Outboard Motor Coils

[Rob Skala]

> At 10:26 AM 4/11/96 -0400, you wrote:
> >While reading several recent threads regarding distributorless ignition
> >systems, I began wondering if anyone has looked into the applicability of
> >marine -- specifically, outboard motor -- ignitions for automotive use.
> >
> 
> >This engine also uses unusual spark plugs.  There are no conventional
> >electrodes.  Looking end-on to the plug, it looks like an archery target --
> >three annular rings.  The center ring is the center electrode, the second
> >ring is the insulator, and the third ring is the outer electrode (case).
> >Viewed from the side, the plug is flat across, with the insulating ring
> >slightly recessed.  The spark occurs at any point across the faces of the
> >center and outer rings.  These plugs last a long time, and, of course, there
> >is no gap to adjust.
> >
> >Question 2:  Has anyone used plugs like this, and to they have applicability
> >in an automotive application?
> >
> >I can provide make and model info if there is any interest.
> >
> >
> >Regards,
> >
> >John
> >
> ============================================================================
> 
Hi There,

I just thought I would put my little bit of knowledge in here about the 
spark plugs you mentioned. They sound very similar to the NGK plugs that 
are used by MAZDA in some of their rotary engines. They are a surface 
discharge plug that performs very well, especially in turbo-charged rotarys.
The plugs used in the rotaries are SD-10 and SD-9 both made by NGK. 

A while ago I was looking through the NGK catalouge and found that there 
is quite a variety of heat ranges available in these types of plugs. The 
usual designation is SD-xx where xx refers to the heat range.

Hopefully this is of some use to the fellow list members !!!

Regards,

Rob Skala



Robert D Skala
Materials Research Group
School of Physical Science
Curtin University of Technology
GPO Box U1987
Perth	6001
WESTERN AUSTRALIA
Telephone: +61 9 351 2331
Fax:	   +61 9 351 2377
email: skala_rd at cc.curtin.edu.au