Another use for a waste (maverick) spark coil??

[John Dammeyer]

Don't know how you'd wire it up exactly.  I knopw SAAB in their newer
cars no longer uses a CAM sensor but uses the spark plug coil to
determine which cylinder fired.  As far as I know it works like this.
As the engien starts to crank they fire each plug at TDC (2 at a time
like waste spark but with single coils).  After they fire the plug they
put about 400V across the plug and measure the current.  The one which
is burning conducts and therefore was at TDC of the compression stroke.
That means in 1/2 to one turn of the engine by the starter you know
where you are and after that can time off the crank.  Really clever but
requires a custom coil per cylinder.  I'd love to see a schematic.

John Dammeyer


> -----Original Message-----
> From: owner-diy_efi at diy-efi.org 
> [mailto:owner-diy_efi at diy-efi.org] On Behalf Of Greg Hermann
> Sent: Thursday, July 12, 2001 6:54 AM
> To: diy_efi at diy-efi.org
> Subject: Another use for a waste (maverick) spark coil??
> 
> 
> 
> >>I've never been able to measure the open circuit
> >>voltage on the output but obviously the turns ratio
> >>on the coil determines >that ultimately.
> >
> >I use an old TV HV probe, modified with a BNC
> >connector, and a flying lead with a ground clip. Hooks
> >right onto my O-scope.
> >
> >Lot's of interesting things can be observed.
> >
> >Disconnect one of the plug leads on a waste spark
> >setup, watch what happens to the other side.
> >
> >Carter
> >
> Which leads me to wonder--
> 
> Hmmmm!!??!!
> 
> I wonder whether using a two lead (waste spark) coil, but not 
> in the usual waste spark manner (only firing one plug) might 
> be an excellent beginning for an ION measuring device??
> 
> Greg
> 
> 
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