Don Foreman wrote:

This gives enough spark under compression?

Until now, yes. :-)
There are several factors for a spark to initially jump:
* compression
* condition of spark plug electrodes
* ratio of the mixture (rich, lean; a lean one needs higher voltage)
* dU/dT of the voltage
* and of course the voltage (having 8 kV with this coil, limited by the
protection on the primary)

I have tested this one with an engine that has quite a low CR, but a spark
plug that is oiled beyond belief.

Don't forget that I do have 500 V on the primary side and a dU/dT at the
primary that is by magnitudes higher than required (forgot the numbers I
once calculated), and also higher than a conventional system. It more
resembles a CDI (but it ain't).

The energy stored is 50 mJ (cars do have something at 120 mJ to 180 mJ). But
literature says that 0.5 ... 10 mJ are enough to ignite the mixture. I'll
try that as soon as everything is up and running.

Spark duration was measured to be about 4µs with a clean spark plug. A oily
one will dramatically reduce the duration.


Nick
--
The lowcost-DRO:
http://www.yadro.de