ignition question - what would keep a coil from..., being used with a CDI Options

[Aaron Cox]

as long as the ohmage is within the range, what would make a coil company say its not for use with a capacitive discharge ignition??

your thoughts?

BTW - coil is a pertronix flame thrower 1.5 ohm.

[ArtechnikA]

because a "coil" is used with a Kettering battery-condenser ignition as an energy storage device. a BIG part of its functionality is that it builds an electromagnetic field and has a big core to act as an every storage device. it charges while the points are closed, and then, when the points open and the electromagnet stops being a magnet, the collapsing electrical field is multiplied by the secondary windings to create the high voltage spark.

while there's crossover - some devices do both jobs marginally well - a CDI "coil" is not a coil -- it is a pulse transformer. it doesn't have to have a big iron core to act as a storage device. it's JUST a transformer.

so there's a whole lot more to the story than the resistance of the primary winding.

a "coil" is designed to work on 12 volts - it's charged from battery current. a pulse transformer is typically fed high-inrush currents at 300 VDC or better. coils designed to work on 12V (insulation comes to mind...) are not designed to have big pulses at 300V dumped in in a hurry.

it might work for a while - until the smoke comes out...

[Aaron Cox]

people run their Bosch Blue coils with mallory CDI's all the time. why cant i run a hotter coil with the CDI?? without buying the CDI 'pulse transformer' which they still call a coil...??

[ArtechnikA]

QUOTE (Aaron Cox @ Jul 4 2005, 11:25 PM)

people run their Bosch Blue coils with mallory CDI's all the time. why cant i run a hotter coil with the CDI? without buying the CDI 'pulse transformer' which they still call a coil...??

a Pertronix flame thrower is not a Bosch Blue...

you asked:

QUOTE

what would make a coil company say its not for use with a capacitive discharge ignition?

and i thought i answered that. no? i'll try again. PROBABLY they're concerned about insulation breakdown in the primary. Kettering ignitions feed the primary 12V; CDI's feed the primary HUNDREDS of volts.

look at it this way: "what would make a speaker manufacturer say it's not for use in a PA system?" could be because a small speaker designed for good sound in a small room can't handle hundreds of watts of power -- even if they're both 8 Ohm speakers.

yes - some people run some CDI systems through a Bosch Blue. that's probably more a testiment to the Blue coil, and it may be why the Blue coil is only an OK coil - it seems to have way more insulation than it needs...

you *can* run a hotter coil with CDI. which is a rather different question than the one you originally asked, which was why the Pertronix one isn't recommended. probably it's as simple as they're tired of fielding calls from people when their mega-Joule MSD's blew them up because they were never designed to dissipate that much power. go ahead and try it. carry a spare...

also - you're measuring static DC resistance, but what you need to measure (because it is what the coil sees, and the CDI uses) is impedance. no easy way to measure impedance with consumer-level instruments.

i agree the CDI people still call their pulse transformers coils, which is kind of a pity, but the nomenclature has stuck and isn't likely to change any time soon. and yes, if you open one up, you will still see coils of wire inside - like most transformers...

if you want something that'll work with a CDI but still looks like a conventional coil, get the MSD Hi-Vibration coil - it's the only one of theirs that isn't picky about mounting position. or get a Crane LX91 or - like i run with my Crane HI-6 - an LX-92.

don't know why i didn't see the notification of your response earlier, or i'd have replied earlier.