Looking for Capacitive Discharge Ignition systems FAQ's, etc.

"Mike Rocket J. Squirrel Elliott"

You can do a search on Megasquirt which combines the injection ECU and now the ignition ECU. Megasquirt is a DIY type of system.

I use a Crane HI-6R in my race car, the "multi-spark" only really occurs at low RPM, not at WOT (features rev limiters, retard on boost, etc..) another CDI system is the MSD ignition system.

Unless you are racing or making serious amounts of horsepower, it isn't necessary. However, if you want reliability, you can convert your application to injection (using throttle bodies) and use the Megasquirt and crank trigger ignition and you'll have a sweet system.

See "CD-Ignition-Basic.pdf" on the S.E.D/Schematic Page of my website.

This represents the fundamentals of an ignition system I designed for Ford in the early '70's, but they fretted over its cost and short spark duration. I even designed a version with multiple-sparks per firing... they still didn't like it. Ran just fine on several cars here in AZ.

I don't have the current sensing circuitry in CAD. If I can find my pencil drawings I'll post additional information.

...Jim Thompson

See the pages at:

Cost must be in the current-sense part, because one BJT, one coil, one cap and three diodes is pretty minimal. Thanks for the post, Jim.

Thanks, Dave -- good stuff.

Car companies fret over $1.50 :-(

(The BJT does have to have a BVCEO >> 350V, resulting in lousy beta back in those days. Today there's probably a power MOSFET that will do the job nicely.)

...Jim Thompson