Surefly electronic ignition question

[PT20J]

Since it's a wasted spark system, the plugs fire twice as often (two plugs always fire at the same time -- the "wasted" one fires during an exhaust stroke). I asked if this would wear the plugs out faster and Surefly said no, but I wonder if it might not be better to use fine wire plugs.

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[carusoam]

Skip...

The cause of plug erosion is the spark... isn’t it?

Not the flame...

or is it both..?

Then again, i’m Not sure...

 

I would expect the high energy of the spark to knock atoms off the surface on a regular basis...

Having a wasted spark, probably isn’t free... it has some costs...

PP thoughts only, not a mechanic...

Best regards,

-a-

[ArtVandelay]

Extra spark should help keep the plugs from fouling.


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[Oscar Avalle]

Since it's a wasted spark system, the plugs fire twice as often (two plugs always fire at the same time -- the "wasted" one fires during an exhaust stroke). I asked if this would wear the plugs out faster and Surefly said no, but I wonder if it might not be better to use fine wire plugs.
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Electroair recommends fine wire plugs.


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[Bob_Belville]

I talked to the engineer who was responsible for the "mechanical" aspect of the Surefly EI while I was at KOSH. (I did not get his card/name... no nonsense guy, fwiw he's older than I am!) 

At that time lead time for their 4 cyl model was 3-4 weeks, the 6 cyl model is sold further out.

My takeaway, I could have misunderstood his answers, was that the timing advance will come into play at higher altitudes and at lower power settings. And though the device might be capable of 38 BTC, realistically, real world, it will be about 28 BTC.

I am ordering mine right after I pay my next AX card which will include 500 gallons of 100LL from the 7500 nm trip to AirVenture and points west.    

[PT20J]

We probably all know that the magneto ignition system reverses polarity every firing. That's why we rotate plugs. Since the spark jumps from cathode to anode, taking a bit of metal with it, if we didn't rotate the plugs the ground electrodes would erode on half the plugs and the center electrode would erode on the other half. Rotating (in an engine with an even number of cylinders, i.e., non-radials) evens out the wear.

https://www.themagnetoguys.co.uk/spark-polarity

A bit of research shows that wasted spark systems for automobiles tended to use plugs with platinum on both electrodes because of alternating polarity and twice the number of sparks.

https://en.wikipedia.org/wiki/Wasted_spark

https://shop.advanceautoparts.com/r/advice/car-maintenance/the-differences-between-spark-plugs

Does this apply to airplane engines and Surefly ignition? Maybe... Massive aviation spark plugs have much larger electrodes than automotive plugs -- maybe they can take the extra sparks in stride. Also, the wasted spark occurs on the exhaust stroke with higher gas temperatures and lower cylinder pressures, so the plug fires easier with much less energy in the spark to move metal.

If I were installing a Surefly and had serviceable massives, I'd keep them so that I would only be changing one component of the ignition system. Then I could determine what advantages Surefly might have. When the plugs wore out, I'd change to fine wires.

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[DXB]

Another possibly dumb question-  If the surefly is using variable timing and the conventional mag has fixed timing , a fouled plug driven by the surefly would seem problematic because the ignition timing on the affected cylinder could become way off from the others.  Am I wrong here? Is the Surefly system smart enough to deal with this issue?  

[takair]

15 minutes ago, DXB said:

Another possibly dumb question-  If the surefly is using variable timing and the conventional mag has fixed timing , a fouled plug driven by the surefly would seem problematic because the ignition timing on the affected cylinder could become way off from the others.  Am I wrong here? Is the Surefly system smart enough to deal with this issue?  

I think it would lead to slight roughness, but you are at a relatively low power setting so I can’t see it causing damage.  I would think you could quickly diagnose with an analyzer.  That said, in my experience, en route plug fouling should be rather rare.  Are you seeing this occurring with some frequency in your plane?

[ArtVandelay]

Another possibly dumb question-  If the surefly is using variable timing and the conventional mag has fixed timing , a fouled plug driven by the surefly would seem problematic because the ignition timing on the affected cylinder could become way off from the others.  Am I wrong here? Is the Surefly system smart enough to deal with this issue?  

The pressure builds up as the mixture compresses, I doubt a slightly delayed start will effect the balance that much, we’re talking about millisecond(s). I’ve had mistimed magnetos, I only could tell by looking at engine monitor data. I assume that FAA required testing of failure modes, with one or more plugs failed.

[PT20J]

Pretty good discussion of the Surefly timing advance here

http://www.vansairforce.com/community/showthread.php?p=1350922

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[McMooney]

7 hours ago, PT20J said:

Pretty good discussion of the Surefly timing advance here

http://www.vansairforce.com/community/showthread.php?p=1350922

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that's helpful, was just thinking, I have no way to test or know how to take advantage of the new surefly.

wish the documentation came with an official chart. 

from the post, i'm getting I need to learn LOP.

[cliffy]

Going back over 50 years ago to A&P school, we were taught that when the plugs fire at the same advance settings, (remember we try to get the mag timing lights to go out at the same time when timing both mags?) the flame fronts started at each plug advance toward the center of the combustion chamber and meet there if all goes well.  I just wonder if one fires at say 25 BTC but the other starts earlier at say 28 or 29 degrees would this cause an imbalance in the flame fronts setting up some vibrations, wear patterns, harmonics not normally seen with simultaneous firing spark plugs. 

[carusoam]

43 minutes ago, cliffy said:

Going back over 50 years ago to A&P school, we were taught that when the plugs fire at the same advance settings, (remember we try to get the mag timing lights to go out at the same time when timing both mags?) the flame fronts started at each plug advance toward the center of the combustion chamber and meet there if all goes well.  I just wonder if one fires at say 25 BTC but the other starts earlier at say 28 or 29 degrees would this cause an imbalance in the flame fronts setting up some vibrations, wear patterns, harmonics not normally seen with simultaneous firing spark plugs. 

Interesting thought, Cliffy.

All of those things would happen... just the engine would soldier on as if they were nicely balanced...

It would take good instrumentation to show something is amiss... and a keen eye on the charts...

The extreme situation occurs when one plug doesn’t fire, and it is hardly noticeable without turning off the other mag intentionally...

When two mags are timed differently, the individual EGT peaks are different, during the run-up...

The big difference is how much fuel burns to completion before exiting the exhaust valve...

Under extreme LOP conditions you might see the effects better... As fuel gets too rare to burn, gets mixed with less than ideal ignition spark...

micro seconds and flame front speeds really start getting interesting as the variables increase...

Hope Ross finds this thread...

PP thoughts only, not a mechanic 

Best regards,

-a-

 

[kortopates]

46 minutes ago, cliffy said:

Going back over 50 years ago to A&P school, we were taught that when the plugs fire at the same advance settings, (remember we try to get the mag timing lights to go out at the same time when timing both mags?) the flame fronts started at each plug advance toward the center of the combustion chamber and meet there if all goes well.  I just wonder if one fires at say 25 BTC but the other starts earlier at say 28 or 29 degrees would this cause an imbalance in the flame fronts setting up some vibrations, wear patterns, harmonics not normally seen with simultaneous firing spark plugs. 

 

3 minutes ago, carusoam said:

Interesting thought, Cliffy.

All of those things would happen... just the engine would soldier on as if they were nicely balanced...

It would take good instrumentation to show something is amiss... and a keen eye on the charts...

The extreme situation occurs when one plug doesn’t fire, and it is hardly noticeable without turning off the other mag intentionally...

When two mags are timed differently, the individual EGT peaks are different, during the run-up...

The big difference is how much fuel burns to completion before exiting the exhaust valve...

Under extreme LOP conditions you might see the effects better... As fuel gets too rare to burn, gets mixed with less than ideal ignition spark...

micro seconds and flame front speeds really start getting interesting as the variables increase...

Hope Ross finds this thread...

PP thoughts only, not a mechanic 

Best regards,

-a-

 

We can easily see split timing as little as 1/2 degree difference from a LOP Mag test in the downloaded data- its pretty obvious actually. But I don't think anyone could see that in the cockpit doing the test. You need to be able to see the isolated mags side by side in the downloaded data. 

[cliffy]

My reasoning was not in a momentary mag check or a short flight continuation after a mag failure but in long time (hrs upon hrs) of running to TBO with split timing. I'm sure that Lyc or Cont has given some thought to split timing issues but maybe not for the entire TBO run. 

I also realize that my training had more to do with large radial engines than the little tiny flat fours (my runable project was to get a B-25 with P&W 2600s running after 5 years of sitting idle).

We were doing ignition monitoring with electronics on big radials (electronic ignition analyzers in real time) way before the little guys even thought of analyzers. 

All this may not be as important in say a 180 Lyc but step it up to the higher stressed 6s and maybe it plays a bigger part. 

[Andy95W]

I was taught the same way so I asked this exact question of the Electroair guys and they said it didn't make any difference.  Not sure if they were BSing me or not.

Doing a magneto check at high power doesn't seem to make any difference, nor does it seeem to cause any significant issues in high performance cars with only a single spark plug that is not centrally located.  Maybe they were telling the truth.

[Guest]

Some Continental engines do have split magneto timing from new.

Clarence

[J0nathan225]

On 8/9/2019 at 10:08 AM, Bob_Belville said:

I talked to the engineer who was responsible for the "mechanical" aspect of the Surefly EI while I was at KOSH. (I did not get his card/name... no nonsense guy, fwiw he's older than I am!) 

At that time lead time for their 4 cyl model was 3-4 weeks, the 6 cyl model is sold further out.

My takeaway, I could have misunderstood his answers, was that the timing advance will come into play at higher altitudes and at lower power settings. And though the device might be capable of 38 BTC, realistically, real world, it will be about 28 BTC.

I am ordering mine right after I pay my next AX card which will include 500 gallons of 100LL from the 7500 nm trip to AirVenture and points west.    

Nice! Bob is AGL going to do the install?  I'm coming back to the mooney ownership realm after a very long 4 months! The new bird will need an annual and possibly a surefly in December! Photos to follow, post closing of the deal. 

Jon.

[jamesm]

Not to stir the pot too much.... The title of the post says "Surefly  electronic ignition question"
I believe there might be a slight difference between Electro-Air and  Surefly electronics Ignition systems.

ElectroAir has a bunch of remote boxes that  you will have to find room for both inside cabin as well  in the Engine compartment  the have reduced by one but still in a Monoey  it can be tricky. I have heard that the earlier ElectroAir Ignition leads  have to spaced a certain distance a part for EMI. I guess the newer leads being used take away the spacing limitation.My understanding is that that Electroair uses wide  gap than normally use previously  in aviation (0.022-0.016)  and higher voltage as well

Surefly is more of a self contained unit containing all remotely mounted boxes.. uses standard  Slick Harness and Spark plugs. So if you have a Bendix Magneto harness you have to order Slick style harness and will have to remove the gear off  the Magneto that you replacing onto the Surefly Ignition Module (Magneto).

It was explained to me If I am understanding it correctly...when I asked about higher voltage effect versus magneto  voltage. something like this you can push out so much energy across the spark plug gap and Having super higher energy plug isn't going to give only certain amount  efficiency versus the change  advancement of the Mag timing is going to give most return on the change in timing.  I was unaware of the  valid  points that Cliffy has brought up.

 

 

 

 

[Ragsf15e]

On 8/10/2019 at 8:44 AM, PT20J said:

Pretty good discussion of the Surefly timing advance here

http://www.vansairforce.com/community/showthread.php?p=1350922

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Did any of you guys read this and have any thoughts on their conclusions?  The experimental folks seemed to say that the advance schedule is a “one size doesn’t fit all” solution for lots of engines.  Specifically for our angle valve io360s, they said the optimum advance is something around 28 degrees.  The Surefly can go all the way up to 36.5 at 2700rpm.  Basically they said the advance is way past optimum for us and not going to improve performance much, but will result in higher temps for sure.

Im definitely hoping to get one for easy maintenance, starting, etc, however if the temps are higher, I’d at least like a little more speed or economy? 

[jetdriven]

They should program it to the engine that it goes on. Not all engines have the same advance curve

[Bob_Belville]

Nice! Bob is AGL going to do the install?  I'm coming back to the mooney ownership realm after a very long 4 months! The new bird will need an annual and possibly a surefly in December! Photos to follow, post closing of the deal. 
Jon.

Jon, sure, Lynn will install. Look forward to seeing you again!


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[Ragsf15e]

11 hours ago, jetdriven said:

They should program it to the engine that it goes on. Not all engines have the same advance curve

That would be nice, but I don’t think they do that with the Surefly.  The curve on their website is what you get no matter your engine.

[jetdriven]

It’s too Generic. For the IO the advance curve is too aggressive. Yet other engines could use more.  They could have DIP switches and three advance curves. 1 is the least and 3 is the most. 

[PT20J]

5 hours ago, Ragsf15e said:

That would be nice, but I don’t think they do that with the Surefly.  The curve on their website is what you get no matter your engine.

Where did you find the curve on Surefly’s website? I looked all over and couldn’t find it. I emailed them (twice) asking for it but so far no dice. 

Interesting that Lycoming’s rebranded version is set for fixed timing.

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