SonexBuilders.net

Hi ya'll,

So I'm thinking ahead a bit to setting the timing on the secondary ignition. I'm still a long way from that on my plane, but I've read the aerovee assembly manual and many build logs. It seems that a fair number of folks fought high CHT problems while they iteratively made small adjustments on the secondary timing.

Has anyone ever tried just using an oscilloscope to measure the spark timing directly? It seems like doing this on the ground would be easy-cheesy if you have access to a modern digital scope. Just a loop of wire around the top and bottom plug wires of one cylinder + a capacitor and a resistor to protect the scope. Then you can see the two sparks in time and adjust (on the ground without needing long engine runs or flight) until the sparks line up. It sounds like a <15 min operation with the right setup.

Am I making some mistake here? If not, this is probably what I'll end up doing when I reach that point.

There are some good enough scopes in the $200 range but I bet most EAA clubs have at least one member with access to one (and the knowledge on how to use it).

I used a timing light to set my ignition. Running at 1500 rpm it was dialed in perfectly. At altitude I did the ignition test and shut off the mag ignition and watched the temps climb. On landing I retarded the advance and after a few trys got the cht to come into line. The timing light just does not work at the low rpm but it gets you close. An oscilloscope would probably be the same. But what the hell give it a go and report back....anything that works is a step forward!!

I just timed mine as per the AeroVee manual and it worked and works fine-I have never changed it. I get no change in RPM's on ignition check and no CHT problems. Runs great with either ignition and both.
Loren
Onex 33

Loren, just for fun try switching the electronic ignition off and run on just the mags for 20-30 min and see if you notice any CHT change. My engine would run about 10 degrees cooler on just the mags.

Thanks for the good advice. I'll report back when I try it (in twoish years ;-))

I'm a little late on this. I agree with Loren. I followed the Aerovee and Aeroinjector manual and found the entire process to be very easy to do. I have the same results.

Will try that radfordc and let you know. On another electronic issue, when I turn my prop by hand, I can hear a little click in 360 rotation. The number of clicks equals the number of magnets in the alternator stator. I also get a little electric hum at idle that goes away as soon as rpms are increased. Alternator works fine and I have a pretty good size electric load. My friend Mark (Onex 35) has the older stator that was supplied by Jabiru via Sonex (open windings) and I eneded up with a stator(encased windings) from Sonex's new supplier. Just wondering if anyone else has noticed that and what kind of windings in your stator.

Seems a while back someone else talked about hearing a "click" like that. Turned out to be loose screws allowing the stator assembly to move.

4 screws in mine and they are tight-thanks radfordc

They may well be tight because they have bottomed out in their tapped blind holes...That was the case for me
When I experienced exactly the same symptoms you have described...I had to through drill and retap the threads...Might be worth a close inspection.