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  #11  
Old 09-09-2018, 09:38 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Alan Carroll View Post
I've got dual Lightspeeds and if I turn one off in flight there are no popping noises. I agree with Carl's suggestion, you should check out the Lightspeed more carefully. Could be the the mag has been masking a problem with the EI, which only became evident when the mag plugs became fouled?
+1

As I mentioned above, the popping is an indication of intermittent misfires (the key here is intermittent) and a misfire typically requires a lack of ignition when a proper fuel/air mixture exists in the chamber (proper meaning combustible - too lean or too rich it becomes un-combustible). Either plug can effectively ignite the charge and it will FULLY burn. The issue about effective timing with two plugs is only relevant to when the combustion event's peak pressure occurs, relative to the desired point in crank rotation.

The fact that you are getting intermittent misfires indicates that in those occassions of popping, at least one cylinder (possibly all) had no ignition from either plug, assuming there were no issues with mixture and those are unlikely with your intermittent condition. That said, intermittent misfires are likely to occur right on the brink of too lean to combust. But this doesn't match your symptoms as I read them.

Note that a spark VERY early or VERY late will not ignite the mixture, so you are also looking at CPU issues on the LS and not just a lack of spark.

Given the fouled plugs on the mag, it seems most logical that you were running on just the LS and it is intermittently not sparking a cylinder or intermittently drifting the timing in a radical fashion. Note that running on an EI with advanced timing will make it very hard to detect if the mag is not firing. It does impact performance, but not that much and typically not enough to notice it without really paying attention.

Given the intermittency, a bad coil on the LS is a prime suspect. They often fail intermittently.

Larry
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Last edited by lr172 : 09-09-2018 at 12:35 PM.
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  #12  
Old 09-09-2018, 11:57 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is online now
 
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+1 on what Larry said.

I again suggest you take a close look at the Lightspeed. With all due respect to your two A&Ps, they may not have experience with Lightspeed failures.

Carl
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  #13  
Old 09-10-2018, 05:43 AM
deek deek is offline
 
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As you have the only hole in the accessory case filled with your Bendix, you must have a crank triggered LSE. If you have the old RG58 (black) coax cables from the LSE box to the coil primaries, get rid of them and use RG400 (what Klaus currently supplies)

Even if that's not the problem, it will be - sometime, someday... I have over 5,000 hours aggregate experience with LSE 2 in 3 EAB planes; PM me if you need help checking the system out. If you decide to call Klaus, suggest you first read the manual again
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Last edited by deek : 09-10-2018 at 05:46 AM.
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  #14  
Old 09-10-2018, 06:31 AM
fixnflyguy fixnflyguy is offline
 
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Default Electrode short/dirty plugs?

I run an O320H2AD in my -4, with the standard D3000 magneto, and a few months ago I had similar misfire pop/bang during run-up, which I thought was just fouling plug because I hadn't leaned during taxi as I usually do. Cleared it up with the normal power/lean run and took off. During cruise it started again...quick RTF and look under the hood. I had a plug with a cracked insulator and a piece of it jammed in the electrode causing an intermittent short out. Replaced the plug, and good to go. Your problem may have nothing to do with the LS, and simply the dirty plugs.
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  #15  
Old 09-10-2018, 10:00 PM
scsmith scsmith is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
Bryan,

I agree your assumption that the LightSpeed should have fired the cylinders even with the mag plugs fouled is correct. Standard in flight mag (or EI) checks should result in a few RPM drop (FP prop). For dual EI setups turning off one side should be hardly noticeable.

I suspect you have not yet found the root problem. I would start going through the LightSpeed system.

Carl
No doubt this is true ROP. If you are very LOP, not so true at all.
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  #16  
Old 09-10-2018, 10:01 PM
scsmith scsmith is offline
 
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Quote:
Originally Posted by Alan Carroll View Post
I've got dual Lightspeeds and if I turn one off in flight there are no popping noises. I agree with Carl's suggestion, you should check out the Lightspeed more carefully. Could be the the mag has been masking a problem with the EI, which only became evident when the mag plugs became fouled?
Sure, if you are ROP.

Try it 60° LOP and see what happens
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RV-8 N825RV
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also LS-6-15/18 sailplane
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  #17  
Old 09-10-2018, 10:36 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by scsmith View Post
Sure, if you are ROP.

Try it 60° LOP and see what happens
I can’t think of a reason why anyone would get afterfires on one ignition instead of two. It shouldn’t matter how far lop or rop you are.

Larry
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  #18  
Old 09-11-2018, 12:12 AM
scsmith scsmith is offline
 
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Quote:
Originally Posted by lr172 View Post
I can’t think of a reason why anyone would get afterfires on one ignition instead of two. It shouldn’t matter how far lop or rop you are.

Larry
Well, that's true, I don't get afterfires. What I get is a very rough-running engine. But you are right, I don't get pops and bangs. As you pointed out, with one ignition, it will still burn, it's just way late in the cycle and acts like a partial misfire. So if the afterfires (pops and bangs) are the only real symptom that the OP is experiencing, then my point is out of line, and it must be an intermittent ignition problem.
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Last edited by scsmith : 09-11-2018 at 12:15 AM.
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  #19  
Old 09-20-2018, 05:55 PM
blaplante blaplante is offline
 
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Default Some more findings

Thanks for the many ideas. I've found some more root cause that I think explains the trouble. Since the electronic mag was mag checking OK, those plugs were left alone until after my return. On pulling those... I found one of the recommended iridium plugs had no fine wire left. Surprisingly the LSE was still firing this plug (well most of the time I guess). So I think what happened was the fine wire vanished, making the gap too big, which caused the electronic ignition to periodically not successfully fire, but the leaded up Mag plug wasn't in good shape either... hence afterfire. Notably the mag check before takeoff was fine.

per Lightspeed those Iridium plugs should be good for at least 300 hours. I was under 250 when this happened. I've now replaced all the plugs, and will be replacing the iridium plugs more often in the future.

Also, on the recommendations here, I checked the primary Lightspeed coax (it's rg400) and the connections to the spade lugs on the coils... I did find one that was a bit loose & replaced that.
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  #20  
Old 09-21-2018, 08:17 AM
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FasGlas FasGlas is offline
 
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Lightspeed EI's are notorious for bad coils. They are used on German snow mobiles. Klaus imports them for his ignitions.
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