[Healeys] Lucas - Judson EI ??

Richard Ewald richard.ewald at gmail.com
Wed May 12 21:14:23 MDT 2010


Actually if you think about it, all points equipped systems use the points
as a switch that turns the coil on and off.  The difference is that in a
traditional points system the points are switching a bunch of amperage (6
amps comes to mind, but my memory could be failing).  Switching this high
current caused points to pit and wear out.  In an effort to make points
systems more reliable, first came transistorized ignition systems which used
the points at a very low voltage and amperage to switch a transistor, which
then switched a power transistor to turn the coil on and off.  With these
systems point arcing is eliminated.  Assuming the rubbing block stays lubed,
the points will last many many times longer than the a traditional system.
A capacitive discharge system or CD as they were known adds a big capacitor
to the system to kick the power out of the coil up to either a higher
voltage, or a longer spark duration.  Still the points act as a switch to
turn a transistor on and off.
So what is this Judson unit?
Beats the crap out of me.  I do not believe it is a capacitive discharge
system for a couple of reasons.
1. Look at the wiring schematic  The wire from the coil is still going to
the points  The points are switching the current from the coil.  Not like
any transistorized system I ever saw.  Not like any CD system I ever saw.
2.  the name See-dee.  Sounds like CD but note the spelling is different.
Back in the day everyone called them CD systems and when written it was
always CD.  Never see-dee.
I'm thinking that this is just one more item in a long line of snake oil
that has been sold to car owners under the guise of more performance, better
gas mileage, lower emissions.
Rick


On Tue, May 11, 2010 at 9:31 PM, Alan Seigrist <healey.nut at gmail.com> wrote:

> So basically, the distributor becomes some sort of switching mechanism.  I
> suppose the advantage is the points don't get burned and thus timing
> advance
> remains constant.
>
> Alan
>
> '52 A90
> '53 BN1
> '59 Jag Mk IX
> '64 BJ8


More information about the Healeys mailing list