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Thread: Timing the Carbon Cub

  1. #1
    Senior Member turbopilot's Avatar
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    Default Timing the Carbon Cub

    I was changing the oil on my Carbon Cub so I thought I would also check the timing. So I consulted the CC11-160 Maintenance Manual for some step by step illustrated instructions about doing timing with an electronic ignition. No joy there instead it referred to the Light Speed Engineering Installation and Operation Manual. A little more information there but none of it specific to the Carbon Cub installation.

    I got a timing light and was about to give it a try when I discovered it is not a one man job. The plenum will not allow you to see the timing marks from the cockpit with the engine running.

    Here are the timing marks on my Carbon Cub. Can someone walk us through checking and adjusting timing on the Carbon Cub? Would be helpful to know which way to slide the timing adjustment to change timing if it is needed. Thanks.



    Bob Anderson, CC11-00435, N94RA

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    Member TheCubWorks's Avatar
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    Default Re: Timing the Carbon Cub

    That circuit board that is bolted to the front of the engine case is the crank sensor. You will find that the parallax you look at the timing will be way farther off than the true timing. For example LOOK at the Angle you took the picture. NOTE the white triangle that points at the split line of the engine, and how this looks off slightly. this is how you time the engine. the variable nature of the ignition timing makes testing them (for lack of better words) random when checked with the strobe light.

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    Administrator Pete D's Avatar
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    Default Re: Timing the Carbon Cub

    The beauty of the Light Speed ignition system is that there are no moving parts. Once the timing is set, there is nothing that is moving, so nothing wears and the timing never needs to be adjusted.

    Ignition system maintenance is basically reduced to cleaning/gapping/replacing the spark plugs as needed. Inspect the leads for chaffing, but if they are routed and secured properly they will last the life of the engine.

    LSE recommends gapping the plugs every 100 hours. If you are paying a shop to do that, the cost of the plugs is so minimal that (with the standard plugs anyway) it is more economical to just remove and replace rather than paying shop time to have a $3 plug cleaned and re-gapped.

    Pete D

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    Senior Member turbopilot's Avatar
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    Default Re: Timing the Carbon Cub

    Quote Originally Posted by Pete D View Post
    The beauty of the Light Speed ignition system is that there are no moving parts. Once the timing is set, there is nothing that is moving, so nothing wears and the timing never needs to be adjusted.

    Pete D
    Understand, I just wanted to check that it was set correctly.

    So do you time the front cylinders to the "21" mark and the back cylinders to the "201" mark? I assume the "40" mark and "220" marks are the timing marks when manifold pressure is connected. Can you confirm?

    Also the Light Speed Manual suggests for engines with compression ratios above 8.7:1 that timing be retarded another 5 degrees using 35 degrees with MP hose connected and 16 degrees when disconnected. Since the CC340 has a compression ratio of 8.9:1 why is the timing set at 40 degrees versus 35 degrees?
    Last edited by turbopilot; 10-17-2010 at 10:06 PM.
    Bob Anderson, CC11-00435, N94RA

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    Member TheCubWorks's Avatar
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    Default Re: Timing the Carbon Cub

    Bob,

    The other 99% of Light Speed owners have to install the LSE them selves. therefore they generally use the sensor that goes in the mag drive hole. this unit is affected by ignition creep because there is LOTS of moving parts involved. When CC and ECI test the engine with the LSE at 40 the engine can take it, Light Speed is not going to tell anyone to do something a that could come back on Light Speed.

    The ignition event for the front cylinders will be 180 degrees in rotation different than the rear cylinders.
    Both front cyclders spark at the same time, one on the power stroke and the other on the exhaust stroke. This is a wasted spark system and it cleans the plugs, and wears them out twice as fast.

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    Senior Member RanRan's Avatar
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    Default Re: Timing the Carbon Cub

    Quote Originally Posted by turbopilot View Post
    Understand, I just wanted to check that it was set correctly.

    So do you time the front cylinders to the "21" mark and the back cylinders to the "201" mark? I assume the "40" mark and "220" marks are the timing marks when manifold pressure is connected. Can you confirm?

    Also the Light Speed Manual suggests for engines with compression ratios above 8.7:1 that timing be retarded another 5 degrees using 35 degrees with MP hose connected and 16 degrees when disconnected. Since the CC340 has a compression ratio of 8.9:1 why is the timing set at 40 degrees versus 35 degrees?
    The smaller number is the important one, since advancing too far can lead to pinging, detonation and stressing out connecting rods and bearings. The rule of thumb is to advance the timing until the engine speeds up and then back it off a bit. That's the sweet spot. That spot is going to change slightly if you switch between Mogas and Avgas.

    If you do switch fuels, then you need to retard for the worst case - which is, no doubt, how the engine is initially set-up.
    Last edited by RanRan; 10-18-2010 at 08:56 AM.

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    Senior Member turbopilot's Avatar
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    Default Re: Timing the Carbon Cub

    Quote Originally Posted by RanRan View Post
    The smaller number is the important one...
    I would agree in a world of magnetos but I am not sure in the world of variable timing electronic ignitions.

    First I am brand new to the world of electronic ignitions in airplanes. The Carbon Cub is the first one I have owned, so I am just trying to understand what is going on. The reason I am thinking about this area relates to my summer of evaluating CHT's in the Stroker 340. I have had a great deal of experience optimizing fixed timing in magneto driven aircraft to lower CHT's, so I am wondering how much influence the variable electronic timing in the Stroker 340 may have on CHT's.

    Here is how I understand the Light Speed system works from the documentation. Please correct me if I don't have it straight. The Plasma CD Ignition apparently has the capability to cover a 19 degree range of timing. The Plasma system uses RPM and manifold pressure as the variables to compute the actual timing pulse which begins at the retarded end of the 19 degree range and advances to the other end of the range depending on RPM and MP. The system will start the engine at top dead center with ambient manifold pressure and no RPM detected, then move to the retarded end of the 19 degree range at idle.

    So in the Carbon Cub it appears (based on the timing marks) that the 19 degree timing range is set up to begin at 40 BTDC at idle then advance to 21 BTDC depending on RPM and MP. Correct?

    What is not published is the actual algorithm that determines what the timing may be at any given RPM and MP. Quite possibly this is considered proprietary information by Light Speed Engineering. So while we are flying along at a specific power setting we don't know what the actual timing is in the engine. Light Speed does sell an indicator to display this information.

    Since it appears the timing algorithm is not adjustable it really does not matter what the number may be for any specific power setting since the algorithm apparently can't be changed. What can be changed is the beginning and the end of the 19 degree timing range.

    So all this is my long winded way of asking the question is the setting of the 19 degree timing range optimal in the Stroker 340? Based on the Light Speed Engineering documentation recommendations on cylinder compression ratio and timing, it would appear the timing should be advanced another 5 degrees. A 5 degree change in over all timing should lower CHT's significantly all other things being equal (which is not a sure bet).
    Bob Anderson, CC11-00435, N94RA

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    Administrator Pete D's Avatar
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    Default Re: Timing the Carbon Cub

    We use the procedures in section 3.2 of the LSE manual found here:

    http://www.lightspeedengineering.com...II_II+_III.htm

    It sounds like you have a pretty good handle on how the system works.

    You can actually hear the system shift the timing right after startup-the engine smooths out several seconds after startup like a switch was flicked.




    Pete D.

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    Member TheCubWorks's Avatar
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    Default Re: Timing the Carbon Cub

    Quote Originally Posted by turbopilot View Post

    So in the Carbon Cub it appears (based on the timing marks) that the 19 degree timing range is set up to begin at 40 BTDC at idle then advance to 21 BTDC depending on RPM and MP. Correct?
    I think you are getting somewhere. respectfully, and for you knowledge, when we advance timing the ignition event happens, in this case, closer to the 40 BTDC and retard is closer to the a 21 BTDC. you are just backwards in the above statement. it begins at 21 BTDC and advances to 41 BTDC.




    [/QUOTE]So all this is my long winded way of asking the question is the setting of the 19 degree timing range optimal in the Stroker 340? Based on the Light Speed Engineering documentation recommendations on cylinder compression ratio and timing, it would appear the timing should be advanced another 5 degrees. A 5 degree change in over all timing should lower CHT's significantly all other things being equal (which is not a sure bet).[/QUOTE]

    Yes this would help, but you may be surprised how little.

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    Senior Member RanRan's Avatar
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    Default Re: Timing the Carbon Cub

    Quote Originally Posted by turbopilot View Post
    What is not published is the actual algorithm that determines what the timing may be at any given RPM and MP. Quite possibly this is considered proprietary information by Light Speed Engineering. So while we are flying along at a specific power setting we don't know what the actual timing is in the engine. Light Speed does sell an indicator to display this information.
    The actual algorithm is going be a very steep curve. One of the main reasons for automatically retarding the timing is to help the engine idle smoothly at low MP. But beyond the idle, the power curve is dependent on fuel-air flow. I would bet that the timing jumps to the full advanced number very quickly from idle RPMs and then stays there. That would be easy to confirm with a strobe light.
    Last edited by RanRan; 10-18-2010 at 02:34 PM.

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