Ballast resisters

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fuzzman

fuzzman

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I have a question about ballast resisters i converted my 69 318 barracuda from points to electronic ignition. I'm using the orange box and also have a chrome box available. I checked the ohms on the old ballast which measured .8 ohms but i also have a ballast that came with the kit that reads 1.2 ohms which one should i use for the electronic set up? These readings are checked with nothing hooked to the resister.
Thanks
In advance
Pat Faley
67 NB barracuda
69 barracuda convertible
 
The ballast is relative to the coil, the orange box needs a full 12v power source, I usually tap off the 12v side of the ballast.


Alan
 
fuzzman said:
I have a question about ballast resisters i converted my 69 318 barracuda from points to electronic ignition. I'm using the orange box and also have a chrome box available. I checked the ohms on the old ballast which measured .8 ohms but i also have a ballast that came with the kit that reads 1.2 ohms which one should i use for the electronic set up? These readings are checked with nothing hooked to the resister.
Thanks
In advance
Pat Faley
67 NB barracuda
69 barracuda convertible
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The other issue is I noticed with the 1.2 ballast hooked up it gets pretty warm to the point at one point it melted the end of one of the plugs and the back of the ballast is all cracked from it getting so hot I guess. What would cause that?
Pat
 
The 1.2 is more inline with what the electronic is supposed to be used with. I have 3 converted to electronic, all run a resistor between 1.2 and 1.4 with no issues. heat is a by product of its function. I've never seen one get hot and melt the plug.
 
340doc said:
The 1.2 is more inline with what the electronic is supposed to be used with. I have 3 converted to electronic, all run a resistor between 1.2 and 1.4 with no issues. heat is a by product of its function. I've never seen one get hot and melt the plug.
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Anybody got any part numbers on which one to order. I just bought one from rock auto and it is the one that measures .8 ohms it must be for a points set up.
 
Napa Echlin ICR11 (1.35 ohms), Napa Echlin ICR23 (1.2), Napa Echlin ICR34 (1.4), Standard RU-4 (1.35), Standard RU-23 (1.2) and Standard RU-37 (1.4). I copied this off this site a while back, good to have.
 
Thanks, I have been using RU11 and I believe its specs at 1.8 which could be too high?
340doc said:
Napa Echlin ICR11 (1.35 ohms), Napa Echlin ICR23 (1.2), Napa Echlin ICR34 (1.4), Standard RU-4 (1.35), Standard RU-23 (1.2) and Standard RU-37 (1.4). I copied this off this site a while back, good to have.
Click to expand...
 
If you have plugs melting that usually means you have a bad connection that is heating up. Dirty connections have more resistance which means they use power which creates heat. Clean the spade lugs both male and female. You can crimp the female side (the one on the wire) with a pair of pliers so it grips better. The tighter the connection, the better it works.

The 0.8 one will still work temporarily, but you should change it out for the right one as stated earlier.
 
4spdragtop said:
Thanks, I have been using RU11 and I believe its specs at 1.8 which could be too high?
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It depends on the coil and to a lesser degree the amplifier.
Original systems in '73 used 0.5 Ohm to the coil. see 1973 Chrysler Electronic Ignition Diagnosis and Repair, the Master Technician Service Conference (Session 312)
Direct Connection gave 0.5 Ohms as acceptable for coil with all Chrysler units with some exceptions noted.
Those exceptions include the Accel Super Coil (.8 Ohms), coil 5206436 (.7 Ohms) and for racing with certain ECU's, coil P2444641 with .25 Ohms resistor.
fig. 19-3 &19-6 p. 367-8 Mopar Engine Book p4349340
 
Here is information that I found that talks about MP ECU's and MSDs.

This is true with a CD ignition like MSD, Mallory And Crane sell or with any ECU that is internally regulated(like GM HEI or Pertronics). According to MSD(this is not me making this stuff up) the Mopar boxes are not internally regulated and need to have a total resistance (coil primary + ballast) of at least 1.5 ohms. The Blaster2 coil has .7 ohms of primary resistance and comes with a .8 ohm resister for a total of 1.5 ohms. MP's literature on ballast resistors is confusing at best and many catalogs and advertisements incorrectly state that an Orange box and Blaster2 coil can use a .25 resistor. Maybe this is one reason the Orange box has such a bad reputation.

The .25 resister is for racing with a chrome box and a 100 wind coil equivalent to the blaster2. Use under 3000rpm should be limited to less than 30 minutes to avoid overheating the ecu. With no resister it would overheat even faster. Just like the orange box, for street use a .8ohm or more resister is necessary.
 
From MP FWIW...……..

IMGP4783.gif
 
Daves69 said:
From MP FWIW...…….
Click to expand...
Which edition (or cover)?
Looks like its probably earlier than the one I cited. Sorry to see it also has the same terrible copy editting. :(

bbeep71 said:
Here is information that I found that talks about MP ECU's and MSDs.

This is true with a CD ignition like MSD, Mallory And Crane sell or with any ECU that is internally regulated(like GM HEI or Pertronics). According to MSD(this is not me making this stuff up) the Mopar boxes are not internally regulated and need to have a total resistance (coil primary + ballast) of at least 1.5 ohms. The Blaster2 coil has .7 ohms of primary resistance and comes with a .8 ohm resister for a total of 1.5 ohms. MP's literature on ballast resistors is confusing at best and many catalogs and advertisements incorrectly state that an Orange box and Blaster2 coil can use a .25 resistor. Maybe this is one reason the Orange box has such a bad reputation.

The .25 resister is for racing with a chrome box and a 100 wind coil equivalent to the blaster2. Use under 3000rpm should be limited to less than 30 minutes to avoid overheating the ecu. With no resister it would overheat even faster. Just like the orange box, for street use a .8ohm or more resister is necessary.
Click to expand...

That all sounds familiar, and always seemed about right. However, this morning it seemed worth trying to verify the key assertion that 1.5 Ohms is needed.
1976 FSM under electrics shows two coils; one with with primary resistance of 1.6 to 1.79 ohms, the other 1.41 to 1.62 ohms (at 70-80*F).
Same service manual specs the ballast resistor coil side to be .5 to .6 ohms.
Added together equals 1.91 ohms minimum and 2.39 ohms maximum.
Well, that's over 1.5 ohms, and 'they' did say minimum. But I suspect the turns ratio also plays a role. ??? need to brush up on inductance and its effect on current if any, impedance anyone?


"ECU that is internally regulated"
The ballast resistor we're discussing is not used for ECU regulation, its for controlling current through the coil. However, HEI modules regulate coil current and that's probably what the author meant. Factory ECU's connected to a dual ballast resistor, did use the second resistor to reduce their internal operating voltage.
 
Within reason, the value of the ballast resistor probably only affects coil life. If a coil specifies a certain value, that is the one you should use. The purpose of the ballast resistor is to limit the charging current into the coil. The coils are designed with this resistor in mind. the operating voltage on the coil is designed to be less than the full battery voltage when a resistor is used. As with many things, it will work ok over a range of values.

If you have a lower value ballast resistor, there will be more current in the coil. More current can give a hotter spark, but it also translates into more energy consumed by the coil when it is not firing. More energy makes more heat, which shortens coil life.

More current in the coil does not necessarily linearly increase spark output. The output voltage at the coil is largely determined by how fast the ECU breaks the primary circuit (like points breaking the current flow) and the inductance of the secondary circuit ( coil wires, return through the engine block. Higher quality ECUs switch faster and make hotter sparks. The inductance is almost completely dominated by the loop area enclosed by the secondary circuit. This is the path from the coil through the wires, plugs, and return back to tha coil case.

You can think of loop area like a circle. If the wires in the circuit are far apart, there is a lot of area inside the circle. If the wires are close together, it is like squashing the circle flat, not much area inside the circle now. The smaller the loop area, the higher the voltage.

Low inductance is why coils mounted directly on spark plugs are much smaller and work as well or better. There is almost no loop area, so you can get a hotter spark with a lot less primary energy. Remember, peak spark voltage is a strong function of the loop area of the circuit.

If you have your coil mounted off the engine, you should probably have a big honking (technical term) ground wire from the coil to the block, not only to carry the primary current, but also make a short path back to the coil for the spark plug current.

With all that said, the value of the ballast resistor was specified by the coil designer to provide the maximum amount of spark, with a minimum amount of energy wasted to just heat up the coil.

Hope this makes sense.
 
Ballast resistor limits the maximum coil current. It can be calculated using Ohms law. Current = 12V divided by sum of ballast resistor and ignition coil primary resistance. An example : Stock coils typically 1.5 Ohms, ballast 1.5 Ohms. Current max of 4A = 12/3.

Yes energy is not linear with current, it goes up with the square of the current. Double the current, increases energy 4x.

A spark is initiated by high voltage, it ionizes the gap resulting in low impedance, the energy is then transfered via coil transformer. The leakage inductance of coil can limit energy transfer, can coils with axial core have higher leakage inductance than modern e-core designs.

The peak plug voltage is limited by the primary peak voltage times coil ratio, or plug excitation voltage whichever is lowest.

While speed if device that switches coil current increases primary voltage, modern IGBT transistors have built-in voltage clamps for over voltage protection, typically around 400V. With typical 100 turn coil ratio, peak voltage 40kV.
 
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Ignition coils operate in the fly back mode so the secondary voltage is not directly related to the turns ratio. The turns ratio of a typical ignition coil is only about 100:1, not enough to produce 30-50 kv from 12 volts.
 
Are you sure? My many years of experience developing ignitions must be wrong, my cars are all going to stop running.

12V? The negative coil terminal peaks at about 400V, the high secondary would be open circuit, plugs on a mild engine strike at about 4kV. A ballpark arc voltage is 20kV per cm. Most ignitions can jump an inch, about 2.5 cm, that is about 40kV +.
 
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