How hot is a coil supposed to get?

[67 Coronet Conv]

Been messing around with coils in my car, got a MSD high vibration (can be mounted horizontal) and this thing gets smoking hot after 5 min of idling. Engine starts spurting and then does. The. Takes a quite a few cranks to fire back up. Is this normal? I did jump the ballast resistor.

67 cornet
440/727
Mopar orange box with no name electronic distb
Just required the engine and upgraded the volt reg and alternator too.

 

[Gus chiggins]

Stock coil would have been fine ( i believe ). Those msd blaster coils tend to get really hot,

 

[Geoff 2]

What did the instructions with the coil say about using or removing the ballast res???

All the Ch ECUs listed in the tech bulletins require a ballast res. If I had to guess: you should be using a bal res [ of the correct resistance in ohms ].

If I had a 2nd guess: because the Ch ECU does not have variable dwell, the coil is 'on' for a long dwell period at idle. This coupled with no bal res, means the coil has a lot of current flow through it & is getting hot....

If I had a 3rd guess: the shut down is the ECU overheating from excessive current flow.

 

[67 Coronet Conv]

What did the instructions with the coil say about using or removing the ballast res???

All the Ch ECUs listed in the tech bulletins require a ballast res. If I had to guess: you should be using a bal res [ of the correct resistance in ohms ].

If I had a 2nd guess: because the Ch ECU does not have variable dwell, the coil is 'on' for a long dwell period at idle. This coupled with no bal res, means the coil has a lot of current flow through it & is getting hot....

If I had a 3rd guess: the shut down is the ECU overheating from excessive current flow.

What is ch?

Is the ohms rating dependent on the ECU or the coil?

Msd instructions say to bypass resistor if running MSD box and use BR if running points distb. No guidelines for this set up

 

[Geoff 2]

Ch: Chrysler.
Ohms rating of the coil or bal res?
The coil & bal res are connected in series, eg 1 ohm coil + 0.5 ohm bal = 1.5 ohm 'package' that the ECU sees. Less res, more current but the ECU will have some sort of limit to the amount of current [ amps ] that it can flow. This is why the coil res is important.
Go the MSD website & check the instructions for use with that coil.

 

[67 Coronet Conv]

Ch: Chrysler.
Ohms rating of the coil or bal res?
The coil & bal res are connected in series, eg 1 ohm coil + 0.5 ohm bal = 1.5 ohm 'package' that the ECU sees. Less res, more current but the ECU will have some sort of limit to the amount of current [ amps ] that it can flow. This is why the coil res is important.
Go the MSD website & check the instructions for use with that coil.

So coil and BR need to add up and match the ohms of the ecu?

 

[Geoff 2]

Sort of......
You need to check the instructions for THAT coil.
If you were using that coil with a MSD 6 'box', the MSD 6 is CD [ capacitor discharge ign ] & works without a bal res. But the Ch ECU is inductive ign, different principles involved & each system has limitations, advantages, disadvantages. Signing off now.

 

[RemCharger]

Just use the ballast .
I've run that combination for years.
No ballast=burnt out box . Try a 1.2 ohm.

 

[Bee1971]

That coil will look like this after 15 minutes on the highway

At least I made it to an exit ramp

And then , we’ll in my case , I literally had four police cars , maybe another dozen interested citizens - While I waited for my wife to deliver another coil I had in the garage

 

[Bee1971]

MSD IGNITION COIL - BLASTER SERIES - HIGH VIBRATION - BLACK​

Universal - Add To Any MSD 6-Series Ignition




.7 OHMs Primary Resistance - Designed for the MSD 6 Series CDI Type Ignition Box running no Ballast Resistor

Like mentioned already in this thread

​

Even with a ballast resistor you are gaining zero performance running that type coil with any Factory Chrysler Ignition Module or ECU designed around an Inductive Type Ignition System

Zero

 

[moparedtn]

Silly question here, part 2 if I may:
As the MSD coil requires a ballast, does that mean installing one in a position other than where
the "stock" one is in the wiring beforehand (in addition to)?
If not, do you add the requirement stated by MSD for their coil to what you already have for a
ballast to begin with - or if the one you already are running meets/exceeds their requirement,
are you good to go with what you already have?

 

[RJRENTON]

Been messing around with coils in my car, got a MSD high vibration (can be mounted horizontal) and this thing gets smoking hot after 5 min of idling. Engine starts spurting and then does. The. Takes a quite a few cranks to fire back up. Is this normal? I did jump the ballast resistor.

67 cornet
440/727
Mopar orange box with no name electronic distb
Just required the engine and upgraded the volt reg and alternator too.

View attachment 1336841

IMO.....First mistake jumping out the ballast resistor. Question is WHY? The resistor is to limit the coil's current and the coil's core loss is a direct function of current x coil's primary resistance equals watts lost or heat. The other issue is you're asking the ECU switching transistor to handle more current as well....that's asking for a failure....probably the ECU first. Electrical devices, specifically transformers have internal insulating materials that degrade with heat, that is cumulative....they DO NOT recover from being over heated.....the effect is additive and will eventually lead to a insulation breakdown and transformer failure....and the coil is an AUTO TRANSFORMER (non isolated or nonmagnetically separated design).
The question that should be asked is: Who instructed you to do this "modification" and the reasoning? Higher spark voltage does not create more horsepower. Just talking out loud......some things are best left as is....."if it's not broke, why fix it" philosophy.......
BOB RENTON

 

[67 Coronet Conv]

So here is some info on what I’m running

Mopar ECU P4120505
No name Electronic Distb

And have these 2 coils

MSD High Vibration Coil 0.7ohms
Calls for a 0.8 BR when using points ignition

Petronius Flame Thrower 1.5ohms coil calls for no BR.

With that ECU, what combo of coil and BR should I run?

 

[67 Coronet Conv]

IMO.....First mistake jumping out the ballast resistor. Question is WHY? The resistor is to limit the coil's current and the coil's core loss is a direct function of current x coil's primary resistance equals watts lost or heat. The other issue is you're asking the ECU switching transistor to handle more current as well....that's asking for a failure....probably the ECU first. Electrical devices, specifically transformers have internal insulating materials that degrade with heat, that is cumulative....they DO NOT recover from being over heated.....the effect is additive and will eventually lead to a insulation breakdown and transformer failure....and the coil is an AUTO TRANSFORMER (non isolated or nonmagnetically separated design).
The question that should be asked is: Who instructed you to do this "modification" and the reasoning? Higher spark voltage does not create more horsepower. Just talking out loud......some things are best left as is....."if it's not broke, why fix it" philosophy.......
BOB RENTON

Coil instructions are stating to by pass BR when running a MSD box or run a BR if running points style ignition. Think the ECU substitutes MSD box. We’ll that got pretty hot, now I’m here seeking advice…

 

[Geoff 2]

You need the bal res with the MSD coil.

 

[Geoff 2]

If you go to page 2 of the MSD instruction sheet, it shows the coil wired with a bal res & the coil [ -] going to points or ign amplifier. That would be the ECU. They are very poor /misleading instructions so I can see how people could be confused.

 

[RJRENTON]

Coil instructions are stating to by pass BR when running a MSD box or run a BR if running points style ignition. Think the ECU substitutes MSD box. We’ll that got pretty hot, now I’m here seeking advice…

The MSD box has different internal circuitry, that may be able to carry more current. The Mopar ECU is specific limited to the factory recommended coil and ballast resistor. I ask again: why do you want to change coils. The 0.7 ohm coil will consume more amps because of the lower resistance, Ohm's law prevails. What was wrong with the origional coil set up, b4 you "started messing around with coils"?
There other factors involved such as the coil's primary winding inductive reactance, the coil's primary winding to secondary winding turns ratio in relation to the ECU's ability to charge and discharge the coil to produce the spark. These all factor into the reliability and longevity of the system.
BOB RENTON

 

[Bee1971]

Some testing back in the day - Click

Mopar Performance ignition coil

 

[RJRENTON]

Some testing back in the day - Click

Mopar Performance ignition coil

The link explains nothing.......just a lot of "what if" speculation but no solutions or recommendations as to specifics and the REASONS for the selection. Wouldn't ET slips of the results of testing different coils under the same conditions that show results, be more worthwhile?
BOB RENTON

 

[Bee1971]

Can you read ?

Explains plenty of what if

On the dyno

"It is an E-core design. I did try an MSD E-core with the MP boxes and about 4500 rpm it started popping and missing.
I am not quite done testing coils and boxes,but someday soon I will have to move on to other things."

Same thing I experienced if you read my posts

OTHERS MAY VARY