Scota4570

I have an idea for a mechanical advance I would like to try to make.

I am not understanding which way the advance goes. One times an electronic ignition at about 30 BTDC static.

So now I run the engine. I flip the prop and it fires at 30 btdc? It then advances to TDC as I rev up the engine?

Or, does the 30 represent the the most advance and it fires at about zero when the engine first starts and the ignition module senses the motion? Then I rev it up and it moves the timing to 30 BTDC?

Lnewqban

Any mechanical spark advancing mechanism allows the spark to occur sooner (relative to crankshaft degrees) as RPM increase.

Check this article out:

http://en.wikipedia.org/wiki/Ignition_timing

Aussie Maddog

My Feedback: (16)

Yes 30 BTDC is the most. Start at 6-8 BTDC.

Scota4570

Ok, that is what I meant. I would want it to fire at 6-8 BTDC at idle and advance to 30 at full rpm.

Aussie Maddog

My Feedback: (16)

correct. Generally full advance is at around 4000 RPM.

azalner

My Feedback: (8)

This is a mechanical advance I did about 20 years ago. It is an Al Diem conversion. Just for information, you might glean an idea or two.

AlZ

tkg

My Feedback: (1)

Perfect timing for most engines. 6 deg BTDC at idle and 30 degrees BTDC at full throttle. IN reality 4-8 at idle and 28-30 at WOT. If you have to chose which end of throttle to have the timing correct at chose WOT and live with what ever idle is.

Scota4570

Nice work on the OS. My thought is a new "flywheel" of absolute minimal mass. Use neodium magnents to induce the spark. The advance would be centrifugal. If I can make it come together as i visualize it is would be lighter than a CDI and retain the advance feature. Since many smaller engines need a starter anyway there would be no trade off.

gr8flyer55

TKG, is there a way to repair a synchro spark that is giving double sparks and misfiring? I think it got smacked in a mishap at our field, and was given to me by a friend.

John