Set timing

[JerryCPP]

I had a great article saved regarding setting the secondary ignition timing, but, like so many things, I can't find it now that I need it. I get a slight RPM increase when I shut off the secondary at full throttle. I can't remember if I need to advance or retard it. Help!

[radfordc]

Not sure what article you are referring to, but there is some discussion of setting timing here on this forum: viewtopic.php?f=7&t=661

I'm not sure if you need to retard or advance the timing, but it would be safer to retard it first and see what effect it has. You may be surprised at how little change of the secondary timing is needed to get it exactly right.

Watching my engine I've found that it runs coolest and best in flight with the secondary ignition shut off. I suspect that it has something to do with the location of the secondary sparkplugs in the combustion chamber...but that's only a guess. Maybe the guys in Wolfsburg got it exactly right back in the 1930's?

[billmaxmcw]

This worked for me: Running on the primary (magneto) vs. secondary ignitions (only) should not vary in RPMs at cruise. If the secondary runs faster, it is too far advanced. If the secondary runs slower, it is too far retarded.
Bill

[dallen]

I remember reading on the old form a way to set the secondary timing using a timing light. Can anyone explain how to do that?

[SonexN76ET]

I found a neat trick to help you set your timing. First, please follow the AeroVee manual to determine if your timing needs to be advanced or retarded. I found that in flight my engine RPMs increased if I turned off the secondary ignition. Sonex tech support told me that likely that was due to the secondary ignition being too far advanced. Early on in my test flights I retarded the secondary ignition and my RPM and power really picked up. After 17 hours of flying, the engine seemed to have lost power once again so I tested the secondary ignition in flight and again the RPM increased with the secondary ignition off. Apparently, I had not tightened the trigger magnet cap screw tight enough and it had slowly advanced or I did not have it far enough retarded on my earlier try. After a few attempts at adjusting it, it is right on now.

Once you make this determination of whether the secondary ignition is too far advanced or retarded, it can be a challenge to figure out how far to advance or retard the secondary ignition. I have a hard time lining up the little dot/line with the contour pointer on the secondary ignition module when looking at it from an angle as you need to do with the engine mounted. What worked for me was putting a piece of masking tape on the trigger and a piece right next to it on the cover of the alternator, then using a fine tip sharpie to draw a reference point on both pieces of tape that line up with once another. That way when you unscrew the trigger cap screw and the trigger turns, you can realign it where it was when the cap screw was tight. You can then make incremental adjustments to your timing. I kept my trigger rotations to less than a 1/16 of an inch for each attempt. You will have to take the tape off each time before you start the engine and put new tape on with each adjustment. The key here is that it lets you know how much you are actually moving the trigger with each attempt. I did ground runs as Sonex documents in the Aerovee manual to check the timing prior to doing any in flight checks.

Also, I do not know of anyone who has had any real luck using a timing light. A timing light might help you get the timing right on the ground, but will do nothing for your in flight timing. Plus, it is dangerous in the close confines of the Sonex engine area and propeller.

Anyway, I hope this tip helps!