What coil is this, and what's best for the Ultima system?

[1340evo]

So with my new Ultima 2000i that I was going to fit this weekend, it says the coil needs to be 2.5 to 3.5 Ohms for the dual fire intallation.
So Ive checked it and its 3.6 Ohms 

I'm not 100% sure whos coil it is.. it looks like a Accel, but I can only see them in yellow and not black... any ideas? (correction.. I have now seen one in black, so guess it is Accel)

So now the question, if I need to buy a new coil, which way to go... single fire or dual fire?

Reading a few posts for a standard ish engine, dual fire appears to be fine... if so, can anyone recommend a coil to use with this system?
Same question if single fire is the way to go

[kd]

First check your meter and make sure it's been zero'd across the leads before you do the test.

[JW113]

Think big picture here. They're saying the iggy unit needs a solid state type ignition coil, not a points style coil.

Points = 5ohms or so
Solid State = 3ohms or so

Your coil will be fine.

-JW

[1340evo]

I think your rights, its less Ohms that reck electronic ignitions, not a fraction more.

Contact the probes together and you get zero, but I'm taking the coil into work tomorrow to try it on our calibrated meters there.
If it is the Accel unit then it should be 3 Ohms? unless with age they build up more resistance??

[JW113]

I'm not quite sure what you're saying there, but...

Points need 5 ohm coils to limit how much current in amps goes through them. Too low coil resistance will eventually burn the contact points.

Solid state electronic ignitions use a lower ohm coil with higher turns ratio between primary and secondary to get a higher output voltage. Using a points coil on solid state ignition will probably "work", but provide a weaker spark. For bone stock motor, probably not big deal, for high performance high compression motor, probably will not work.

Just my opinion, but throwing too much precision (aka your high performance ohm meter) at crude stuff like this is a waste of time. It's either a points coil, or SS coil. The ohm meter you have has already told you which one it is. You're good to go!

-JW

[1340evo]

yup, just don't want to damage the Ultima unit by giving it too much resistance to work with.

Will still cross check it tomorrow

So where do 4 Ohm coils come in??

[Burnout]

Too little resistance will overload the ignition not too much.

A 5 ohm coil will work but you will not gain any spark output increase.

[JW113]

Exactly!

You won't hurt solid state ignition with more resistance coil.
You WILL hurt ignition points by too little resistance coil.

-JW

[kd]

It's actually DC metal transfer that takes place as the points arc when they open.  A big part of the job of the condenser is to absorb that signal.  If there is no caution on changing the draw on the primary of the solid state circuit it should be OK .10 ohms out of the "suggested range". 

[xlfan]

yup, just don't want to damage the Ultima unit by giving it too much resistance to work with.

Will still cross check it tomorrow

So where do 4 Ohm coils come in??

If memory serves me right, the 4 ohms coil was for the first generation electronic ignition 1978-80.

[1340evo]

Measured at work and its spot on 3 Ohm 

It is an Accel unit.. are these good coils?

[JW113]

As good as any.

-JW

[1340evo]

game on then... lets see what the Ultima's like....