BALLAST RESISTOR........WHAT GIVES?

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CFD244

CFD244

"I LOST MY ID IN A FLOOD"
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Hi Folks

What exactly does the reduced run voltage in the resistor circuit protect? Points (old system), pick-up, control module or coil? I have seen the HEI hack, but in order to eliminate the resistor, do you need to use a different coil (GM or equivalent)? Thanks FABO.
 
HEI. There is one on here that insists on arguing. The HEI modules are capable of sort of "regulating" current on their own. "As an experiment" I ran my HEI conversion with NO heat sink other than being mounted to a flat area of the firewall up near the wiper motor. There "just happened" to be a screw hole right there where somone had anchored something, so I only had to make one more.

I ALSO experimentally used the FACTORY STOCK Mopar coil and it worked just fine. You get FAR better spark out of that combo than a stock Mopar box. I'm SURE that you would get even more with a proper "E" core coil

The ballast: So far as I know ALL US cars of the era used a ballast, and some of the foreign ones. IT JUST MIGHT BE that a big part of the reason was, that by using a resistor (supplying 11-12V when running with the system at 14V) Then they could get a nice hot start with the bypass during start---STILL supplying at least 10.5--11V or more

In the case of Mopars this is NOT just a resistor--it is a BALLAST which means that it attempts--thermally -- to increase current at low voltage and attempts to decrease current with higher voltage. AND the ballast action attempts to sort of stabilize the current over RPM range
 
Conclusion: For best results (spark performance) with HEI, use a compatible E core coil and eliminate the ballast.
 
From the horses mouth. 67 FSM

Screenshot_20221207-200829.png



Another aspect is if the points are closed when the engine is off and the key is in the run position the coil will be continuously energized with voltage and it and the Ballast will have to convert all the wattage to heat.

The ballast heats up like at idle and increases its resistance to help keep the coil from overheating.
 
Yes, the HEI is internally current limited to about 5.5 amps. Problem is that this is more than the Mopar & other ballast resistor coils are designed to work with & run hot without external current limiting with the risk of failing from overheating.
The ign coil current sees the HEI, Pertronix, points etc as just an on/off switch. The coil neither cares, nor knows, what is doing the switching.
If the coil was designed to use a bal res, it should be used with the HEI.
The HEI was designed to use a coil with low primary resistance [ 0.6 ohm ] which provided a high current spark [ the heat in the current is what ignites the mixture, more current more heat ]. A great coil to use with HEI is the MSD 8207 E core coil, no bal res reqd, 300mA.
 
mopar box
Pertonix
points

creatimg a spark from a magnetic feild is all about the speed the magnetic field collapses
the bigger the current the bigger the magnetic field
and the faster you take that current away the faster that field collapses and the bigger the spark.

hence spark power is a function of
how good the coil is at making the magnetic field (no. of turns in primary and secondary, the resistance of both, and the type of material in the core)
how much current flows (linked to resistance of primary and secondary and how many coils of wire make them up)
how fast you can switch that current off and on and how robust your switch is

points good for 3 amps
petronix good for 3 amps
HEI can do 5-7 amps

all but HEI use ballast to limit current. and ballast resistors based on coils of uniform wire do get more resistant the hotter they get.

even 4 cylinder igntions with no ballast resistor make up for the fact its not there by deliberatly adding resistance to the coil primary to make for a simpler install.

none of this resitance helps spark energy at higher RPM, and the faster you go the shorter time there is to have the coil on, dwell reduces,
that in istelf limits current, the faster you go the greater the reduction in spark power.

The main job of the ballast is to limit current at low rpm so you don't cook the coil
ballast and coil run cooler at high rpm becasue they are never dealing with a sustained 3 amps for very long at all.

HEI works differently
it deleiberatly limits current at lower RPM with a circuit that manages dwell time so the coil runs cool. but it still builds up much the same spark power, in the lower RPM range that would see a mopar coil getting really quite hot

at High RPM this circuits influcnce is reduced you don't need to be limiting current when the time you have for coil-on is limited by rpm

hence the output is maintained as much the same as it was at low rpm up to about 6500 rpm. with only limited degredation over the next 1000 or so rpm

hence
standard igntion... spark power limited and reduces as RPM increades
HEI spark power set and the currnet is limited to keep the coil cool at low rpm and the current limiting is removed at high rpm thus maininting more or less the same spark power over the street driven RPM ranges that the 4 6 and 8 cylinder cars tha used these modules operated at....

this all before we get to swicthing speed
you can't switch a coil off and on quicly with points, as soon as they open the coil is not off. there is too much leakage across the gap, a spark at the points takes the edge off a clean switch-off regardless of wheather that spark is due to cutting supply, or back emf once the condencer is full.
this limits spark energy.

the switching speed gives the spark some clout, a spiker spike.

hei uses for want of a better word a high power transistor to switch the coil off
and although these have a measurable time to switch from on to off its a damn sight better than a set or 2 of points

Petronix
quick switching, well quicker than points, but should be used with the ballast and the coil that was there originally. its a hall effect switch so too much current burns out the module in the dizzy.... all the expense for little performance gain.. you just don't have to set the dwell and do any maintance of the points.

nothing wrong with any of them but it depends on your motor

eg mine

6 cylinder 12:1 CR with weber DCOE45s ostensibly a carb per cyilinder port on port induction
standard igntion. flat spot at 2800 rpm as the slow run circuit stopped and i come onto main circuit

HEI ignition No flat spot at 2800 rpm it can light up the inherantly lean mixture at the cross over
meaning i don't have to run rich in idle and progression 850-2800 rpm to get over that hump at 3000 rpm


motor was blowing out the spark with standard mopar electronic and 30 thou points gap
doesn't do that with HEI and 35 thou points gap

track times 14.7s 15.00 s and after change 13.9s

not fast but better than i expected, from an A body with a six, and a driver who is in general terms is better off sitting and watching from the stands

Dave
 
CFD244 said:
Hi Folks

What exactly does the reduced run voltage in the resistor circuit protect? Points (old system), pick-up, control module or coil?
Click to expand...
Points.
Coil.
and on original '5 pin' electronic control unit, the second resistor (5 ohms) is for the ECU.

The pickup sends a small magneticly induced pulse to the ECU. The ECU amplifies it so the solid state electronics do the same job as points, open and close a switch to let power flow through the coil primary windings.

see page 5 "Ignition Systems for 1972" Master Technician Service Conference - Chrysler's Training for Mechanics
 
Great information on this thread. My first car was a 71 demon. The morning after I bought it, I cranked it and it fired and quit, fired and quit, fired and quit. My dad comes running over the hill from the garden and I can almost picture him yelling in that slowed down low yell..."S T O P I T' S Y O U R B A L L A S T R E S I S T O O O R !" I was like, "how in the heck can you troubleshoot a car from the other side of a hill?"

Anyways, I never understood before why it is called a "ballast" and didn't know about the current limining design of it. I mean, yeah I knew resistors change value with temperature, which is why you can't accurately measure a light bulb and predict the current through it at a given voltage but this is really interesting stuff. Thanks everyone.
 
Dave999 said:
mopar box
Pertonix
points

creatimg a spark from a magnetic feild is all about the speed the magnetic field collapses
the bigger the current the bigger the magnetic field
and the faster you take that current away the faster that field collapses and the bigger the spark.

hence spark power is a function of
how good the coil is at making the magnetic field (no. of turns in primary and secondary, the resistance of both, and the type of material in the core)
how much current flows (linked to resistance of primary and secondary and how many coils of wire make them up)
how fast you can switch that current off and on and how robust your switch is

points good for 3 amps
petronix good for 3 amps
HEI can do 5-7 amps

all but HEI use ballast to limit current. and ballast resistors based on coils of uniform wire do get more resistant the hotter they get.

even 4 cylinder igntions with no ballast resistor make up for the fact its not there by deliberatly adding resistance to the coil primary to make for a simpler install.

none of this resitance helps spark energy at higher RPM, and the faster you go the shorter time there is to have the coil on, dwell reduces,
that in istelf limits current, the faster you go the greater the reduction in spark power.

The main job of the ballast is to limit current at low rpm so you don't cook the coil
ballast and coil run cooler at high rpm becasue they are never dealing with a sustained 3 amps for very long at all.

HEI works differently
it deleiberatly limits current at lower RPM with a circuit that manages dwell time so the coil runs cool. but it still builds up much the same spark power, in the lower RPM range that would see a mopar coil getting really quite hot

at High RPM this circuits influcnce is reduced you don't need to be limiting current when the time you have for coil-on is limited by rpm

hence the output is maintained as much the same as it was at low rpm up to about 6500 rpm. with only limited degredation over the next 1000 or so rpm

hence
standard igntion... spark power limited and reduces as RPM increades
HEI spark power set and the currnet is limited to keep the coil cool at low rpm and the current limiting is removed at high rpm thus maininting more or less the same spark power over the street driven RPM ranges that the 4 6 and 8 cylinder cars tha used these modules operated at....

this all before we get to swicthing speed
you can't switch a coil off and on quicly with points, as soon as they open the coil is not off. there is too much leakage across the gap, a spark at the points takes the edge off a clean switch-off regardless of wheather that spark is due to cutting supply, or back emf once the condencer is full.
this limits spark energy.

the switching speed gives the spark some clout, a spiker spike.

hei uses for want of a better word a high power transistor to switch the coil off
and although these have a measurable time to switch from on to off its a damn sight better than a set or 2 of points

Petronix
quick switching, well quicker than points, but should be used with the ballast and the coil that was there originally. its a hall effect switch so too much current burns out the module in the dizzy.... all the expense for little performance gain.. you just don't have to set the dwell and do any maintance of the points.

nothing wrong with any of them but it depends on your motor

eg mine

6 cylinder 12:1 CR with weber DCOE45s ostensibly a carb per cyilinder port on port induction
standard igntion. flat spot at 2800 rpm as the slow run circuit stopped and i come onto main circuit

HEI ignition No flat spot at 2800 rpm it can light up the inherantly lean mixture at the cross over
meaning i don't have to run rich in idle and progression 850-2800 rpm to get over that hump at 3000 rpm


motor was blowing out the spark with standard mopar electronic and 30 thou points gap
doesn't do that with HEI and 35 thou points gap

track times 14.7s 15.00 s and after change 13.9s

not fast but better than i expected, from an A body with a six, and a driver who is in general terms is better off sitting and watching from the stands

Dave
Click to expand...
You are wrong about some of this. The ballast "attempts" to increase current as it cools that is why it's called a ballast

Points don't open "clean?" Ridiculous in the context of the switching speed involved. We are not talking about fractions of a microsecond here. The capacitor is involved maybe that is what you are referring to, but the slight delay caused at points opening is by the capacitor, which starts as an effective "dead short" across the points. The cap coil combination actually INCREASES spark power however. Most breaker point ignitions won't even start if the cap is removed
 
67Dart273 said:
You are wrong about some of this. The ballast "attempts" to increase current as it cools that is why it's called a ballast
Click to expand...

I think this definition is MUCH more accurate than your definition.

Screenshot_20221208-100654.png


And whether it allows more current to flow when cool or less when hot is semantics.
 
Dana67Dart said:
I think this definition is MUCH more accurate than your definition.

View attachment 1716019819

And whether it allows more current to flow when cool or less when hot is semantics.
Click to expand...
???what are you saying??

That IS the definition of a ballast as opposed to a "just plain resistor." A ballast by design uses resistive materials designed to react in such a way.
 
Perhaps a better name for the ballast resistor would be 'balance resistor', as it balances the current available for the coil.
 
No, sorry. "ballast" is the correct name and this comes from the electronics industry. It IS the term for a resistor which changes resistance in order to attempt to regulate current.

In the old days, some circuits used a "ballast tube." These were precision made ballast resistors incased in a vacuum tube envelope and were used in critical circuits to stabilize operation

"Amperite" was one very popular brand, and the name "stuck" as many of us simply called ballast tubes an "Amperite"

Amperite, however, also made time delay relays for warm up timing


Below is an example ballast curve, showing current stability in this case, vs voltage change. They can be engineered for other purposes, depending on the metallurgy of the resistor material

ballast.jpg


amperite.jpg
 
273,
You are missing the point. What I am others are suggesting is that there might be a better term than 'ballast resistor' to describe the function it performs in an ign system. Well aware of it's name in the elcetronics industry.
 
I think ballast resister is the propper term. No need to reinvent the wheel.

Like a previously owned car is still a used car.


There are many other items that are called ballast.

The gravel that holds the railroad track to the bed

A power supply for fluorescent lights

Weight in the bottom of a ship to keep it upright.


All of them have a similar purpose, they steady something, the track, the voltage /current for the light, the balance of the ship.
 
@67Dart273 , thank you for your teaching on this subject. My father was a Master Chief Avionics Technician in the USN and taught electronics both in the Navy and Technical Colleges. He always hoped that I as his youngest son would be interested to learn it from him. At the time it bored me but now I'm fascinated by it. And yes, ballast is the correct term for how the resistor is affecting current flow per the design of this circuit, end of story.
 
i agree, ballast resistor is a ressistor that gets more resistant the hotter it gets. thet are delibertly like this. As apposed to a normal resistor where that behaviour is still presant but is delibertly reduced so its resistance doesn't change when its operating at the temperature range its intended to be used at. a tube radio would never have worked if all resisters in it were balast resistors the circuit specification would be different at every different temperature


Balast used in the igntion circuit so that it gets hot and is higher resistance when you are drving at 20 mph. A time when the points are closed for a long time, it limits the current more when its hot to help moderate coil temperatures, and it gets hot when current flows for long periods. Driving fast cools it down..because the coil is on and off faster and current flows through the balast for shorter and shorter periods of time which is the prefect time to allow a higher current to flow in the coil, you need to build the same magnetic field in a shorter time period, increasing the flow of charge makes sense, and thats what happens when the ballast cools a bit. its resistance to the flow of charge decreases.

the capacitor is there to sink some of the back EMF to help reduce some of the arcing at the points. it stops a big spark at the point between closed and just open. if it did this job perfectly the point contacts would never pip and hole and they'd only need replacing when the fibre foot wore out....

basically when the primary is switched off the magentic field in the coil collapses and the faster it collapses the bigger voltage and current you see at the secondary... nice big spark
but that field is also collapsing around the primary winding as well
voltage in the forward route through the primary built that filed..
so when it collapses you get a voltage the oposite way trying to push back along + wire and suck charge from the - its a back EMF and if its allowed to flow its sucking up energy from the field collapse that would be better used for making a spark on the secondary side

switching speed of points with condencer is fast enough, it works and has done for 100 years. The condencer is there to gve the points a reasonably long life

BUT
that set up is not as close to a stop-dead switch off, of the coil. As a transistor or semi conductor based switch is, becasue the points arc under their 3 amp supply when just apart, and then the condencer needs to fill with charge from the back emf, stopping an evenn bigger arc across the now bigger points gap. if the back emf is flowing in the primary its conflicting and fighting againts the flow in th secondary which is diminsihing the spark power produced by the secondary

so the mopar box providses faster switching and eliminates points but doesn't address the low current design limitations bceaue its still the same old 8volt coil
the petronix provides faster switching but doesn't address the low current design although it does avoid a big external box
the HEI with HEI coil addresses the low current design limitations, the coil can be built with low resistance and different winding ratio to really take advantance of the current
that core made of steel laminates really does hold a bigger feild and crams in more lines of flux in and around the coil

it addresse the failings of the old style igntion set up by being an excessivly large hammer to crack a reletivly small nut

doubling the current doesn't double the magentic field strength it increases exponentially its like 2 and 2/3 as big
the module switches fast and can block up to 400V worth of BACK emf before it sinks it to ground i.e OFF is OFF quicker than with points and it looks much more like totally OFF at the point when the spark starts...points can't do that becasue the condencer is empty it needs to fill up, initially while a few degrees of distributor rotor swing by to allow the points to open wide enough to avoid an arc. while its filling/chargeing up a current flows on the primary side , as it charges the condencer and that has a detrimental effect on spark power.
the spark starts later on, into the period of time it takes the feild to collapse so it wastes the first bit of that collapse.

a car with a busted condencer won't start if the foil in the condencer burns its insulator and shorts out to the inside of the can. i.e it fails with a short circuit rather than an open circuit. its just a Jelly roll /swiss roll of 2 strips of foil rolled and seperated by plastic sheet and shoved in a protective can.
not all condencers are there doing the job of a condencer. A different size of capcitor is sometimes used to suppress radio interance... which would have made a right mess of any AM station you were listening to
no real imapct on FM but might mess with digital i.e music or ecu or computerised race tools/dash....

if the radio supressor fails it can also mean your motor won't start.
a radio interferance supressor is probably more approproate when using HEI.. i have no radio and no supressor...less to go wrong

Dave
 
CFD244 said:
Hi Folks

What exactly does the reduced run voltage in the resistor circuit protect? Points (old system), pick-up, control module or coil? I have seen the HEI hack, but in order to eliminate the resistor, do you need to use a different coil (GM or equivalent)? Thanks FABO.
Click to expand...
Think about vehicle voltage. Remove the primary wire supplying the coil. Connect your DVOM to read battery voltage. Crank the engine over watching what battery voltage is while cranking. You will likely see about 9V. Now hook the primary wire up and start the engine. Check the voltage at the + coil terminal. Should be 8V to 9V give or take.
This was designed in on points ignition, Kettering designed it, so the coil could output the same spark during cranking as when running. Otherwise the cranking spark would be weak making cold starts difficult.
Some manufacturers used a resistor or ballast built into the coil, and three wires to it.
The HEI self regulates.
 
Ballast is what you put in the bottom of a ship to increase stability, discussion over!
 
Have you looked at the backside of a ballast resistor?

Definition: A mixture of coarse and fine aggregate...

Obviously the correct define. It just has a few extra wires attached to it.
 
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