Which mag to ditch for single EI

It appears to me that the right mag is usually replaced when a single EI is installed usually to retain the impulse coupled mag for starting purposes.

I have heard someone suggest that the left mag is the most mechanically complex and should be the 1st to go. Starting is not an issue due to the fact that if you have enough juice to spin the starter then you have more than enough to fire the EI. Even if you can't turn the engine over there is a decent chance there's still enough voltage to fire the plugs with a hand prop.

Curious to hear from those that have done this and their thoughts on it.

I replaced both ignitions with PMags so this does not answer your question, but starting when the battery has gone flat due to me leaving the master on has not been an issue, hand propping usually has the engine running on the second pull through.

Cheers

I replace the impulse coupled mag first. A failed impulse coupling could drop it's damaged self into the gears of the accessory case, causing the engine to fail.

Normally you keep the impulse coupler to facilitate starting if the EI fails or battery is dead and then that differs between Lightspeed and P-Mag. Of course that might then beg the question who cares if you start and don't intend to fly on one ignition if it wasn't just the battery.

But yes, it's imperative to inspect the coupler along with the mag at regular intervals. Mine was going south at 500 hours on the mag and yes, it's failure will make a big mess!

Here's another vote for impulse mag on the left and EI replacing the right mag, has worked great for me for 670+ hours.

Here's another vote for impulse mag on the left and EI replacing the right mag, has worked great for me for 670+ hours.

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You'll be able to hand prop it even with a dead battery.

Same set up for me and I always start on both, starts like a car.

Concerns about the complexity of the impulse coupling are valid but hundreds of thousands of airplanes are flying with them and aren't given it a second thought.

Keeping the non impulse coupled mag will force you to start on the EI only or else you'll loose teeth on the ring gear.
needless to say you won't be going anywhere with a low or dead battery.

Glas467 said:

Here's another vote for impulse mag on the left and EI replacing the right mag, has worked great for me for 670+ hours.

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Same here. I had toggle switches and never could start the engine on the Lightspeed alone. It came online once started with the impulse mag. Had about the same amount of hours as above when sold.

LIghtspeed on left, slick mag on right

My engine starts on the Lightspeed just great. Part of my decision was easier because my engine didn't come with an impulse coupling mag. Instead it came with a dual point mag on the left, made to use with a "shower of sparks" ignition box.
I didn't want to bother with all that, so I ditched it.
If I had an impulse-coupled mag, it would have been a harder decision, not sure what I would have done.

I've found with a light composite prop, I don't think I could hand prop it anyway, just not enough inertia to get it to swing through. Maybe with an impulse coupled mag it would fire anyway?

Excuse the thread drift, but another issue with hand propping for me is with bendix FI, on a warm engine, it takes a lot of cranking with WOT and full lean to get it unflooded. So I doubt I could ever hand prop a warm Lycoming with FI. Not an issue with a cold engine, it usually fires on the second blade.

Thanks for the input so far everyone.

I have spoken to Brad at Emag and he said he prefers to replace the left mag with pmag but I have decided not to go with his system.

Klaus said that he would pull the left mag and leave the right and leave all the starting up to the plasma as well.

Personally don't know anyone that runs this way but it does have merit. Just want to make sure there isn't surprises I haven't thought of.

Kokemiller said:

Personally don't know anyone that runs this way but it does have merit. Just want to make sure there isn't surprises I haven't thought of.

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Given that direction you'll have two potential issues:
1. how will you start with a dead battery?
2. how will you start with a bad EI?
I've had both, #2 several times.
Good luck.

Kokemiller said:

Thanks for the input so far everyone.

I have spoken to Brad at Emag and he said he prefers to replace the left mag with pmag but I have decided not to go with his system.

Klaus said that he would pull the left mag and leave the right and leave all the starting up to the plasma as well.

Personally don't know anyone that runs this way but it does have merit. Just want to make sure there isn't surprises I haven't thought of.

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Kelley,

I have the LightSpeed Plasma III and installed it exactly as Klaus recommended as stated above. I have the LS on the left firing the top plugs and a non-impulse mag on the right firing the bottom plugs. I have almost 1000 hours on my plane and I have never had an issue starting on the LS only, cold or hot. I have had other issues with the LS, intermittent missing due to a bad Hall effect, but never starting problems. I have toggle switches and on my checklist flow I come to the LS first and leave the mag off. You could do some fancy wiring to ground the mag when the starter is engaged, but it isn't necessary.

Also, I have a 200 hp IO-360A1A angle valve motor. Even if I had an impulse mag, I don't think I would want to hand prop it. Being fuel injected, it does take a few rotations during a hot start. So even if I dared hand propping, I doubt I would be very successful starting on just an impulse mag. It would take a while at the very least. If I should ever have a dead battery, I would put it on a charger and go have lunch!

If the LS goes bad prior to start, well then I guess I'm grounded. I shouldn't be flying on a single ignition anyway. The good thing about the the RV and the VAF community is that help is usually right around the corner. Parts can be shipped overnight. The trip could turn out to be a nice adventure!

Jerry Esquenazi
RV-8 N84JE

I find it somewhat comical how each manufacturer thinks their system is better for starting. Leaving the impulse mag gives you an out. Either way the mag should come off at 500hrs for inspection. My vote is for always keep the impulse. On my Citabria, I converted the Lyc to dual impulse.

osxuser said:

Leaving the impulse mag gives you an out.

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An out for what, may I ask? Not trying to ba an ***, but I have to agree with Jerry. Why would you consider taking off with only one ignition system working?

An out for what, may I ask? Not trying to ba an ***, but I have to agree with Jerry. Why would you consider taking off with only one ignition system working?

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1: An out for a dead battery
2: If your battery is dead and your alternator is not working you really wouldn't take off but that scenario would be rare.

In Jerry's situation with an angle valve and probably high compression piston
I agree, out of luck.

I am thinking of the more common scenario, sitting somewhere for an extended period of time and your battery going dead on you and out of cell phone range of nearby RV friends.