Boxerworks.com

Ive installed a capacitor discharge ignition ( cdi ) system on my 1979 r65 .
The system is simply switchable back to points whilst riding ( I never rely on transistors ) .
The Question is am I right in feeling a difference in power and response from one system to the other ?
The main difference is that the cdi power is a lot less than the points and coil power when
calculating the electrical discharge energy . I always thought a spark was a spark and an
explosion would be the same ! .
In the old days ,here in England, some spark plugs were called "spitfire jet igniters " with three spark gaps....
promising better everything . Any truth in these thoughts ?
JIM

the real advantage of multi prong plugs is reliability, only one prong fires at a time, but when one fowls out you you have 2 more to carry on. This is a simple version of what a Stitt co rep tolds us at a tech session one time. I use 4 prong RM77 Champion plugs at work.

what color is your spark? Does the bike miss when on the CDI side? unless your cdi is weak I wouldn't think one system would have more power than the other. maybe one of the Sparky type will chime in.

My view is that it is energy that ignites the fuel mixture. Even if all three prongs on that three prong spark plug arced at the same time, the energy expended would be the same as one prong.

Spark plug "breakthroughs" have been a favorite to attract customers. I remember, decades ago, when the JC Whitney catalog had a full page ad every issue saying, "Throw away your spark plugs! Replace them with Fire Injectors!"

Those fire injectors looked suspiciously like today's 3 prong spark plugs.


Ken

My Grandfather had a BMC garage in the 30's, and one day Esso sent him a box of their fancy monogrammed pencils.
Being a canny Yorkshireman, he put them to good use.
Cars used to have a lot of plug trouble in those days, and would often pull in with a misfire, whereupon, he would clean the plugs (probably a quick wipe on the overalls), produce a pencil, and scrat some graphite onto the electrodes.
When the engine burst into enthusiastic life, he would sell the impressed motorist the "special" Esso pencil for an exorbitant sum.
In later life, he did a lot of charity work -- conscience perhaps ...?

Sunbeem.

Hey Sunbeem - don't knock pencils.
They are the airheads of penmanship.
They write on anything, and work below freezing (no antifreeze).
You don't see carpenters with a pen tucked behind their ear.
Carry a pencil in your toolbox, it will work 20 years from now.
(Oh yeah - you can also clean sparkplugs with them.)

dougie wrote:Hey Sunbeem - don't knock pencils.
They are the airheads of penmanship.
They write on anything, and work below freezing (no antifreeze).
You don't see carpenters with a pen tucked behind their ear.
Carry a pencil in your toolbox, it will work 20 years from now.
(Oh yeah - you can also clean sparkplugs with them.)

And write yourself a note to get some spare plugs.

OK you two, but I've yet to find one that can spell.

Sunbeem.

Pencils are also very good at sabotaging a mate's bike ....just a little graphite track down the outside of the plug ............

dougie wrote:Hey Sunbeem - don't knock pencils.
They are the airheads of penmanship.
They write on anything, and work below freezing (no antifreeze).
You don't see carpenters with a pen tucked behind their ear.
Carry a pencil in your toolbox, it will work 20 years from now.
(Oh yeah - you can also clean sparkplugs with them.)

And... they write upside down...

Took several Billion Dollars and a lot of dangerous hard work to produce a pen that would do the same...



Rob

The principal difference between Capacitive Discharge Ignition (CDI) and Inductive (Kettering) type ignition is that CDI tends to produce a very hot but short spark while Inductive systems tend to produce a cooler but much longer spark. Each type has advantages. The very hot short CDI spark is good at punching through spark plug fouling while the longer fatter spark from the inductive system will be better at igniting mixtures that might not be absolutely right. In short, if everything else is 'right' you'll see not a lot of difference.

Of course, this assumes a simple CDI system and a basic inductive system. There are tweaked systems on both sides that seek to close the gap. Multi spark CDI systems address the short duration of CDI sparks. Most properly designed electronically switched inductive systems have a much hotter spark than points switched systems. There is probably little benefit to be gained from switching a Kettering system for a CDI system (and Vice Versa of course).

Rob