MSD or JACOBS Ignition
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MSD or JACOBS Ignition
I seeking a little info regarding these two ignition systems. I was able to find some info through Summit Racing catelogue regarding price and some plain information. What's the most common ignition used for rotaries and could the square coils be used instesd of the round tall coils ?
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Originally Posted by GLC13B
I seeking a little info regarding these two ignition systems. I was able to find some info through Summit Racing catelogue regarding price and some plain information. What's the most common ignition used for rotaries and could the square coils be used instesd of the round tall coils ?
• Capacitive discharge ignitions are commonly called CD ignitions.
• You may see a spec called Operating Voltage. It may say something like 7 to 16 volts. That just means it will operate anywhere in that range. The CD box will probably not function with less than the minimum voltage, and it may break if given more than the maximum. The people who really pay attention to this number are drag racers. They like to run their cars on just the battery, no alternator. They start the day with a battery that may show 14+ volts, and if they forget to charge the battery between rounds, the voltage may drop down below 10.
• The RPM Range spec is only important if the number is lower than your car's redline. If it is, find another CD.
• Primary Output Voltage. This number is how much voltage the CD box is will hand over to the coil - provided the coil can handle it. If the CD box is rated at 500 volts, but the coil can only hold 400, then 400 is all the coil will get. Within reason, the larger number is better.
• Maximum Energy Output. People who post their dyno numbers love this number. It says how much power the CD box is capable of. Like the Primary Output Voltage, this number is dependant on the coil. The Maximum Energy Output is rated in millijoules per spark. It is often abbreviated as "mJ". If you have a turbo or a supercharger and you have problems getting spark high in the RPM band, a big number here will get the spark you're looking for. That also applies to people with oil consumption issues who regularly foul plugs. Although rather than a CD box, they may want to consider saving their money for the rebuild that's fast approaching.
• The last spec will be whether it's an Analog or a Digital CD box. The higher-powered CD boxes will almost always be digital. Digital CD boxes run cooler and can generate higher power levels at higher RPMs.
If you decide to purchase a CD Ignition and you have a semi-normal rotary powered car (that is, something that produces less than 14 gazillion horsepower), then you only need a single CD box on the leading ignition. Lastly, when I bought my CD, I didn't choose a Jacobs or an MSD. I bought a Mallory.
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