In article ,
Karl Townsend wrote:

On Thu, 17 May 2012 22:33:46 -0400, Spehro Pefhany
wrote:

On Thu, 17 May 2012 11:59:41 -0500, the renowned Karl Townsend
wrote:




P.S. Extra bonus question, any way to just figure what the old ones
had for a filter?

Karl

I'm not sure why a filter would be required- looks like you could
reduce the sensitivity using shielded wire and maybe a single turn
around the ignition wire. No?


Best regards,
Spehro Pefhany

I'm going to play more with this idea. the vendor had me cut the lead
down to one inch and use just a hook, no joy. I think I'll try to
increase the distance by wrapping a gob of elctrical tape around the
plug wire.

I assume you're thinking AL foil. Which wire would you wrap, plug wire
or unit pickup lead, and should it be grounded?

A classic dodge would be to pass the sparkplug wire through the center
of a ferrite toroid upon which a few hundred turns of fine wire had been
wound, forming a simple current transformer. The fine-wire winding
would be connected to a bit of coax which would carry the signal to the
tach. The winding can be shielded (so long as the shielding does not
form a closed metallic loop).

This will sense the current drawn by the spark, not the spark voltage.

Joe Gwinn