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Getting Fired Up - How Ignition Coils Work

Interested in picking up a new coil for your 'Vette? There are a few things you should know about how a coil works before you pick the right one for your application.
By Wayne Scraba
Photography by Wayne Scraba
Ignition Coil Tech Mallory
Ignition Coil Tech Promaster
When purchasing a coil, don't... 
   
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Ignition Coil Tech Promaster
When purchasing a coil, don't immediately grab the largest, most powerful unit available. Instead, consult with your ignition parts manufacturer and use the correct coil for the application. As an example, the Mallory PN 29625 coil shown in this photo is designed for use with Mallory HYFIRE series electronic ignition controls, and is ideal for engines that normally operate above 4,000 rpm and up to approximately 10,000 rpm.
Ignition Coil Tech E Model
The newest coils are "E" configurations.... 
   
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Ignition Coil Tech E Model
The newest coils are "E" configurations. If they look more like transformers than old round canister coils, that's because they are. Internally, the design is much more like that of a true transformer. According to Mallory, in this system, less loss occurs during the transfer of electricity due to the closed core of the coil.
Ignition Coil Tech E Model Heat Sink
If you take a close look at... 
   
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Ignition Coil Tech E Model Heat Sink
If you take a close look at this Mallory E coil, you'll see the coil body is surrounded by a series of heat sinks. What's up with that? The idea is to remove heat generated by the coil. Today's modern coil technology can create copious amounts of energy, and that means heat. Getting rid of the heat is important to both coil performance and life expectancy.
Coil Comparison

Conventional Coil

Promaster E Coil

Primary Resistance 0.7 ohms 0.5 ohms
Secondary Resistance 8.9K ohms 8.9K ohms
Maximum Voltage 51,000 volts 51,000 volts
Inductance 6.6 mH 3.56 mH
Turns Ratio 99:1 99:1
Peak Current 190 mA 260 mA
Spark Duration 400 uS 250 uS
Note: Spark tests were done per SAE J973 using a HYFIRE part number 685 for both coil assemblies.

Ignition Coil Tech Mounting Brackets
When mounting a coil, give... 
   
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Ignition Coil Tech Mounting Brackets
When mounting a coil, give some real thought on where and how this thing is going to reside. Vibration is an enemy of many coils. The forces can be transmitted from the race car chassis to the coil, which can have a decided effect upon the life of the assembly. Because of this, companies such as Mallory include special mounts with many of their coil assemblies (race coils included).
Ignition Coil Tech Power Posts
It's not uncommon to find... 
   
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Ignition Coil Tech Power Posts
It's not uncommon to find a car where the polarity at the coil is reversed. This simply means the primary wires are not installed correctly (swapped post for post). Yes, the car will run, and in some cases, rather well, but if you're struggling with a combination that seems inconsistent, check the polarity. It could be cause of the grief.
Ignition Coil Tech Clip Connector
On E coils, the primary wires... 
   
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Ignition Coil Tech Clip Connector
On E coils, the primary wires are not traditional "posts." Instead, these coils use a clip-on connector. If you look next to the pair of primary wire clips (on the coil), you'll find a + on one clip and a - on the other.
Mallory Ignition
Cleveland
OH

www.mrgasket.com
MSD Ignition
El Paso
TX
915/857-5200

msdignition.com

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