I have two cylindrical ignition coils and I am curious what the below resistance tells me.

Coil A: - to + = 1.10ohms
- to center = 5.07 ohms
+ to center = 5.07 ohms

Coil B: - to + = .80 ohms
- to center = 11.83 ohms
+ to center = 11.80 ohms

Same application: what do these numbers tell me if I swap out B and replace it with A?

Note: These are both 12v coils, just different brands.

Thanks

You'd think that the coil with lower primary ohms would pass more current thru the pri windings and give more output as k.i.s.s. the more energy in means more energy out from the secondary. I'm not sure how the secondary winding proportion (windings ratio) comes into play affecting amperage and voltage (I've forgotten basic transformer theory) but some energy is lost in the transformation but I think the same amount of energy less what the transformation wastes has to come out from the secondary just that the winding ratio will determine how much voltage and how much amperage (I think ). Recently (on here) a guy used a coil with less pri ohms & reported it didn't run as good as another coil did that had more (pri) ohms. Not sure what the secondary turns were & therefore the turn ratio

I'm not sure about the ohm measurements, but I do like to match the coil to the rest of the system. Stock ECU and stock (replacement) coil. MSD ignition and MSD coil ect. Its an engineered system and for durability its best to match the parts up me thinks. I'd choose based on that criteria.

Coil "A" is my 12v FBO coil that I have been using this past year. Coil "B" is my new MSD #8222 (High Vibration) coil.
Last Fall I swapped the FBO ECU for the MSD Streetfire unit and I kept the FBO coil and I have been running it all this year. Even though the SF box says that it will run with most 12v coils, I opted to buy the MSD #8222 unit (per MSD tech support & due to me mounting it horizontally.) just so I could have a matched "brand" set.
What surprised me was the resistance readings between the two coils. I could not find any of the specifications on the FBO coil, but it has ran fine all year. This coil will now be my backup unit.

I was just curious if there was anything to learn from the two different coils brands before I swapped them out this weekend.

Thanks for the replies.

Generally the lower resistance will lead to a hotter spark if it is needed. But an ignition system only builds voltage to the point where it flashes over somewhere, we hope across the plug gap.

Aftermarket coils, many times, had a much lower resistance causing higher current flow through the switching transistor of OEM ignition systems, shortening their life. Certain coils could burn out a Mopar ignition box, for example.

Capacitive discharge is something else, though, and there appears to be a need to get the impedence right for them to work best.
Thus matching the coil to the box CAN BE helpful.

R.

Looking at the numbers only... your coil B will outputting more energy to the spark plug.
Reasons are that the lower primary resistance will allow for a bigger current, and the higher resistance in the secondary winding may indicate that you have more turns which translates to higher discharge voltage (it can also be thinner copper wire showing more resistance with less turns, impossible to know without detailed specs).
It's however not a simple subject, there is more to it, here we only scratch the surface.
Coil B will give you significantly more spark energy, assuming that your electronic box can drive the required current...

Quote:

---

I have two cylindrical ignition coils and I am curious what the below resistance tells me.
Coil A: - to + = 1.10ohms
- to center = 5.07 ohms
+ to center = 5.07 ohms
Coil B: - to + = .80 ohms
- to center = 11.83 ohms
+ to center = 11.80 ohms
Same application: what do these numbers tell me if I swap out B and replace it with A?
Note: These are both 12v coils, just different brands.
Thanks

---