What is the coil voltage on a Mopar. I have heard it is 7VDC because of the ballast resister as opposed to GM HEI 12VDC or is that only at start-up?
Thanks FABO
Thanks FABO
Coil Voltage
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or maybe he's just asking about the concept.
HEI includes a current limiter.
The other systems of the time, and GM's previous (points) system control the current by reducing the voltage. The more curent through the resistance, the more voltage drops. Chrysler's resistance is mounted such that at driving high speeds it cools more and slightly reduces resistance. That's concept anyway.
Chrysler goes over that here
Ignition System Analysis (Session 259) from the Master Technician's Service Conference
HEI includes a current limiter.
The other systems of the time, and GM's previous (points) system control the current by reducing the voltage. The more curent through the resistance, the more voltage drops. Chrysler's resistance is mounted such that at driving high speeds it cools more and slightly reduces resistance. That's concept anyway.
Chrysler goes over that here
Ignition System Analysis (Session 259) from the Master Technician's Service Conference
Professor Fate
Push the button, Max...
The lower voltage is in "run". Full system voltage in "start". On a stock Mopar system, anyways.
67Dart273
Well-Known Member
The normally brown bypass circuit, IGN2, supplies full battery voltage to the coil for start. The "run" line through the ballast actually goes dead during start. During start you should see whatever the battery is, during cranking, and you want at least 10-10.5V or more
"Running" depends on coil, RPM, charging voltage, a few things. Coil can be all over the map up to around 10-11V
With engine stopped, key "in run" coil might see 6-8V or so
The reason I am asking is that I saw an article on how how much better the HEI system is and that it delivers full voltage to the coil at run. No ballast. This article was showing Mopar and Ford guys how to convert to HEI using their stock distributors as the signal. Claiming to provide better performance. I have a friend who actually did this and hid it all inside an orange box. Wondering if theres any performance gain for the trouble.
Spark It Up: How to Convert a Ford or Mopar Distributor to GM HEI
Spark It Up: How to Convert a Ford or Mopar Distributor to GM HEI
Wow that is really cool and explains a lot. Thanks
I am running a Mallory All-In-One marine disty the correct ballast and a MSD coil. It works fine and has a lot of advance curve options. After reading the article I was curious if there is a hotter spark with an HEI.
Maybe.
We can break up the question into two parts:
The voltage it takes to jump the spark plug's gap depends on the conditions in the chamber, and in particular the conditions at the tip of the spark plug.
density of the mixture, the portion of the fuel that has vaporized -> which depends on the how well its been mixed into the air, along with termperature and pressure in the chamber, and the fuel's distilation curve. I'm sure there's more but you get the idea.
Bottom line is some conditions will require a higher voltage to jump the gap and start the kernal of flame.
Then there is the length of time the current keeps flowing; and how much current flows during that time.
If a fuel and conditions are such that a higher current actually helps the kernal grow, then can sometimes do that better than other systems.
There's guys who can explain this better than me, but thats why its not a cut and dry answer.
Here's what the voltage looks like at the spark plugs.
Notice the voltage to jump the gap is higher than the voltage needed to keep the spark burning.
Then when the electric sparking is finished, there's usually still electical energy left in the system. That's the oscillations.
There's a more technically accurate explanation for the oscillations that others can explain better but to me it represents left over energy.
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67Dart273
Well-Known Member
^^Actually the oscillations "are there" during the firing time as well. If you pull a coil wire "open" you get a very very high voltage spike and very high oscillations during "what would be" the firing time, and then finally petering out. this is known as "ringing" (like a bell). It is cause by the exchange of energy between the capacitor (condenser) and the inductance of the coil. They form a resonant circuit, the coil crashing it's inductance which charges the cap, then the cap discharges back into the coil primary, back and forth
"The usual company line" about condensers/ capacitors in the old points days was that they "keep the points from burning." This is true, but the fact is, that they increase spark energy out of the coil. Without a cap, old school ignition systems will normally not start or run.
"The usual company line" about condensers/ capacitors in the old points days was that they "keep the points from burning." This is true, but the fact is, that they increase spark energy out of the coil. Without a cap, old school ignition systems will normally not start or run.
67Dart273
Well-Known Member
This within limits of engineering "back then" is a misconception. HEI performance is not because of eliminating the ballast per se. You could come up with a coil that would operate directly on 12V that would give good spark output, and of course now, they exist
But "back in the day" some performance coils such as the great big Mallory rectangular coil and even some of the Accel coils USED A SECOND BALLAST in series with the OEM. So they actually used MORE ballast resistance than OEM but got hotter spark out of the coils
Wow so much info. I have been a Mopar die hard for 47 years and I just took the ignition system for granted. Thank you all for the great info. Maybe I should leave well enough alone and start looking at plug coloration for a better picture. My goal is to make sure the setup I have is OK, especially since I am outside the box with a marine disty. Maybe post some pics of spark plugs?
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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in about 2002 I bought a big yellow Accell Super Coil and it's matching ballast. Those two are still on my car, and she went 93mph in the Eighth with those. I am very happy with that purchase.
At first I ran it off the Orange box. But eventually I went to something else. That thing helped my car make fabulous fuel-mileage as well.
At first I ran it off the Orange box. But eventually I went to something else. That thing helped my car make fabulous fuel-mileage as well.
Great information. Thanks
I would expect the GM HEI to provide a hotter spark than the Chrys ign because it uses a more efficient E-core coil. Also GM specified 0.060" plug gaps, 0.080" for some engines, an indication of the available spark energy. The closed magnetic path of the E core design transfers more of the primary energy to the secondary winding, compared to the canister coil. Also, from what I have seen, E core coils have a lower turns ratio than canister coils. The MSD 8225 stock HEI replacement coil has a 70:1 TR, & the Blaster 2 canister coil has 100:1. In practical terms, all else being equal, the lower the TR, the more current in the spark. It is the heat in the current that ignites the A/F mixture. Of course, 60,000 volts [ high TR ] sounds much more impressive than 0.3 amps, so guess which one gets advertised & which ones the fools buy...
HEI use a current limiter inside the module to limit current to 5.5 amps. A very cheap & worthwhile upgrade is the MSD #63647 module that switches 7.5 amps, has a built-in rev limiter & makes a killer ign system.
HEI use a current limiter inside the module to limit current to 5.5 amps. A very cheap & worthwhile upgrade is the MSD #63647 module that switches 7.5 amps, has a built-in rev limiter & makes a killer ign system.
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