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Coil compatibility
- Thread starter halifaxhops
- Start date
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The spark plugs will only 'take' the voltage they need to ionise the gap. What secondary voltage the coil is able to produce & what it DOES produce to ionise the gap.....are two different things. High end CD systems might dump 600v into the coil primary winding. If the coil's turns ratio is 100:1, then 60,000v can be produced in the secondary...but only 30,000v used.
Inductive ign such as points, HEI etc produce dump less voltage into the pri winding 250-400v so the secondary output voltage is correspondingly less.
Inductive ign such as points, HEI etc produce dump less voltage into the pri winding 250-400v so the secondary output voltage is correspondingly less.
I know there are certain ignition boxes that use only one coil. If you use a different coil they won’t run. Also, the coil can affect how the ignition carries spark energy in higher rpm. I haven’t done a ton of testing with coils and a scope, but I need to.
Dave999
Well-Known Member
the current the coil primary can flow to work effectively
and the current the ignition module or points can supply needs to be well matched
for example an HEI module and a bosch blue coil
module expects 0.6 ohm primary
bosch blue coils come in 3 ohm and 1.8 ohm primary coils for 12 volt 4 cylinder applications
the car will start and run but you will not have much to shout about if its a v8 and you want to go 4000+ rpm
gets complicated with mopar boxes somewhat because the coil and the ballast need to be a matched pair and they need to match the ignition box
easier with points but the wrong ballast in both situations can lead to issues
too little in combination results in hot coil and reduced ignition module life, due to too much current.
Too much resistance in combination and you risk a situation similar to the hei with high resistance 4 cylinder coil.
and the current the ignition module or points can supply needs to be well matched
for example an HEI module and a bosch blue coil
module expects 0.6 ohm primary
bosch blue coils come in 3 ohm and 1.8 ohm primary coils for 12 volt 4 cylinder applications
the car will start and run but you will not have much to shout about if its a v8 and you want to go 4000+ rpm
gets complicated with mopar boxes somewhat because the coil and the ballast need to be a matched pair and they need to match the ignition box
easier with points but the wrong ballast in both situations can lead to issues
too little in combination results in hot coil and reduced ignition module life, due to too much current.
Too much resistance in combination and you risk a situation similar to the hei with high resistance 4 cylinder coil.
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