Electronic ignitions fall into two broad categories : those that work by
inductive kickback in the coil (as points do); and those that generate a
relatively high voltage then use the coil as a step-up transformer. The
first category (sometimes called point amplifiers) are, in effect, just
electronic switches that replace the function of the points. The
Pertronix, Crane XR700, and most OEM auto electronic ignitions fall into
this category. The second category (sometimes called capacitive
discharge or CDI) includes the MSD line, the Crane XR3000, and many OEM
motorcycle electronic ignitions.
This is the distinction Joe was referring to, and it's real. IMO the
big advantage of the first type is it's relative simplicity, which
should translate to lower cost and better reliability. CDIs are
considerably more complicated, but at least in theory offer faster spark
rise times (important for firing fouled plugs, hence their use in
2-cycle motorcycles), and the ability to do fancy things (like the
multiple sparks per firing of the MSD 6 series).
Randall - almost a EE, but got distracted by computers <g>
Trevor Boicey wrote:
>
> Joe Curry wrote:
>
> > However the Pertronix is not really an electronic ignition in the true
> > meaning of the term. I found out from MSD ignitions that the Pertronix
> > is simply a replacement for contact points, using a magnetic
> > switch that is actuated when one of the permanent magnets comes
> > in close proximity to the small box that fits into the distributor.
>
> That's simply not true. It's a hall effect sensor
> that is activated when that magnet goes by, but it's not just
> a switch.
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