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For best performance use a 0.6 ohm coil with a 0.6 ohm ballast resistor. I posted simulations for the relative performance of that setup compared with a 1.5ohm and a 3 ohm coil. The 0.6 makes much more spark energy above 3000 rpm due to the lower inductance of the 0.6 ohm coil. MSD supply a suitable ballast resistor with a new Blaster 2 coil.
123 ignition manual specifies not to use a coil with lower than 1.0 ohm. Is that the reason why we should add 0.6 ohm ballast to 0.6 ohm Blaster2 coil? Can we use this coil on 123 without the MSD Ignition box?
 

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123 ignition manual specifies not to use a coil with lower than 1.0 ohm. Is that the reason why we should add 0.6 ohm ballast to 0.6 ohm Blaster2 coil?
Yes.
The 123 limits current to 6 amps as well as specifying at least 1 ohm resistance. At low to medium rpm it is resistance that limits current but at higher rpm inductance is the limiting factor. Without the 123 current limit function a 1 ohm coil would draw 12 amps at low rpm but would drop below 6 amps at a higher rpm. The reason that a 0.6 ohm coil will give superior current and therefore spark energy is because inductance and resistance pretty much go together in ignition coils.

It is interesting that the GM HEI module used in Marelliplex can handle a lower resistance than 1 ohm but it limits the current to 5 amps.
 

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Discussion Starter #28
Anyone have any recommendations?

As in something with a product page, so I can order the recommended product.

Unfortunately Beru has limited availability here, please correct me if I am wrong.

Thanks all
 

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From Pertronix, the epoxy filled Flame Thrower models are 40611 for 3 Ohm and 40111 for 1.5 Ohm. They recommend the 3 Ohm and it'll work fine on a stock 4 cylinder, but either will function with the 123. If you search by model number you'll find plenty of places to buy them.

Make sure you get an epoxy-filled model as the oil-filled ones are not recommended for sideways mounting like you have.
 

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Discussion Starter #30
From Pertronix, the epoxy filled Flame Thrower models are 40611 for 3 Ohm and 40111 for 1.5 Ohm. They recommend the 3 Ohm and it'll work fine on a stock 4 cylinder, but either will function with the 123. If you search by model number you'll find plenty of places to buy them.

Make sure you get an epoxy-filled model as the oil-filled ones are not recommended for sideways mounting like you have.


Thanks Gubi

Unfortunately a LOT of bad reviews for this coil, but I may have no choice.

 

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123/MSD coil/ballast resistor installation

Here is my installation. Many years of reliable operation, fires plugs gapped at .040", motor makes 190 HP.
 

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Discussion Starter #36
Ed posted several times it's an MSD coil and resistor combo.



You are not reading very carefully, aren't you?


Got lost in the shuffle of responses is all, no need for hostility.

I’m assuming this is the brand and model:




I’m going to roll the dice on the flame thrower 40111 and see how it goes..
 

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My posts 14, 16 & 31 gave details in different forms. I believe that the resistor comes with the coil when you buy a new Blaster 2 from MSD. Google it, search for it on ebay.
 

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But Mad North-Northwest
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To clarify, if you buy the 1.5 Ohm Flame Thrower 40111 that you pictured you do NOT need a ballast resistor. You'd be fine with the 3 Ohm, honestly: with a stock, non-racing engine the 1.5 is just going to pull more current and run hot. But knock yourself out.

For the record, most modern coils have an internal ballast. The reason they used to use an external ballast is so that the ballast could be bypassed during cranking to get a hotter spark, then put it in series so you wouldn't melt the points during running. With modern electronic ignition there's no longer a need to use an external ballast.

The 123 is designed to operate with no ballast and with a coil of 1 Ohm primary or greater.
 

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Discussion Starter #39
To clarify, if you buy the 1.5 Ohm Flame Thrower 40111 that you pictured you do NOT need a ballast resistor. You'd be fine with the 3 Ohm, honestly: with a stock, non-racing engine the 1.5 is just going to pull more current and run hot. But knock yourself out.

For the record, most modern coils have an internal ballast. The reason they used to use an external ballast is so that the ballast could be bypassed during cranking to get a hotter spark, then put it in series so you wouldn't melt the points during running. With modern electronic ignition there's no longer a need to use an external ballast.

The 123 is designed to operate with no ballast and with a coil of 1 Ohm primary or greater.


Thanks all!

Yah I called Petronix and they said definitely don’t use a ballast.


So bottom line it’ll be:

123 ignition (preprogrammed curves version)

Petronix flamethrower 40111 (1.5 ohms, epoxy filled)

Unknown brand red plug wires (“Alfa Romeo 4 cylinder”)

And I think champion spark plugs happen to be sitting in the engine (I’ll be checking condition and gap soon)
 

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For the record, most modern coils have an internal ballast
Really? Can you give a reliable source for that?
The fact that for most coils the inductance is approximately proportional to the resistance indicates that they do not have internal ballasts. The Bosch Blue coil which is a relic from slow revving air cooled VW's is the only one that I know of but of course it may have been copied by some of the aftermarket folks. Alfa's never used 3 ohm coils, at least from 1966 on and they were less than 1 ohm from around 1982. Why settle for a weaker spark than Alfa provided when you can have a much stronger one.

the 1.5 is just going to pull more current and run hot.
Completely wrong. The 123 controls the current both by limiting the maximum value and by varying the dwell angle as rpm changes. A 1.5 ohm coil comes closer to letting the 123 make the best sparks compared with a 3 ohm coil. It is at low rpm that coils tend to overheat and the 123 prevents that by shortening the dwell angle.
 
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