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Thread: compression test

  1. #21
    Senior Member Dan L's Avatar
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    Default Re: compression test

    I did a compression test this week on the O-340 while I had the cowl off for other reasons. Two 78s a 77 and a 76.

    One thing I did was add a keeper for attaching safety wire to the quick drain on the oil sump. There never was an attach point on the sump (maybe there is now?). This is a simple formed U channel with an .812Ē dia. Hole in the middle. There are two flats on the sump boss and the U touches these and canít rotate.

    A481EDAB-EB4D-4D1C-960E-99080DFB7995.jpg
    Flying Carbon Cub EX #11 since 2011

  2. #22
    Senior Member Dan L's Avatar
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    Default Re: compression test

    IMG_8188.jpg

    I was noticing an occasional miss on recent flights that seemed to be an ignition issue. My first thought was it was similar to the time I needed to change out the timed-out spark plug leads. So I pulled the cowl and found that the rear connector (yellow) coming off the coil was both loose and looked black like there had been some arcing. I cleaned it up with electrical cleaner (prior to this picture) and pinched the connector to make a tighter connection. (918 hours on this O-340)

    There were no more misses on a test flight the same day.

    It had always seemed to me that these connectors were the weak link in the Lightspeed ignition train. Compare these to magnetos and the leads that are threaded onto traditional massive-type plugs..........
    Flying Carbon Cub EX #11 since 2011

  3. #23
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    Default Re: compression test

    RIGHT!. I have had several issues with these connectors as well and would like to find an alternative. In addition to the spade connectors coming loose, the positive one (BLUE) that attached to the center conductor of the lead will break the wire very easily as that wire is braided but very very thin. It doesnít take much vibration to get a break, even when using shrink tubing over the connection.

    Quote Originally Posted by Dan L View Post
    IMG_8188.jpg

    I was noticing an occasional miss on recent flights that seemed to be an ignition issue. My first thought was it was similar to the time I needed to change out the timed-out spark plug leads. So I pulled the cowl and found that the rear connector (yellow) coming off the coil was both loose and looked black like there had been some arcing. I cleaned it up with electrical cleaner (prior to this picture) and pinched the connector to make a tighter connection. (918 hours on this O-340)

    There were no more misses on a test flight the same day.

    It had always seemed to me that these connectors were the weak link in the Lightspeed ignition train. Compare these to magnetos and the leads that are threaded onto traditional massive-type plugs..........
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

  4. #24
    Senior Member Dan L's Avatar
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    Default Re: compression test

    Quote Originally Posted by Dan L View Post
    IMG_8188.jpg

    I was noticing an occasional miss on recent flights that seemed to be an ignition issue. My first thought was it was similar to the time I needed to change out the timed-out spark plug leads. So I pulled the cowl and found that the rear connector (yellow) coming off the coil was both loose and looked black like there had been some arcing. I cleaned it up with electrical cleaner (prior to this picture) and pinched the connector to make a tighter connection. (918 hours on this O-340)

    There were no more misses on a test flight the same day.

    It had always seemed to me that these connectors were the weak link in the Lightspeed ignition train. Compare these to magnetos and the leads that are threaded onto traditional massive-type plugs..........
    I was poking around on the CC site and found there is a Service Letter on this very issue from May of 2020.
    http://cubcrafters.com/c/wp-content/...connectors.pdf

    It would be nice if CC would let owners know about these things. It seems like at one time there was an email sent out but I havenít seen anything about issues like this in years.
    Last edited by Dan L; 07-16-2020 at 12:21 PM.
    Flying Carbon Cub EX #11 since 2011

  5. #25
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    Default Re: compression test

    Yep....I never heard of it either. This Service Letter isnít saying to do anything different than the original build but just an inspection of it. Like I said, I think the positive lead needs reinforcement of some sort because of how thin that center conductor wire is. I took a large tie wrap and cut a short piece (maybe 1/2Ē) and put a piece on either side of where the wire crimps onto the connector like a ďsplintĒ and then shrink wrapped around that to hold it on. I think this will keep it from flexing and breaking that wire. I think perhaps a short piece of tubing just a bit larger than the wire that goes over that connection would work even better. I think that is the weak link to this entire connection........that wire is so thin.

    I actually carry extra crimp connectors in the plane. Itís usually pretty easy to see when one is bad on run-up (or in flight mag check). Put up the engine data page on the G3X with mags on BOTH. When you turn mag to L or R, watch the EGTís. If one of these connectors is broken or has a bad connection, you will see that EGT for that cylinder immediately drop off (the same thing will happen if you have a bad plug).

    If you have the diagram of the wire routing, you can see if itís the top or bottom cylinder. If the EGTís drop on the LEFT ignition, then itís the TOP of the cylinder plug or coil and if RIGHT it on the bottom.

    I attached a drawing photo you can put on your phone and have it handled if needed.

    3F6E6197-70D2-4896-8AD0-A1D68118B242.jpg

    Quote Originally Posted by Dan L View Post
    I was poking around on the CC site and found there is a Service Letter on this very issue from May of 2020.
    http://cubcrafters.com/c/wp-content/...connectors.pdf

    It would be nice if CC would let owners know about these things. It seems like at one time there was an email sent out but I havenít seen anything about issues like this in years.
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

  6. #26
    Senior Member Dan L's Avatar
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    Default Re: compression test

    It always seemed to me that this would be a good application for a BNC type connector.
    Flying Carbon Cub EX #11 since 2011

  7. #27
    Senior Member Springloaded's Avatar
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    Default Re: compression test

    Quote Originally Posted by Dan L View Post
    It always seemed to me that this would be a good application for a BNC type connector.
    How many hours you have on that bird now Dan?
    Last edited by Springloaded; 07-19-2020 at 05:01 AM.
    Chuck Kinberger
    Southern Cubs
    Florida Cubcrafter Sales
    Jupiter Fl.
    Pa11890ck@gmail.com
    You can sit at home & hear the News or get out there & be the News

  8. #28
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    Default Re: compression test

    Yes but i guess the coils are the weak link since they have the spade connectors on them??? Maybe hard wire/solder larger wires from pos and neg spade connectors to bnc and then bnc on coax from ignition box? Cubcrafters.......will this work?

    letís see if anyone is watching......

    Quote Originally Posted by Dan L View Post
    It always seemed to me that this would be a good application for a BNC type connector.
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

  9. #29
    Senior Member Dan L's Avatar
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    Default Re: compression test

    Quote Originally Posted by Daveembry View Post
    Yes but i guess the coils are the weak link since they have the spade connectors on them??? Maybe hard wire/solder larger wires from pos and neg spade connectors to bnc and then bnc on coax from ignition box? Cubcrafters.......will this work?

    letís see if anyone is watching......
    I agree that the spades out of the coil then become the weak link. Iíve though about doing what you describe. - soldering on a male BNC. But a flexible wire should probably be wired between the spade and male BNC. The best solution IMO would be a redesign of the coil with the BNC coming directly out of it.

    Chuck there are 918 hours on this EX.
    Flying Carbon Cub EX #11 since 2011

  10. #30
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    Default Re: compression test

    I was sort of an early adopter of Lightspeed on my RV8 in 2004. From talking to other people and Klaus I came to the conclusion that the system is very reliable if you go totally overboard on supporting all the wires. I finally put 700 hours on the RV without problems, and got great performance from the ignition system. I am looking forward to having it on my EX-3.

    John

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