Mallory tech answer to coil/ballast ?

[Tom's36coupe]

Reply from Rep:

You need around 1.5 ohms on the primary of the coil. This is between the key-on 12 volt source and the negative side of the coil. So either internal in the coil, loom resistor, and/or ballast resistor adding up to 1.5 ohms is required.
Reply from Customer:

Ok, thanks for the help. The new Mallory electronic coil states not to use a resistor so it has 1.5 ohms?
Reply from Rep:

coil #29219 has the resistance value built in, so no external resistor would be required.

Just got this response today from Mallory about the electronic coil and the correct 1.5 ohms. So it looks like for the last 6 years I have not had to use the ballast resistor. The next question is, how will my system run with a full 12volts, better, hotter spark? cleaner plugs, faster starting?

[BUBBAS IGNITION]

Tom ,

Good post.
Lets do the math:
Using a 1.5 ohm coil AND a 1.5 ohm ballast would give a total of 3.0 ohms resistance.
3.0 ohms divided into 12 volts= 4 amps of primary current ( close to maximum using contact points)
OR volts x amps = watts of 4x12= 48 watts of energy to make spark.

Now : 1.5 ohms with no ballast divided into 12 volts= 8 amps or watts = volts x amps of 96 watts of energy.

Now the problem becomes another issue with the 8 amps being very close to what the electronics can take requiring a current limiting circuit ( for protection) in the control. This could be lower than the 8 amps we figured above.
Example , GM HEI limits the current to 5.5 amps etc......

NOW the discussion can begin regarding to how much spark do you actually need ???
And the fact that a coil will only put out what is required, and the fact that flatheads are fairly low compression requiring very little spark to ignite the air fuel ratio.

[Tom's36coupe]

Now its starting to make sense to me, thanks Bubbas! I guess my thinking has been: 3/4 race camshaft with 380 lift and 250 duration, merc crank, high flo valves, twin carbs and full 12v system with 40k coil. I need full voltage to make the party happen, or do I. If my motor was really lacking in the juice department it most likely would not be running so good. After Jim at Bubbas did the re-curve on my distributor, that was WAY off it really was running strong, the best it ever has, with the ballast resistor limiting the volts. Guess I am your good old consumer, always believing that I need the next best thing!

[Rich/Alabama]

Tom/Bubbas,
Don't want to hijack your thread but this is the info I was looking for so if you don't mind I'd like to pursue it a little further. I have a Mallory unilite on my motor also, the only difference being I recently replaced my dual Strombergs with a Holley 390 carb. I have the 29216 coil with ballast on it now and have been running it this way for a long time, no problems, but was thinking I would change to the 29219 coil and eliminate the ballast. Mallory says the 29216 has .700 ohms primary, secondary 8.9K ohms and puts out 51K volts: the 29219 coil has 1.4 ohms primary, 10K secondary and puts out 58K volts. I'm using the Mallory supplied ballast but don't know the specs, have to ASSUME it's ~.7 ohms or they wouldn't have sold it to me (hah!). That means to me either coil will end up with the same resistance, just higher voltage output with the 29219. Doesn't that mean a hotter spark? It seems simpler to just have to 12 volt power straight to the coil without the resistor and let the coil do the work vs. the resistor. My 29216 coil/ballast are 10 years old and I'm thinking I need to replace them anyway when I re-wire the car soon so this is the time to get to the bottom of this. Thanks,

Rich

[Tom's36coupe]

Rich, I am sure our friends at Bubbas will chime in for some help. I would like to get rid of the ballast resistor for two reasons, clean up the engine compartment wiring and possibly better performance. I always understood that because of the way the combustion chamber is on a Flattie the spark has to travel a long way, just makes sense to me that the hotter it is the better? hey what do I know though, I am just a Jeweler! lol......

[54bomb]

Sponsored Links (Register now to hide all advertisements)

From my experience with Mallory its best to run their whole package, The coil and surge protector. I had a stock ignition and just switched the distributor, then had several issues with the coil and the module inside the distributor. I spoke with the mallory rep and got set up with the correct coil , surge protector and cut out the factory resistor wire. After that it ran great. I wish I knew all that up front. Would have saved me breaking down a couple of times.

[Rich/Alabama]

Tom; Thanks for letting me in. I have a new wiring harness to install and figured I would simplify as well as put a new coil on. I was originally going to hook the electric choke up to the + terminal on the coil but after reading the Holley instructions and talking to others, have decided not to. I agree that hotter seems better or at least can't do any harm. Guess I'll wait and see if Bubbas or anyone else can shed some light on this ballast/no ballast, 51Kv/58Kv before spending any more money. BTW, I have been running the surge protector.

Rich

[BUBBAS IGNITION]

Had a chance to use a current probe today with a couple different ignition coils etc .
After having some problems with various coils we now have our coils made by Andover coil in Layafette Indiana ( usa). We use three different coils being a .6 low ohm, a 1.5 ohm and a 4.0 ohm. All are oil filled canister coils.
The scope waveform shown below is from a contact distributor with ignition points and a 1.5 ohm coil with a 1.5-1.9 resistor in the primary much like we would like to see on a point equiped vehicle. Note that the current is turned on a the left of the waveform and turned off ( ignition fired) at the right. Current is built to a designed limit of a little over 3 amps. (good level for contacts)

The second waveform is the same distributor with no resistor in the circuit, note the rise time increases on the left ( some arcing is shown as well) and the current level is almost doubled ( 6.5 amps).
The spark plug with both ignition coils was firing at 8,000 volts.
The excess heat in the no resistor would have burned the contacts as well and over heated the igntion coil with the lowered resistance.

The same would happen to a electronic ignition controller , however the electronic controller would use a current limiting circuit to control this level and keep the module cool as well as the coil.

As someone said above you really need to use the entire system when buying a aftermarket electronic system.

[Rich/Alabama]

Bubbas,
Just for the record: I am running the entire Mallory system on my car; unilite distributor, 29216 coil, Mallory ballast resistor, and power cell (surge protector) as I said in the last post. Not having any problems, just was wondering if there were any pitfalls in changing over from the present system to the Mallory 29219 coil that doesn't require the ballast resistor, all the other stuff would stay the same. The other part of the question is; what is the significance of the difference in coil output voltage? The 29216 is 51K and the 29219 is 58K. To an ignition novice it appears there might be a performance gain there but your charts imply there may not be any advantage. This discussion is good stuff, I really like to get into the details before spending money after wasting hundreds in the past just trying different stuff that didn't always work. Thanks.

[George/Maine]

I think you are better off with the resister. Keeps the current to 3 amps with a 1.5 ohms resister.This is safer.That would drop 4.5 volts across resister,leaving the rest at coil.If you don,t like the resister put it under dash.AS for the extra volts out of coil,i don,t think you will ever notice it.I'm still running points and mine starts and runs good.

[Rich/Alabama]

George,
You're probably right that I wouldn't notice the extra volts. The car starts at the hit of the button and runs fine so I'm not in a hurry to change anything. I have the resistor under the dash already, Tom said he wanted to get rid of his from under the hood just to clean things up.

[BUBBAS IGNITION]

Originally Posted by Rich/Alabama

Bubbas,
Just for the record: I am running the entire Mallory system on my car; unilite distributor, 29216 coil, Mallory ballast resistor, and power cell (surge protector) as I said in the last post. Not having any problems, just was wondering if there were any pitfalls in changing over from the present system to the Mallory 29219 coil that doesn't require the ballast resistor, all the other stuff would stay the same. The other part of the question is; what is the significance of the difference in coil output voltage? The 29216 is 51K and the 29219 is 58K. To an ignition novice it appears there might be a performance gain there but your charts imply there may not be any advantage. This discussion is good stuff, I really like to get into the details before spending money after wasting hundreds in the past just trying different stuff that didn't always work. Thanks.

I agree with George on leaving it the way it was and has been for years.
The gain in coil output would never be needed on a flathead or any other properly tuned up engine for that matter. Marketing at its best......
High current levels = high heat and high heat damages parts.
Q=Ever wonder why Nascar allows two ignition systems per car? A=They have trouble getting one to run 500 miles at high current levels....

There is three types of voltage in any ignition system.

1=Voltage required. This is what the engine needs to ignitite the air fuel mixture . Rich air fuel takes less and lean air fuel takes more . Higher compression takes more amd less compression takes less.
Typical engine needs 5-8,000 volts under normal loaded conditions and snap throttle may need 10-12,000 etc....
Plug will always only take what is needed (minimum).

2=Voltage Available= This is what the ignition coil could do if demanded ( such as a open wire etc) Maximam output of the coils windings and turns ratio-- Could be anywhere from 20,000 to 60,000 (high energy)

3=Voltage reserve= This is whats left over by subtracting required from available. Using 5,000 and have a 60,000 volt coil this reserve would be 55,000 volts.
I call this the public number on late models. The public can drive their car forever without doing anything to it as far as service , by the time we need 60,000 plus voltage the entire ignition is burned up, melted and destroyed !!!!!!

[Tom's36coupe]

Thanks to all for the answers and opinions.Guess I can blame Mallory, lol.. They are the ones that started me thinking, does not need balast reisistor. Just trying to make the old girl run the best she can, since Bubbas has done my re-curve for me this summer I know its working at its best performance. I am going to hide the resistor somewhere and not worry about it.

[BillM]

It's my understanding that ballast resistors have a temperature coefficient. When the resistor heats up the resistance increases, thus reducing the primary current and producing a regulating effect on the coil current. So if I am correct in this, does it also mean that the coils made for use without a ballast are made with primary wire with a similar temperature coefficient?
I have seen coils said to be designed for electronic ignitions, do you know if they are made without temperature sensitive wire? Seems like they would be just plain wire as the electronics is regulating the current.
Sorry to get into the nitty gritty but I get curious about this stuff.

[George/Maine]

I was looking at Mallary coil and says 1.4 ohms primary to maintain if less add resister.Now if that were so 1ohm you would need 12 amps to run. adding a 1.5 ohm resister would be total of 2.4 ohms that would be 4.8 amps.So it best to keep resister.
But when a coil is made and says no resister needed. When adding lose voltage across resister."More resistince less current "

[Ol' Ron]

Great thread, good information. The Flathead will never see more than 8-10K volts at the plug due to its CR. As far as coils are concerned a stock OEM coil/with resistor will furnish more voltage than your engin will ever need. I was wondering if the Mallory uni-lite distributor had a vacuum advance??

[deuce lover]

Ron,No vaccum advance on the unilite.

[pauldeborr]

I have a 1.5 ohm coil as well and had nothing but problems, always stumbling, I added another 1.5 ohm ballast and it has run perfect ever since.

Mallory Dual Point with a 40,000 volt coil and a 12volt generator, don't know if that makes a difference

[denson1932]

Just a few comments....total watts dissapated is divided between ballast resistor, coil, and point resistance....without a ballast resistor on an ignition system that originally had a ballast; the coil now has to dissapate 4X as much energy because it now has twice the current thru it AND twice the voltage across it! Probally its life is ending soon!
Also the current flo is somewhat less that DC resistance calculations because the coil has DC resistance but also has AC impedance which means a coil will oppose any change in current. So a coil opposes the initial current flo which is why we need 'dwell' to get the coil nearly saturated with current and then the coil opposes an end to current flow which is why, when the points open we have a inductive kick to produce spark....

[BUBBAS IGNITION]

Afternoon news flash !!!

Had a customer problem with poor performance under acceleration. Customer sent in coil and distributor.
I wired it up in the distributor machine , hooked it to battery power and ran it for a period of time watching the output with a single test plug. Primary resistance was 1.5 ohms and secondary was 7,000 ohms .
Heres what happened after 30-40 minutes !! Secondary resistance now shows "open" (still had spark but very weak). Brand name is secret to protect the innocent !!!
Chinese parts suck !!!!

To say this one got hot would be a understatement, oil is everywhere !!!!!

[Tom's36coupe]

Bubbas, It was wired up without the resistor? Are all of the Mallory coils made in China, or just the new stuff, mine is about 5 years old. How about the USA made coils you buy. Do you sell those to customers? Looks like after all of this discussion those of us with ballast resistors better not take them out. Thanks!

[BUBBAS IGNITION]

Originally Posted by Tom's36coupe

Bubbas, It was wired up without the resistor? Are all of the Mallory coils made in China, or just the new stuff, mine is about 5 years old. How about the USA made coils you buy. Do you sell those to customers? Looks like after all of this discussion those of us with ballast resistors better not take them out. Thanks!

This one wasnt a mallory but made in china from another supplier.
Yes we do sell our coils , they are $61 . Havent put them on the web site yet, but will get it done soon...
I didnt have a resistor in the circuit ( the customer said thats the way he was running it) i cant believe this coil got so hot in a few minutes!
I wish i had put a amp probe and scope on it , would have looked interesting for sure. I may try that tomorrow after it has cooled down over night..

[Ol' Ron]

I'm glad to see jim is making coils, at least ypu'll know what your getting.

[denson1932]

Q: did you hook it up to 12V or 6V??...and did you use a series ballast resistor?

[BUBBAS IGNITION]

Originally Posted by denson1932

Q: did you hook it up to 12V or 6V??...and did you use a series ballast resistor?

12 volts and no ballast with electronic module......

[Gasoline]

Sponsored Links (Register now to hide all advertisements)

Hello!

I contacted Mallory regarding my Mallory distributor 27 series with dual points. It needs 3 ohms (original resistance wire 1.5, MSD blaster 2 coil 0.7 and ballast resistor 0.8= total 3 ohm) so I seem to have the right parts installed.

However, the ballast resistor increases to 1.5 when hot, so I´m thinking I could skip it and buy a coil with 1.4 primary resistance and combine it with the original wire resistance wich gives me a total of 3 ohms. What do you all say? My car was shaking and died last week and I thought I solved by changing coil and condenser, but then it happened again the day after. I think this was casued by to much resistance caused by the warm summer (no problem touching the coil). I have no reason to suspect vapor lock, but I do think that the new condenser was bad.

[Bluebell]

Originally Posted by Tom's36coupe

Rich, I am sure our friends at Bubbas will chime in for some help. I would like to get rid of the ballast resistor for two reasons, clean up the engine compartment wiring and possibly better performance. I always understood that because of the way the combustion chamber is on a Flattie the spark has to travel a long way, just makes sense to me that the hotter it is the better? hey what do I know though, I am just a Jeweler! lol......

Tom, It has probably already been cleared up a bit for you, by Bubba's last (and excellent ) post. Though to make point of it, the spark just has to fire the plug (jump the gap) the burning characteristics of the flame front, in a flathead combustion chamber, are another subject, after the fact.

Bubba, I assume that each of these Ballast resistors is there for the sole purpose of completing each particular system, so as to have a higher voltage cold start facility. (if not, I probably missed the whole point)

[Gasoline]

Ok, thanks.

What I want to know for sure is if I can I can choose between two different methods to get 3 ohms so that the points will not get damaged. Are you saying that I should stick to alternative 2?

Alt. 1: skip the ballast resistor and instead buy a coil with an internal resistance of 1.4 instead of 0.7. The effect is the same along with the resistance wire, ie. total of 3 ohms. Also, I know what I get because the ballast resistor increases from 0.7 to 1.5 when it gets hot, which I think could be a problem during extreme summer heat.

Alt. 2: keep the 0.7 ignition coil, 0.8 ballast resistor and 1.5 resistance wire that together will result in 3 ohms.

[FlatheadTed]

The resistor as far as I can tell has a multi function purpose ,The word ballast describes it and it is a stabilizing influence .

[BUBBAS IGNITION]

Originally Posted by Gasoline

Ok, thanks.

What I want to know for sure is if I can I can choose between two different methods to get 3 ohms so that the points will not get damaged. Are you saying that I should stick to alternative 2?

Alt. 1: skip the ballast resistor and instead buy a coil with an internal resistance of 1.4 instead of 0.7. The effect is the same along with the resistance wire, ie. total of 3 ohms. Also, I know what I get because the ballast resistor increases from 0.7 to 1.5 when it gets hot, which I think could be a problem during extreme summer heat.

Alt. 2: keep the 0.7 ignition coil, 0.8 ballast resistor and 1.5 resistance wire that together will result in 3 ohms.

Kinda ?
The issue becomes a wattage issue. Using a 1.5 ohm coil and a 1.5 ohm resistor divides the wattage between the two components. This division also divides the heat built up in each.

[George/Maine]

When a coil is said to be 1.5 ohms and a resister is 1.5 ohms that is not true 3 ohms.
If you put a volt meter across resister it should read about 3 volts that's about 2 amps. A coil is not a resister. best have it running pos at coil to grd about 9 volts.
Best get a know good coil not a master blaster forien junk.

[Gasoline]

This is a great forum!

OK, I´m gonna stick to my Mallory distributor, original resistance wire, MSD blaster 2 coil and the ballast resistor. It might have been a bad condenser (out of the box) that killed my car that sunny day. I also noticed that I installed the condenser bracket upside down so it was pressing against the distributor lock and maybe it did not close properly - it´s a vacuum advance.

[Gasoline]

I must admit that when I installed the new msd coil and ballast resistor recently, I connected the wires wrong, ie. resistance wire to the negative side of the coil and the cable from the distributor to the positive side. The car was impossible to start, but the question is whether it could have damaged the ignition coil and ballast resistor? I discovered it after a few tries.

[B_man_Al]

BillM ...

I'm not sure of the tempco for the ballast resistor, but any coil which is wound with copper wire (all of them I believe) has a positive tempco of .293 % per degree C. Check the spec on the coil, the 1.5 ohms is probably at room temp. Pick a number for the internal coil temp after a hot run .... probably around 80C, maybe more. If so 80C-25C= 55C degrees. The increase in coil temp will then be 55 x .293=16% increase.

If the coil is 1.5 ohms at room temp (25C) then it will increase by 16% at 80C or .24 ohms. The new coil resistance will then be 1.74 ohms.

[George/Maine]

The only way to tell coil resistance is adding a resister like 1.5 ohms for 12 volt car.
OHMS law 1.5 ohms at 2amp is 3 volts, leaving the coil resistance of ?
12 volt minus 3 volts is 9 volts
9 volt didved by 2 amps is 4.5 ohms. E= IxR
A coil used on big truck, vws, other use no ext resister.
I would think its more then 4 amps for 12 volts.
resisters stay mostly what they are rated +-
coil amps is important high amps burns points.

[B_man_Al]

Below are some results I measured on my 8BA with a 6V coil, and a nominal 1 ohm ballast resistor. It has been converted to 12V.

I found the best way to estimate the primary current was by adding another small series resistor ( 0.18 ohms) between the coil and ballast resistor. Or measure the current directly.

Here are the measurements, and the resulting calculated currents and resistances:

Meas Battery V : 11.87V (engine not running, points closed)
Meas V current sense resistor: 0 .752V
Meas V coil (cold) : 4.95V
Meas V ballast resistor (cold): 5.90V

Adding all these gives 11.60V vs 11.87V measured across all of them.

Calculated coil / ballast resistor current = V sense/R sense=.752V/.18 ohms= 4.2A

Calc coil resistance = V coil/I coil = 4.95/4.2A= 1.2 ohms
Calc ballast resistance = V bal/I coil = 5.9/4.2A= 1.4 ohms

The ballast resistor is marked as 1 ohm, so it seems a little high.

As it warms up over time, the current drops to 3.5A and calculates out to 2.2 ohms.

Hope this helps
Al

[BillM]

Found a page on the web that gives a good explanation of ballast resistors. It states there that "Due to a high temperature coefficient of the iron-wire resistor, the hot resistance is about three times of the cold resistance."
See: http://what-when-how.com/automobile/...ms-automobile/

Scroll down to: Output Control Ballast Resistor.

It also states: "The resistor can be installed either internally in the coil or externally in the circuit."

[Bassman/NZ]

Wow. Not good at maths. I have a Bosch SU12 coil which is supposed to run without a ballast resistor (ie, it has a built in one). After reading this thread I'm confused as to whether I should run an external ballast resistor or not. Dist is crab type, system is 12v.

[George/Maine]

If a company sells coils and says no resister needed and your car runs go let it go.
coils topic never ends , people put them is backward use 6 volt coil on 12 volts, measure ohms. If you run a 6 volt coil with 12 volts do you run your car on rode?
If you use a 12 volt coil and resister say 1.5 ohms your current is low about 2 amps.
All testing should be running under correct operation.
If have a car worth 5,10,20,ect k use the best coil you can buy.
Bosch SU12 just for kicks put a amp meter in series and see what it reads running.My guess its less then 3 amps.

[Bluebell]

Confused. Me too.
Here are four common system variations, that I understand.

1. A Ford 6 volt coil is actually a 4.5 volt coil that needs the in dash resistor.
2. An aftermarket 6 volt (true 6 volt) needs no resistor. (bypass the ford resistor)
3.A 12 volt coil can run on 12 volts no resister and no ballast.
4.A ballast coil for a 12 volt system is in reality a 9 volt coil that is used in conjunction with the appropriate external ballast.

The resistor in No1. is Fords way of aiding starting from cold because as the resistor heats up the voltage to the coil drops to the 4.5 volts from the 6 volts it gets when the resistor is cold.

The ballast system is another cold start aid for a key start system. When the key is in the cranking position, the ballast is bypassed, feeding the full 12 volts to the coil. when the key is released the feed to the coil is directed through the ballast resistance and so the coil is fed only 9 volts while running.

I understand that the electronic systems need a special coil?

Bubba, can you please answer these for me;
1. Are there coils with built in ballasts, or am I missing something?
2.What are the applications (when are the different ones used) for the three different primary?) resistances that you mentioned?

[B_man_Al]

BillM … thanks for the link to the coil site. Well I guess I got to eat some crow here. Didn't know that coils designed to work without a ballast resistor, have them built in! Makes sense though, to allow the primary current to increase at higher speed where the dwell time is reduced. The reduced dwell time (points closed) allows the ballast resistor to cool, thereby reducing its resistance and allowing an increase in the primary current.
Never too old to learn!

[Tom Walker]

I am struggling with a mis-fire at high revs, under load, when my engine is hot. I am still trying things one at a time to dignose the problem (ie is it fuel vapoisation or sparks).

So I have been reading this thread very carefully, and there is alot of information here, some of it hard to make out though.

My question, something that has occurred to me as I read...if the resistance in a ballast resistor increases with temperature, does the resistance in the primary windings of a coil not also increase with temperature? If so should this not also be factored in?

Cheers, Tom.

[B_man_Al]

Tom .. Yes the coil resistance will go up with temperature as I posted in post #34. But because the ballast resistor is made from a special steel wire, it will increase a lot faster with temperature than the copper wire in the coil.

This will also happen with a coil with a built in ballast resistor. But since the two are internal, there is no way to separate the two for measurement purposes.

As posted by BillM, if the ballast resistor increases 300% ( 3:1) with temp, and the coil primary copper wire, only increases 16% over the same temp range, the dominant change will be due to the ballast resistor, though both contribute to the overall resistance change.

[B_man_Al]

In post 36 I tried to explain what I did to determine the current and voltages associated with my 8BA coil/external ballast resistor combination on a 12V system. Key to the whole thing are two factors.

1-Do the measurements with the engine off, and the points closed. If you measure with the engine running you will get errors due to the voltages not being stable (points opening and closing constantly). If you have a scope, you can get accurate voltage measurements, but not with a multimeter.

2-Add a small series resistor ( Rsense) to allow the accurate calculation of the current, ( I coil = V Rsense/ R Rsenser) or do it directly. I used 0.18 ohms cause thats what I had, but any value that is 10x or more smaller than the coil + ballast will be fine. The lower the better to get better accuracy. This needs to be done, because the added sense resistor is designed to be stable with temp, and not vary all over the place like the ballast or coil resistance.

You can only calculate the current accurately if you know what the resistances are.

If you measure the current directly with a multimeter, then you don't need the sense resistor.

So the steps are:

1-turn off the engine, with the ignition on
2-measure the voltage applied to the ignition cct ... (ballast + coil ...nominal 6 or 12v)
3- measure the coil current , either directly or with a small sense resistor added.
4- Calculate the ballast resistance .... R ballast = V ballast/I coil
5- Calculate coil resistance ... R coil = V coil/I coil.

Check to see if results agree with the coil/ballast specs.

These need to be done quickly as the ballast and coil resistances will be changing quickly as they cool off.

[BUBBAS IGNITION]

I understand that the electronic systems need a special coil?

Bubba, can you please answer these for me;
1. Are there coils with built in ballasts, or am I missing something?
2.What are the applications (when are the different ones used) for the three different primary?) resistances that you mentioned?[/QUOTE]

WOW this thread has went on and on , some facts , some not !

The working resisitance of the coil is designed with the winding and how the windings are installed etc. I know of no coil with a internal "ballast resisitor" The working resistance is a factor of the windings. See picture of exploded coil
windings and a new winding in a delco coil. ( Both Indiana made)

The parts in a ignition system are designed for a specific current flow and voltage drop . Both must be considered in every discussion.
Once the system is designed the current draw is pretty much constant value based on system design and resistance of components.
Lets discuss voltage first. On a common 12 volt system the ballast of loom resistor drops the voltage to 6 volts and then the coil drops the voltage another 6 volts = low voltage at the contacts etc. Actually the battery is 12.2 or 12.4 volts and the extra 2-4 tenths of a volt is dropped by using a special finely stranded primary lead to the points from the coil. In reality there would be only .2 or so volts applied to the contacts in a perfect world.
Now start the engine and the voltage changes to 14.6 volts , the ballast and ignition coil would drop this extra hit of voltage as they heat up due to the voltage increase.
The current is another story. As a contact system may use a 1.5 ohm resistor and a 1.5 ohm ignition coil. The total resistance would be 3 ohms and three ohms with 12 volts would use 4 amps. 3-4 amps is pretty typical current flow for a contact ignition. This amp flow would be constant thru out the entire primary system.

The three coils we see the most ( 12 volt) are :

1-1.5 ohm coil= contact ignition system and some electronic ignitions
2-.5 ohm coil needed for current controlling electronic systems like the GM HEI ignitions etc.
3- 3-4 ohm coil used with no ballast systems as the ignition coil has it built in. Used mainly in fours and sixes as the dwell time is longer on these units and coil saturation is better.
We do not suggest these to be used on a v8 engine with smaller dwell cycles......

We also suggest using a ballast and ignition coil as this divideds the wattage of the units and lowers the heat build up by using two units in lieu of one..

pictures in next post...

[BUBBAS IGNITION]

Sponsored Links (Register now to hide all advertisements)

The real issue!!!

You have got to assume that the factory did its job when they designed and made millions of vehicles and most every ignition system in all brands ran for a very long time before ever needing any service at all .......
The problems only occur after we ( all of us) modify the factory system from it factory shape and design.
I hear the comment every week: " My car is eating coils !!!" thats a easy answer the only way we can eat coils is to have too much heat and the only way we can produce too much heat is by lowering the factory ressitance of the circuit. Usually using the incorrect parts !!!

[George/Maine]

B man Al
I want to know if you drive your car with a stock 8ba 6 volt coil and a 1 OHM resister.
I don, think you will get 100 miles.
Why would you want to do that.
Buy a 12 volt coil and matching resister , low amps about 2 amps.
ever knowtis the size of wire on 6 volt car it larger.12 volt car can use smaller wire because of less current.

[B_man_Al]

Hi George ...

My 8BA is not on the road yet, so its only running in the garage occasionally. This is the one I did the measurements on. However I converted my 4 cyl Model B to 12v the same way in 2007 with no problems. Its been 5 yrs now and about 6000 mi. Almost all the miles are racked up on tours with the model A club, so the runs are usually all day long during the summer and fall.

The ballast resistor comes from MACS, part number A12001 and is recommended for converting 6V coils for 12v operation. I'll go make some measurements in the next day or so.

I'm curious why you think the current should be around 2A. A 1.5 ohm coil and a 1.5 ohm ballast will be around 4A peak when cold and drop to about 2-3A when hot due to the increase in resistance of the coil and ballast with temperature.

If however you take the AVERAGE current it will likely be in the 2A range because the points are open for part of the cycle, and therefore current is not flowing .

[George/Maine]

This is very interesting macs # A12001 what is the value of this resister.
I'm just guessing a 8ba coil needs about 3 amps to work.
When you match a resister with same value coil it works ok.
Buy adjusting resister higher or lower to match coil specs.
I guess that's a way to use and old 6 volt coil.
I did a test on mine just to see what values I would read.
I used a 12 volt coil IC13,(THIS IS SAME SIZE AS 1949 coil)and ICR 13 resister 1.82 ohms. I read about 2 amps +or-
This info is from Echlin parts book but doesn't go back to Model a.
That resister must have a high watt rating at least 20 watts.
I can see now it works for you.
Good Luck
George

[Bassman/NZ]

I'm starting to understand this now. As I see it, the optimum resistance for a 12v coil would give around 3 amps? This is to prevent burning at the points. This would necessitate a resistance of around 4 ohms total. Am I on the right track?

[Bluebell]

Just to add to, and recap Basemans post. We arrive at the the above results using the 1.5 ohm resistor wired in series with the 1.5 ohm (12volt) coil that we should be using with a V8.
So.... when buying the resistor. Are they identified (rated?) at 1.5 ohms at operating temp (as if the engine is running) What do we buy?

[BUBBAS IGNITION]

Originally Posted by Bluebell

Just to add to, and recap Basemans post. We arrive at the the above results using the 1.5 ohm resistor wired in series with the 1.5 ohm (12volt) coil that we should be using with a V8.
So.... when buying the resistor. Are they identified (rated?) at 1.5 ohms at operating temp (as if the engine is running) What do we buy?

Yes they are rated , NAPA has a buyers guide that lists all electrical automotive products , there are many pages of resisitors ( and loom wire resistors) each oem manufacture designs the system for correct current loads etc..

This same guide also has pages of ignition coils etc ..
My experience as a technician working on these cars is that most of the time the problems are created by using the incorrect parts during a repair. Imagine a vehicle with the wrong ignition coil , the wrong resistor and the incorrect condensor all at the same time !!! We see this all the time ..

[Bluebell]

Well Bubba (with me) at age 60 you have enlightened me.

[B_man_Al]

Just to keep a good thread going, and to answer George. My 32 4 cylinder with the MACS A12001 ballast resistor gives a current of 4A when not running and just turned on. (Ballast resistor cold). After a few minutes the resistor gets hot to the touch but the current only drops to 3.9 A. So there may be ballast resistors that have a 3:1 value change, but not this one. Its virtually the same over temp. The voltage drop across it is 6.15v at 3.9A which calculates to 1.58 ohms.

My dwell is set to 38 degrees, which gives a 42% make time for a 4 cylinder. So the average current would be 3.9A x .42 = 1.6A at 12V. Because the voltage increases to around 14v when running, the average coil and ballast current will be 14/12 x 1.6 = 1.9A

Al

[George/Maine]

The resister you are using must be for a model A coil when going to 12 volts.
the 8ba coil maybe the same ohms.
Of the testing we have done your coil must be about 2 ohms,2ampsx 3.9=7.8plus the 6.15 across the resister.=14 volt total.
my testing was 2 amps and value of coil 12 volt is about 5 ohms.
So the tests have shown there is a difference in ohms for 6 and 12 volts coils.
I,m running a 12 volt coil with low amps and has been good so far.
Macs doesn't show that resister any where else but model A section.
I don't think that's the answer for converging a 6 volt car to 12 volts.

[B_man_Al]

Hi George ...

I just went to the MACS website. Typed in 32 ford and the A12001 came up as the resistor to use for a stock model B coil when used for 12v operation.

http://macsautoparts.com/campaign_pr...1932&make=Ford

[George/Maine]

I did see it in model A but didn't look in Model B
I try to get a matched coil and resister.
Seeing this is a Ford site my parts catalog NAPA ECHLIN
Says for 12 volt system point don't seem to care.
I would use IC 10 COIL, and ICR 11 Resister 1.35 OHMS
from 1956 to 1969 later but cat only goes to 69.
All this testing shows there is a difference with 6 and 12 coils.

[Gasoline]

Hello again!

Which is the best ignition coil for a Mallory 27 series (dual points)? I´m already using a MSD Blaster 2 with external ballast resistor, but I´m gonna buy an extra ignition coil/ballast resistor and keep it in the toolbag.

I was tuning the carburetor (during idle) yesterday and I noticed that my MSD Coil was getting quite hot (140 fahrenheit) and so did the condenser. Is that ok? The coil is placed in front of the engine, to the right side of the distributor.

[BUBBAS IGNITION]

Originally Posted by Gasoline

Hello again!

Which is the best ignition coil for a Mallory 27 series (dual points)? I´m already using a MSD Blaster 2 with external ballast resistor, but I´m gonna buy an extra ignition coil/ballast resistor and keep it in the toolbag.

I was tuning the carburetor (during idle) yesterday and I noticed that my MSD Coil was getting quite hot (140 fahrenheit) and so did the condenser. Is that ok? The coil is placed in front of the engine, to the right side of the distributor.

The MSD Blaster series coils ( # 8302,8303 etc) are designed for electronic ignition systems with current control, not for use with a point distributor.
They have a primary resistance of .7 ohms and draw high current. Even when used with a ballast they will draw excessive current causing the contacts to burn up pretty quick.
Thats the reason the coil is hot !! More than likely drawing 8 to 10 amps ...

[Gasoline]

I am at the garage right now. I measured the voltage on the positive on the coil. It is only 6 voltage with ballast and 7 without. This was strange, but perhaps why the car was shaking and finally died the other day. I must have bad wires? Is the coil bad? There is something stealing power? It is also difficult to start. The goal is to have 9 voltage on the positive side on the coil? Thanks for all the help so far.

[BUBBAS IGNITION]

Trying to help ya here ........

Trying to help you here:
from above post

The MSD Blaster series coils ( # 8302,8303 etc) are designed for electronic ignition systems with current control, not for use with a point distributor.
They have a primary resistance of .7 ohms and draw high current. Even when used with a ballast they will draw excessive current causing the contacts to burn up pretty quick.
Thats the reason the coil is hot !! More than likely drawing 8 to 10 amps ...

You need a 1.5 ohm coil ( which you do not have ) and a ballast resistor of approx 1.5 ohms as well. This would drop 6 volts at the resistor and another 6 volts at the coil negative side allowing only a small amount of voltage ( mili volts) to travel thru the contacts.
You dont want 9 volts at the coil ( only when cranking) and it really isnt about voltage anyway, its the high current going thu the low resistance coil causing the coil to heat up.

Your question was why does my coil get hot????
The reason the coil gets so hot its the wrong coil for the application...

[Gasoline]

Thanks! I will remove the MSD coil. It was actually MSD electronic service that told me that if it is 9 volts on the positive side on the coil I´m good, but if it is less , I would remove the resistor.

Here are the results from todays test during idle:
MSD Blaster 2 (0.7 ohms) with resistor= 6 voltage on coil positive.
MSD Blaster 2 without resistor= 7 voltage on coil positive.
Accel 8140 super stock (1.5 ohm) with resistor= 8 voltage on coil positive.
Accel 8140 super stock without resistor= 9 voltage on coil positive.

So you are saying stick with the Accel 1.5 ohms and the resistor 0.8-1.5 ohms?

[BUBBAS IGNITION]

Originally Posted by Gasoline

Thanks! I will remove the MSD coil. It was actually MSD electronic service that told me that if it is 9 volts on the positive side on the coil I´m good, but if it is less , I would remove the resistor.

Here are the results from todays test during idle:
MSD Blaster 2 (0.7 ohms) with resistor= 6 voltage on coil positive.
MSD Blaster 2 without resistor= 7 voltage on coil positive.
Accel 8140 super stock (1.5 ohm) with resistor= 8 voltage on coil positive.
Accel 8140 super stock without resistor= 9 voltage on coil positive.

So you are saying stick with the Accel 1.5 ohms and the resistor 0.8-1.5 ohms?

Yep, but even more important , did it get hot ???
That was the issue right?

[Gasoline]

Thanks, I have to drive more to be certain. It did not get hot yesterday when I was testing with different coil. I wonder: How can a coil with 1.4 resistance result in higher voltage than a coil with 0.7 resistance? Should it not be the opposite?

[B_man_Al]

The voltage across the coil is determined by both the ballast resistor and the coil resistance. If the ballast resistor is the same in both cases, the voltage across the coil will be less for a lower resistance coil. The voltage divides according to the ratio between the two. So if the ballast is 1 ohm for instance, the coil voltage will be V bat x R coil/(R coil + R ballast). WITH THE ENGINE OFF AND THE POINTS CLOSED

So with 1.4 ohms : V coil = 12 x 1.4/(1.4+1)=7v and I coil = 12/2.1= 5.7A
With a .7 ohm coil: V coil = 12 x.7/(.7+1)=4.9v and I coil = 12/1.7= 7.05A

[Gasoline]

Sponsored Links (Register now to hide all advertisements)

Thanks for the clarification.

However, the results that I mentioned before are taken during idle:
Accel 8140 super stock with resistor= 8 voltage on coil positive.
Accel 8140 super stock without resistor= 9 voltage on coil positive.

Done with the key on and engine off:
Accel 8140 super stock with resistor= 4.7 voltage on coil positive.
Accel 8140 super stock without resistor= 5.7 voltage on coil positve.

Is that not to low and should I not skip the ballast resistor after all?

Just so I´m doing it correct: I measure coil positive with all wires connected and multimeter red wire to the positive side and the black wire to the ground on the car?

[B_man_Al]

Gasoline ...A couple questions:

1- Are your key on/ engine off measurements in ohms or volts? It says ohms.

2- What is the measured resistance of the ballast resistor and the coil measured individually?

3- I'm assuming a 12V battery is being used ?

PS I did the math wrong with a 1.4 ohm coil it should be 12v/2.4 ohms = 5A, not 5.7 as I posted previously.

Is the multimeter you are using to measure the voltages a digital one?

If the 8140 without a resistor is connected to 12v, the 5.7 must be 12v or else there is something else in the path to reduce the voltage to 5.7. ( assuming the 5.7 is volts and not ohms)

[Gasoline]

1. My mistake, I just changed it to voltage.

2. I´m not sure what you mean. Ignition coil resistance is 1.4 and ballast resistor is 0.7

3. Yes, and I´m using a digital multimeter.

I probably have a resistance wire/loom resistance that reduce the voltage.

Skip the ballast resistor?

[Ol' Ron]

Kind of a wast of time and money to use a Unilite distributor or any with a vacuum advance, unless it's in a racing application. For street 90% of your driving is at part throttle, so your timing is retarded.

[Gasoline]

I use oldfashioned points. That is why I'm so concerned about the ballast or not. 9 voltage on positive on coil when running and 5.7 with engine off and key on is ok regarding to Mallory, but I trust you guys more. What do you all think?

[George/Maine]

You would better to go to parts store like NAPA, Macs auto has what you want.
this is for a 1957 Ford and others
B6A-12029-B
Do not use this coil on any vehicle equipped with transistorized ignition. 1964-1966 Thunderbirds offered this type of ignition as an option for the 390 & 428 engine. The ignition coil, if used in any type of vehicle with a transistorized ignition system WILL NOT WORK and may result in other electrical problems and may even burn out or damage other parts.

[B_man_Al]

Gasoline … hope you dont glaze over here, it’s a long one!

I think the digital meter is giving you false readings when the car is running. This is because the meter is set to DC (I presume) , but the voltages are not a steady DC as the current is being interrupted by the points. Also you can get some pretty high inductive kicks back from the coil which really confuses a digital meter. That's why I keep telling people to measure with the engine off, and the points closed. Only then will you get accurate DC readings.

I asked about the ballast and coil resistance readings because I'm trying to figure out if your numbers are MEASURED or are they the mfg SPECS.

NO BALLAST RESISTOR CASE, ENGINE OFF:

Let’s assume the coil is 1.4 ohms, and the ballast is 0 ohms (not there) as stated.

From your measurements the coil voltage is 5.7v and the resistance is 1.4 ohms. This makes the steady state DC coil current 4.07 A. (I =5.7/1.4)

If there is no ballast resistor, then the loom resistance must be dropping the rest of the voltage = 12V-5.7V = 6.3V. This makes the “loom” resistance = 6.3V/4.07A= 1.5 Ohms

.7 OHM BALLAST RESISTOR CASE, ENGINE OFF:

Let’s assume the coil is 1.4 ohms, and the ballast is .7 ohms as stated.

From your measurements the coil voltage is now 4.7V and the resistance is 1.4 ohms. This makes the steady state DC coil current 3.36 A. (I =4.7/1.4)

The voltage across the ballast resistor becomes .7ohms x 3.36A = 2.35V

Now the loom resistance must be dropping the rest of the voltage = 12V-4.7V-2.35V = 4.95V . This makes the “loom” resistance = 4.95V /3.36A = 1.5 ohms

In both cases, the “loom” resistance comes out to 1.5 ohms, so that must be the correct value, and all the numbers make sense.

I would suggest that you make an actual measurement of the current with the multimeter to confirm, (with the engine off and the points closed).

If you confirm these numbers, then it is easy to calculate the peak coil current when running as follows:

I coil running = I coil stopped x 14/12 (assuming the generator/alternator is putting out 14v)

Then :

I pk with Ballast resistor =3.36A x 14/12 = 3.92 A
I pk without Ballast resistor =4.07A x 14/12 = 4.75 A

Finally to get the average running current (which determines the heat of the coil), take the peak currents above X dwell angle/45 (assuming a V8 engine)

Assuming the dwell is around 30 degrees, the numbers become:

I avg with Ballast resistor = 3.92 A X 30/45 = 2.61A
I avg without Ballast resistor = 4.75 A X 30/45 =3.16A

These current numbers seem quite reasonable to me, and its not clear if the ballast resistor is required. From the above calculations, the majority of the current limiting is in the “loom resistance” of 1.5 ohms, and not the actual ballast resistance of .7 ohms

Hope this isn’t too complicated, but that’s life!

[George/Maine]

I,m not a engeener ,i use parts from cars of proven desine.
You can use any parts you like,Ford 1957 coil and resister.
In all the cars i have owed i have never had to replace a coil.
I like to know for test facts of using what i run on my car.
The only thing that is known is a rsister of say 1.5 ohms.
Tests should be done when running thats what its all about.
Simple read acorss resiter 1.5x2 amps (i)=3 volt,1.5x 2.5=3.75 volts,1.5x4=6 volts.
The higher the amps the higher the volts.If the amps are to high you loose voltage to coil.
The ohms reading means nothing to me only that you have a open coil.
So my car is about 3 volts running 13.8 volts, coil is about 10 volts.thata about 5 ohms.
I don,t like digital meter,anolog meter is better.
use what works for you ,all the problem are the master blaSter, flame thrower high end parts that do,nt seem to work.Keep it simple
ever knowtis they never sell a complete packagefor electrtinic dist most always buy coil exta.
So watch the amps read across resiter 3 volt, known resister 1.5, 3 divderd 1.5= 2 amps.

[B_man_Al]

George .... your right about 1.5 ohms x 2 amps being 3 V . That's called ohms law. But what you are missing is the fact that when the car is running, the 2A is only flowing while the points are closed. When the points are open, (about 30% of the time) the current is not 2A, its 0A. So the meter (analog or digital) is going to average these two currents and come up with what your measuring ..... 2A. But the real current flowing is nearer 4A if the ballast and coil are both 1.5 ohms. You would see the current going from 4A to 0 A as the points open and close on a running car if it was measured with a scope, but NOT WITH A MULTIMETER. It cannot react fast enough to give an accurate reading. Its kinda like your bank account, one day it has a $100 in it , the next it has $0. Over the two days the average in the account is $50, not $100.

[George/Maine]

B man Al
I did the test again 3 meters 2 ohms scale need batteries.
The resister is about 2 ohms and voltage is 2.6 volts ,
battery is almost 14 volts.
2.6 divided by 2 ohms=about1.3 amps.
This is getting to technical for me.
I guess if you use know correct parts there is no need for meters.
Keep them running.
George

[B_man_Al]

George ..

Here's a test you can do to illustrate what I'm trying to say. Make the measurement you usually do with the car running. Clip the meter across the ballast resistor and measure the voltage. Lets say you measure 3V as before.

Now turn off the ignition, and turn it on again after the engine has stopped. Either the voltage will be 0 volts if the points are open ( no current is flowing) , or the voltage will increase to around 6V if the points are closed. (This assumes the ballast and coil are both around 1.5 ohms).

If you get 0V, hit the ignition momentarily until the points close.

In this case, as you have noted before, the current should be V ballast/R ballast = 6v/1.5 ohms = 4A.

From this you can see that the voltage increases across the ballast resistor when the points are closed, and the engine is off, even though the applied voltage has dropped from around 14v to 12v. The only way this can be true is if the meter is reading a reduced voltage when the engine is running due to the "averaging" going on.

Make sense?
Al

[Gasoline]

What can I say; I am impressed by your knowledge and I have read all posts carefully.

To sum up my problem: car shakes, dies and impossible to start on a sunny day. I change MSD 0.7 coil + 0.7 ballast resistor to a new MSD 0.7 coil and 0.7 ballast resistor, change condenser and the car starts fine again later that day. Then, the same thing occurs the day after after driving for 10 minutes. This happened once for the past seven years and that time it was caused by a bad condenser.

This time a start thinking the coil does not get enough power and the warm summer weather increases the resistance. I measure and notice that I have only have 6 volt so I change to a 1.5 ohms Accel coil and the volt increases to 8 when the engine is running (still using 0.7 ohms ballast resistor). I try without ballast resistor and volt increases to 9 when engine running.

So I am thinking that maybe I should be satisfied with 8 volt using a resistor (only 6 volt with the MSD which obvious was to low for my car). But then I am thinking that I might need 9 volt, by skipping the resistor, so I do not end up with the car shaking/dies again. But 9 volt might be bad for the breaker points - so it feels like a dilemma

I have learned that I have a wire resistance of 1.5 ohms. The question is if that combined with the 1.4 ohms coil is enough to protect the breaker points. What I did not get was the peak coil?

[George/Maine]

Gasoline
I think with the resistance wire is your problem.
If you run just the wire and coil you will be ok
9 at coil and rest at wire resister must be about 3 volts.
Story my 39 was changed to 12 volt and had a resister and coil.
would start ok but stop and get gas and was very hard to start.
When I was rewiring the car 39s have a resister under dash .5 ohms.
The .5 ohms resister was in use drawing the voltage down to coil.
Lets say 2 amps x.5 ohms=1 volt taken for coil makes for hard starting.
So you are trying to use 2 resisters only need one.
Its a series circuit has to add up the battery voltage.

[B_man_Al]

Hi George ...

I just did the experiment I suggested to you in post 76 with my model B, 1.5 ohm ballast, 1.5 ohm coil. Here's what I got using a digital multimeter.

1-Ignition off: V across ballast measured = 0 V
Comments - makes sense, as no current flowing

2-Ignition on, points open: V across ballast measured = 0V
Comments - makes sense, again as no current is flowing

3- Ignition on, points closed , engine off: V across ballast measured = 6.3V
Comments - makes sense, current is flowing and is 6.3V/1.5 ohms = 4.2A

4- Ignition on, engine running, points pulsing : V across ballast measured = 2.3V
Comments - If the voltmeter was reading correctly, and could read the peaks, it would read higher than case 3 by about 16% because of the increase in battery voltage from 12v to 14v. This would make it 7.3V instead of the measured 2.3V.

Thus the real coil current is about 7.3v/1.5 ohms=4.8A. This is what you would actually see if you made the measurement with an oscilloscope

However because of the averaging going on, there is a large error in the measured voltage, leading to the conclusion that the current is only 2.3v/1.5 ohms = 1.5 A. rather than 4.8A as calculated above.

Hope this helps to confuse the discussion some more :-)

[B_man_Al]

Gasoline ...

Thanks for your kind words !

In your original configuration, .7 ballast, .7 coil, and a wiring resistance of 1.5, the "engine off" current would be 12/(1.5 +.7+.7)=4.1 A.

This would increase by 16% to 4.7A with the engine running due to the ratio of 14v/12V.

The question then becomes is this sufficient current for that particular coil? If it is intended to work with only a .7ohm ballast, the peak current would be 10A with the engine running (14v/(.7+.7) . If this is for a 6V coil and ballast combination it should be fine without the "loom" resistor. If however this is intended for 12V operation, the points will surely burn at 10A pk.

From where you are now, ( 1.4 ohm coil, .7 ballast + 1.5 loom, ) the points should be happy either with or without the .7 ohm ballast. If you go through the same experiment in post 76 you should be able to determine all the voltages and currents involved with your setup.

[Gasoline]

Thanks, I will do that test tomorrow.

I should also mention that there were a 1.4 ohms coil and a 0.7 ballast resistor when I bought the car. When the car died that time on the highway (4 years after I bought it) I changed to a 0.7 MSD coil and a 0.7 resistor. It worked fine for 3 more years and then it happened many times this summer, during very hot summer days.

So to change to 1.4 ohms coil and skip the external resistor is more or less going back to the original setting and taking it a little bit further. I did not know that coil could have different ohms untill last week. At some point I think there has been a breakerless setting on this car. There is a lot of wires that are not really going anywhere.

[B_man_Al]

Attached is what you should get for voltages and currents for the 12v, engine off case with R loom=1.5, R ballast = .7, R coil = 1.4. If you want other cases let me know.

[Gasoline]

Thanks for all the support. I have two more questions:

According to MSD, the resistance is suppose to increase in the 0.7 ballast resistor (some sources say up to 1.4 ohms) when the engine is hot. How does that effect my voltage? (Perhaps you already explained this and I did not quite get it?) What would happen if I put in a 1.4 ohms ballast resistor instead of the 0.7, combined with a 1.4 ohms coil and kept the 1.5 ohms "wire resistance"?

The only thing that I changed on the car this year was to a leaner air fuel mixture since I had to high CO. Bubba wrote something that rich air fuel takes less and lean air fuel takes more voltage. Could this affect the "voltage need" in my car?

[George/Maine]

What coil do you have MSD 8203 ,
calls for a .8 OHM resister MDS coils 5 6 7.
If you put a 1.5 in stead of .7 plus wire 1.4 ohm that is the same as 2.9 total
if you had 2 amps that's about 6 volt only 6 left for coil.
more resistance is less amp.
so 2 amp .8= 1.6 leaving10 volt at coil
so 4amps.8=3.2 leaving 8.8 at coil.
(AS I said lose the wire ohms) and use what they said .8ohms/.7ohms.
Ask msd if its ok to use a wire resister with there .7ohm resister. that's a total of 2.2 at 2 amps thaths 4.4 = 7.6 ,4 amps is 8.8 leaving 3.2 volts at coil.

[B_man_Al]

As requested, for .7 and 1.4 ohm ballast ... slight modification on the first one from post 82. Current drops from 3.3 to 2.8A with ballast change

[BUBBAS IGNITION]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by b_man_al

as requested, for .7 and 1.4 ohm ballast ... Slight modification on the first one from post 82. Current drops from 3.3 to 2.8a with ballast change

good job on the charts , can we see one with a 12 volt, 1.5 ballast and a 1.5 coil ????

Thanks

[B_man_Al]

AS requested for 1.5 ohm ballast, 1.5 ohm coil, and no loom resistor. Added engine running case with points closed for peak voltages and currents. These need to be averaged by the dwell to get average voltages and currents.

[Gasoline]

This is great and easy to overview!

Can you post one with 12v, 1.5 ohms loom/wiring and 1.4 ohms coil and no ballast? (Perhaps, you already did this and I apologize if I missed it).

It seems like voltage to point is the same (0.1v)? What would be the maximum volt at coil and still have 0.1v at points?

[B_man_Al]

Ideally the voltage at (across) the points would be zero, if they were a "perfect" switch, with 0 ohms resistance. The coil voltage will not impact the voltage at the points significantly. I put a max of 0.1 volts to indicate that they are not badly pitted and have not become high resistance.

For instance if the points had 0.1v across them, with 4A flowing through them, the contact resistance would be 0.1/4=.025 ohms (25 milliohms) which is still pretty low. I am reading about 0.03 V on mine at 4A = 7.5 milliohms.

The lower the better. If you see this voltage creeping up to a volt or so over time, the points are likely ready for a good cleanup or replacement. Maybe Bubba can comment on the points numbers.

Here is the request slide with no ballast. The numbers are virtually the same, as the ballast has been replaced with the loom, but the totals are the same

[B_man_Al]

Here's the requested slide

[Gasoline]

Many thanks!

So according to this it would do no harm to the points and therefore it would be ok to skip the ballast resistor?

I will do the test as soon as I get my analog multimeter that I bought on ebay.

[B_man_Al]

Looks fine to me. Be sure to check the actual numbers with measurements to be sure.

With the engine off, the dissipation in the loom resistor will be about 25W (6.16V x 4.1A) …. That’s quite a lot of heat. How long is it, and where is it located? Is this an original part on the car, or an add on?

With the engine running, the power will be reduced to around 14W average because of the points opening and closing.

[Gasoline]

Hello again!

I got my analogue multimeter and it measured 8.2 volt on the positive side of the coil during idle. I am satisfied with that and therefore I am gonna keep the ballast resistor. The car is also running great.

However, I do wonder: Would it make any difference, performance wise, if there were 7, 8 or 9 volt at the positive side of the coil? For example under load?