) EIs are better than a mag, but only the pMag can be considered a “drop in replacement”. Any other option requires some consideration of making sure power gets to the EI(s) after something in your electrical power distribution fails.

Carl
 
Kelly,

I recommend you look over the six cylinder pMag installation guide: https://emagair.com/wp-content/uploads/2020/08/Manual-P200-6XLycoming-V40.pdf

During installation you set both the base timing and whatever you want for max timing. For the RV-10 I recommend 25 degrees base and 34 degrees max as my reading indicates that for typical RV flying this provides the best overall timing profile.

Fuel savings are ~10% when high and LOP. Engine start is a blade or so.

You do need to replace the mag mounting studs for shorter ones when you swap out the mag for the pMag, but if memory serves I think Brad at pMag now provides the needed replacement studs with the pMag install kit. Other than that the pMag goes in just like your mag.

As far as keeping aircraft plugs, why? They are expensive and a PITA to clean and keep gapped. I run NGK BR8ES plugs on both the six and four cylinder pMags.

Most (but not all) EIs are better than a mag, but only the pMag can be considered a “drop in replacement”. Any other option requires some consideration of making sure power gets to the EI(s) after something in your electrical power distribution fails.

Carl

Thanks Carl, you answered my questions. Now the only question is whether
I can sell either of my Bendix S-1200 mags to help offset the ~$1900 cost. and when to do the deed.
 
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