Cap discharge

[William Boulton]

Mark,

In July of 1975, Electronics Australia magazine did project for a CDI. I
purchased a kit a couple of years later from Dick Smith Electronics and
have been using it ever since (not 1 vehicle). I'll give you the details
and you may be able to (at least) get a copy of the original documentation
from DSE even though the kit has not been current for a number of years.

    Kit #:  K-3280

    Snail Mail Addr:    Dick Smith Electronics
                        PO Box 321
                        North Ryde
                        NSW     2113
                        Australia

The original documentation did not describe how to wind the transformer
since it came pre-wound in the kit. If they can't help you, the only other
course open would be to get a copy of the project article from EA at about
A$7.50. Their address (snail mail) is;

                        The Secretary
                        Electronics Australia
                        PO Box 199
                        Alexandria
                        NSW     2015
                        Australia

Some points I have learned about CDI systems.

    1   They don't like lean mixtures. Spark duration too short.

    2   They work much better in combustion chambers with good swirl &
        distribution. My unit was quite remarkable on a '77 Honda Civic
        but very ho-hum on a '78 2850 Torana (sorta like 3.? litre Chev 6
        of the same period).

    3   Slight misfire at very light throttle (slight over run). Don't
        know why but I've seen it on other units too.

    4   Great cold starting. 400v on the primary will start anything.

    5   They will reliably fire the worst fouled plugs you will ever see.
        I had one plug so fouled I couldn't dig the crap out and it kept
        on firing.

    6   Great on engine that rev like stink. No HEI coil will saturate in
        under 3 ms while a CDI will charge its capacitor to 400v in far
        less time and they draw stuff all current. That's why some small
        bike engines use them as do the OZ 5l Group-A cars. So do Mercury
        outboards.

Thats it, bye

Bill Boulton




On Mon, 14 Oct 1996, Mark Pitts wrote:

> Any body know where to start looking for a cap discharge schematic, or any other info for that matter.
> 
> Mark
> 
>