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  #41  
Old 08-08-2022, 12:32 AM
Narwhal Narwhal is offline
 
Join Date: May 2019
Location: Anchorage, AK
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Ok, I couldn't wait until tomorrow, and swapping the coil packs for the affected #2 cylinder didn't look too difficult, so I went out tonight and tried the swap.

Sure enough, the problem moved from the left ignition to the right ignition when I swapped the coil pack powering the #2 top and #1 top spark plugs (off the left module) for the coil pack powering the #2 bottom and #1 bottom spark plugs(off the right module). Now, the problem only presents when the ignition is on both or only the right one is on, the opposite as before.

The #2 cylinder was still the one showing low/erratic temps during the engine runup/popping, which makes sense because the problem probably swapped from the #2 top spark plug to the #2 bottom spark plug.

So I now I'm hoping a new coil pack will do the trick, although at this point I'm not going to get my hopes up too high.
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  #42  
Old 08-08-2022, 08:59 AM
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skylor skylor is offline
 
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Originally Posted by Narwhal View Post
Ok, I couldn't wait until tomorrow, and swapping the coil packs for the affected #2 cylinder didn't look too difficult, so I went out tonight and tried the swap.

Sure enough, the problem moved from the left ignition to the right ignition when I swapped the coil pack powering the #2 top and #1 top spark plugs (off the left module) for the coil pack powering the #2 bottom and #1 bottom spark plugs(off the right module). Now, the problem only presents when the ignition is on both or only the right one is on, the opposite as before.

The #2 cylinder was still the one showing low/erratic temps during the engine runup/popping, which makes sense because the problem probably swapped from the #2 top spark plug to the #2 bottom spark plug.

So I now I'm hoping a new coil pack will do the trick, although at this point I'm not going to get my hopes up too high.
This sounds like progress!

Skylor
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  #43  
Old 08-08-2022, 09:49 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Originally Posted by Narwhal View Post
Y

I inspected that coil's wires as closely as possible. I did the troubleshooting tests from the lightspeed flow charts (I think and hope my avionics tech alraeady did this) and everything passed. Resistance betwen the coil pack +/- input terminals was 1 ohm, and the resistance between the output towers and the positive input terminal was O.L. Additionally the resistance between the center conductor and ground on the wire was O.L. (the wire coming from left ignition module A output to the ignition coil, which is the one my contact said was broken).
Coils vary a good bit, however, you typically see 2-8 ohms on the primary winding (between the two teminals you mentioned that feed power to the coil) and 10K to 20K ohms on the secondary winding (between output center terminal and ground). The fact that your secondary winding reads open likely points to a bad coil. Wasted spark coils are a bit different, so call LS and get advice on best way to measure the coils and the specs for those coils.

Larry
Larry
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Last edited by lr172 : 08-08-2022 at 10:05 AM.
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  #44  
Old 08-08-2022, 09:55 AM
lr172 lr172 is offline
 
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As alluded to previously, the LSE boxes do not have microprocessors and do not have software - Klaus advertises this as a selling point. Please see the attachment from LSE's website:
"Solid-State, Discrete logic (no microprocessor) for maximum reliability: No Software & No Software Updates"
Skylor
logic and software are mostly synonomous. Software is nothing more than logic that is read by a microprosessor and converted to binary instructions for the hardware to follow. Logic can also be burned onto a chip that does the processing of the logic and also provides those binary instructions. Either way it is the same thing once you get down to binary instructions at the hardware level. I agree that burning logic to a chip is safer than a microprocessor executing s/w instructions (several layers of flow and therefore failure points are eliminated), however, at the end of the day hardware at this complexity level doesn't do anything without instructions from something that can process logical constructs.

Larry
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Last edited by lr172 : 08-08-2022 at 10:10 AM.
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  #45  
Old 08-08-2022, 10:40 AM
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skylor skylor is offline
 
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logic and software are mostly synonomous. Software is nothing more than logic that is read by a microprosessor and converted to binary instructions for the hardware to follow. Logic can also be burned onto a chip that does the processing of the logic and also provides those binary instructions. Either way it is the same thing once you get down to binary instructions at the hardware level. I agree that burning logic to a chip is safer than a microprocessor executing s/w instructions (several layers of flow and therefore failure points are eliminated), however, at the end of the day hardware at this complexity level doesn't do anything without instructions from something that can process logical constructs.

Larry
That’s not exactly true. It is possible and it used to be quite common to construct electronics purely from analog and discreet logic components that do not have any “burned” chips at all, and I think this is how the light speed boxes are constructed. These electronics are constructed from transistors, 74LS series discreet chips (which are themselves just arrays of transistors), 555 timers, RC and RL circuits, etc. Again, no programmable logic, PROMs, EPROMs, EEPROMs, flash, etc. Adjustable features of such systems are simply controlled by DIP switches or changing resistor values. Ignition systems are relatively simple and do not necessarily need any logic “instructions” to control their functions, including spark advance.

Skylor
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  #46  
Old 08-08-2022, 11:35 AM
lr172 lr172 is offline
 
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That’s not exactly true. It is possible and it used to be quite common to construct electronics purely from analog and discreet logic components that do not have any “burned” chips at all, and I think this is how the light speed boxes are constructed. These electronics are constructed from transistors, 74LS series discreet chips (which are themselves just arrays of transistors), 555 timers, RC and RL circuits, etc. Again, no programmable logic, PROMs, EPROMs, EEPROMs, flash, etc. Adjustable features of such systems are simply controlled by DIP switches or changing resistor values. Ignition systems are relatively simple and do not necessarily need any logic “instructions” to control their functions, including spark advance.

Skylor
I didn't design it and you may be correct. However, it needs to sense a magnet pulse, relate that to TDC via an offset of degrees (inferred by time) and deal with error handling on that input, as well as a changing wave form as the RPMs change. It then needs a table that moves the timing advance based upon both RPM and data from a map sensor. Also needs an RPM threshhold to further reduce timing for starting RPMs, etc. It also needs to deal with coil dwell timing (to avoid burning up the coil at low RPMs) and numerous other factors. Just don't see how this is all done with timer circuits and transistors. The trigger pulse time interval is constantly changing with RPM, so basic timers don't help here; you need logic to translate interval spans to the delay of spark from the pulse. Degrees from trigger to TDC requires computation to know how fast the crank is spinning so that time can be used instead of degrees and that time is based upon computations based upon time between triggers, which is constantly changing with RPM. The computer cannot measure in degrees from trigger to TDC; Instead, it must use time to approximate degrees and this time is computed from the time between triggers and that time is based upon RPM.

No need to debate it. I was just stating that I didn't know the logic used for crank trigger sensing and error handling and I am pretty confident that meaningful logic is involved here, regardless of how it is done. I have installed several open source EFII systems and have a good grasp on the breadth of logic involved to make them work. That said, I am a software guy and cannot trully appreciate what can be done with the components you mention. I AM smart enough to know not to argue with a EE. One thing I know is that much logic and math is involved.

Maybe this is all done through transistors and that would explain why a failing coil could cause inaccurate RPM readings which would not occur in most EI systems, as they compute RPM based upon crank trigger counting and not coil triggering.

Lary
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Last edited by lr172 : 08-08-2022 at 12:09 PM.
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  #47  
Old 08-10-2022, 01:51 AM
Narwhal Narwhal is offline
 
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Well, replacing the coil pack that powers the #2 and #1 top spark plugs fixed it! I'm pretty happy about that! Thanks Van's Air Force for all your help!

Before replacement, we did a "spark test" of the coils by spinning the prop slowly by hand with the spark plug wires disconnected & fuel off, but with the coils still connected to the ignition modules and the ignition systems on. All of the other coils would send an arc between the two output towers of the coil packs at the appropriate time in the firing sequence, but the upper left coil output tower for the* #1 upper plug wouldn't arc to the #2 upper plug tower, it would arc instead from the #1 upper plug output tower*to one of the bolts that holds the coil pack bracket to the airframe. Aside from that, I'm not sure what went wrong.

Also, we noticed that the coil pack for the #1 and #2 bottom plugs was arcing through the case due to a hairline crack in both tower cases, and not from the tower tips, but changing that coil pack had no effect on the problem. The problem cleared up when I changed the coil pack powering the #1 and #2 top plugs alone.

So, yeah. On a lightspeed ignition, apparently some kind of breakdown inside a coil pack can cause the tach to read 20-30% high and swing erratically +/- 300 RPM with actual engine roughness not showing up until almost full throttle. Hopefully this helps someone else in the future.

Also, don't ban me but this was on a factory new Carbon Cub

Last edited by Narwhal : 08-10-2022 at 02:53 AM.
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  #48  
Old 08-10-2022, 10:38 PM
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skylor skylor is offline
 
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Quote:
Originally Posted by Narwhal View Post
Well, replacing the coil pack that powers the #2 and #1 top spark plugs fixed it! I'm pretty happy about that! Thanks Van's Air Force for all your help!

Before replacement, we did a "spark test" of the coils by spinning the prop slowly by hand with the spark plug wires disconnected & fuel off, but with the coils still connected to the ignition modules and the ignition systems on. All of the other coils would send an arc between the two output towers of the coil packs at the appropriate time in the firing sequence, but the upper left coil output tower for the* #1 upper plug wouldn't arc to the #2 upper plug tower, it would arc instead from the #1 upper plug output tower*to one of the bolts that holds the coil pack bracket to the airframe. Aside from that, I'm not sure what went wrong.

Also, we noticed that the coil pack for the #1 and #2 bottom plugs was arcing through the case due to a hairline crack in both tower cases, and not from the tower tips, but changing that coil pack had no effect on the problem. The problem cleared up when I changed the coil pack powering the #1 and #2 top plugs alone.

So, yeah. On a lightspeed ignition, apparently some kind of breakdown inside a coil pack can cause the tach to read 20-30% high and swing erratically +/- 300 RPM with actual engine roughness not showing up until almost full throttle. Hopefully this helps someone else in the future.

Also, don't ban me but this was on a factory new Carbon Cub
I'm glad you finally solved the problem! I suppose it's possible that the faulty coil was generating some EMI that was interfering with the tach signal.

Skylor
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