I'm planning on installing a Pertronix system in my truck. One question that I haven't been able to find an answer to... what ohm resistance ignition coil do I use? I'm going with a Pertronix Flamethrower III, there are a variety of ohms. I had one person tell me 1.5 is correct? Can anyone clarify?

 

Confusion starts because some people want to use only their Flamethrower coil and the contact points and condensor or, they want to use the Ignitor module and keep the stock coil. The instructions are sort of contradictory whether the ballast is bypassed or removed depending on the configuration. Keeps their tech line busy I'll bet. Finally there are differences in the primary resistance needed depending on whether the engine is a 4 or 6 or 8 cylinder, and whether the Ignitor 1, 2 or 3 is installed.

The V8 wants a minimum of 1.5 ohms resistance in the primary when using an Ignitor module. I think the 4 or 6 bangers need a 3.0 ohm coil. The later Ignitor 2 and 3 modules, I think they can/must use coils with less than an ohm resistance. If you read the instructions for both the coil AND the Ignitor it should make sense, or give them a call, I'm a little fuzzy on those. I seem to recall one has to use their low resistance coils with the newer Ignitor modules. They have a pretty good tech line.

With the Ignitor 1 they caution not to exceed 8 amperes total current in the primary circuit, and this is what the ohms resistance figures are really all about, it's not the voltage per se. I run a 1.5 ohm Flamethrower coil full voltage (no ballast) and Ignitor 1 in my slick with no problems for almost 20 years. If you do the math it comes to around 9+ amperes but, a coil is not "on" 100% of the time, and using 1.5 ohms for the divider doesn't take into account the resistance of the rest of the primary circuit - the wiring and connections.

So 14.5/1.5 = 9.66 amps. I think an ignition coil probably runs about a 60% duty cycle. So it ends up around 6 amperes of current in the primary ignition.

 

The Ignitor lll must use there .03 coil and is a nice unit that is a nice upgrade that puts your ign. system up to date.

I was not disappointed in running all 3 of those the were a simple up grades that all fits under the stock dizzy cap.

I'd say it's as good as running the Duraspark ll setup with out all the ugly wiring harness & it's big module box.
Orich

 

I was going to use the Ignitor III paired with the Flamethrower III coil. I hear a bunch of different answers. I'm not sure what is right.

 

Are you sure the Ignitor III needs the .03 coil?

 

Like I said, they have a Tech Line you can call.

They have a website.

Orich isn't going to steer ya wrong. If ya don't believe him or me or Pertronix, I dunno what to tell ya. The Flamethrower III is a 0.32 ohm coil.

The new Flame-Thrower III coil was developed for use with the new Ignitor III electronics.

It is an ultra low resistance (0.32-ohms) 45,000-volt coil. These new canister style coils were engineed to charge to peak current typically 30-70% faster the other coils. This means maximum spark energy is sustained to higher engine RPM.

These coils are compatible with Ignitor III electronics only."

http://www.pertronix.com/prod/ig/fla..._volt_ft3.aspx