coil ohms differences

[young nip]

Hi every one, I was talking to a buddy of mine and were talking coils resistance. Im running 3ohm accel on the xs. He said I could use a alower ohm iimpedance like . 7 ohm accel. I was about to agree that less resistance may be better, question is :is less resistance than 1.5 okay on the xs (79) ignition system or is higher resistance okay. Is the #140403 ( I have these). okay to use instead of the #20-309 Recommended by D Kirk. Whats the diff here between these coils.? Now Im really screwed Up.Gotta find out before my warranty (30) days runs out. Appreciate some info Thanks.
Steve

[Hobbit]

coil math

I don't remember what the standard coil resistanse is, but a 3 ohm coil will draw 4 amps (Amps=voltage / ohms) where as a .7 ohm coil would require 17A. That sounds like to much for the control unit unless the original coil has that low of resistance.

[Hobbit]

coiil math

I just checked one of the older post where someone said that their coil primary was 1.5 ohms.

[young nip]

coils

Wow hobbit I didnt know it would draw so much ,that aint good.17A compared to 4.I was doing some further reading on inductivity and found out that the higher resitance wont hurt the ignition unit.I think with the higher ohm rating you would loose some of the high voltage of the coil but its better than putting that load on the ignition circuitry.Iguess if youre running 25 to 30 kvovlts anyway youre still making juice. Its confusing some of it. Electrical is not my strong suit.
Thanks
Steve

[Dragonrider]

Stick with a coil impeadence the same as stock...the ignition unit is designed/matched for that. Upping or lowering the coil impeadence MAY not damage the unit, but it will not help your performance.

Remember that things are happening VERY fast electrically as far as your coil/igntion system goes at RPM...coils and drivers need to be matched for best performance...

Good luck!

[sixtysix]

Read the coil FAQ, Coil FAQ it has a short discussion on ohms in the section I wrote. Want my take? .7 ohms is not enough, you will burn up stuff. 2.5 or 3.0 seems to work OK but it may reduce the spark energy, especially with the ballast resistor in line, later models (81) did not use the ballast resistor and has a 2.5 ohm coil. 1.5 ohm primary is stock for 78-80 models.