ION-related IGN Comments & Coil Quest

[Shannen Durphey]

steve ravet wrote:
> 
> kenkelly at lucent.com wrote:
> >
> > garfield at pilgrimhouse.com wrote:
> > >
> > > On Wed, 27 May 1998 20:25:43 -0400, "Bruce Plecan" <nacelp at bright.net>
> > > wrote:
> > >
> > > >All the General Motors Distributorless Coils are four terminal.
> >
> > GM HEI coils are also four terminal, so we can probably say
> > that all GM coils since 1975 are transformers, not
> > autotransformers. The HEI coils have all four terminals
> > already in place, of course it implies using the HEI
> > distributer for easy mounting.
> >
> >                 Ken
> 
> How about a five terminal coil?  I just looked at my motor (from a '91 Caprice, TBI 350), and it has the small cap HEI w/external coil.  The coil has 4 regular wires (two white, one pink, one large
> gauge pink) on two weatherpak plugs, plus the high tension lead to the distributor.  What's up with that?
> 
> As far as coil-per-plug, I had compiled a list of them at one time on the EFI reference document I was maintaining.  You can find a copy of it on the vettenet, http://www.vettenet.org/efi_ref.txt
> 
> --steve
> 
> --
> Steve Ravet
> steve at imes.com
> International Meta Systems
> www.imes.com

Okay.  Here's what you got from the GM HEI coils. The IN CAP
style have 5 wire terminals .  The BAT and C+ are connected
to the primary positive side.  BAT is power in, C+ carries
voltage to the module.  TACH and C- are connected to the
primary negative side, and C- is switched by the module. 
GND is connected to the iron frame of the coil and is the
ground for the secondary.  Spark, of course, travels through
the exposed metal portion which aligns with the carbon brush
in the center of the cap.  

EXTERNAL style coils are very similar.  There are two
connectors, each with two wires. In each connector one wire
is pink and one is white.  Although they are not labeled,
the  wires in the grey connector are BAT (large pink) and
TACH(small, white, and often terminates close to the coil,
taped back to the harness).  The wires in the black
connector are C+(pink) and C-(white) and are part of a small
harness which connects to the ignition module.  The design
and function of these is similar to the above description. 
There is no GND wire as the coil is bolted directly to the
manifold.

Although they are probably difficult to find in the wrecking
yards, the coils for the newer Vortec pickups and (if my
memory is correct) LT1 type engines are electrically
similar, but physically smaller.  The secondary terminal is
somewhat recessed, and provides better coil wire retention. 
Wire colors are different (and much smaller gauge, a sign of
what?), but same function.

And now a brief question, found only by those who bother to
read an entire post.  Will someone please give me a brief
description of the difference between a transformer and an
autotransformer?  (We could say that all transformers in
cars are Auto transformers ; )

Shannen