Bypassing ballast resistor?

[Zed Head]

1 hour ago, Captain Obvious said:

I'm unconvinced. That article (which I must say was very poorly written*) talks about the concept of a "fixed ballast resistor" which is what the ignition system uses.

It's hard to find scholarly articles on the internet because everyone is trying to make money off of them.  You have to pay to read them.  Even 60 year old articles.  $35 just to read a paper from the 50's.

I try to learn what I can inexpensively.  Here's an example, linked below with an image, of a crumb of knowledge that disappears when you click through.  Gotta love the Google machine.

I really should sign up for a course at the local college so that I can use their library.  Things like this drive me closer.

https://scholar.google.com/scholar?hl=en&as_sdt=0%2C48&q=ballast+resistor+coil+ignition&btnG=

1932!  Theory.  Who knows if it went in to practice.  https://digital-library.theiet.org/content/journals/10.1049/jiee-1.1932.0001

 

[Zed Head]

p.s. an aside, kind of - if the resistance is moved to the coil then the heat goes with it.  Something to consider.

 

p.s. 2 on the sparking - the fact that spark jumps to the body means that the ignition system is working correctly.  You have an insulation problem.  Keep the current inside until it gets to the spark plug.

 

p.s. 3 the other stated purpose of the ballast resistor - to allow proper current through the coil when the starter is creating a voltage drop.  If you replace the ballast with a high resistance coil you lose that current during starting.  In theory the engine should then be harder to start.

 

I'm just pulling out odds and ends.  It might be a combination of many things.  In manufacturing R&D they typically stop when it "works" and can go to market.  Many of the compex systems in automotive are fixes on top of fixes.

Edited February 12, 2023 by Zed Head

[Zed Head]

5 hours ago, Captain Obvious said:

I will dig around a little and see if I have a Z ballast laying loose around here. If I do, I will try to see if I can measure resistance changes with respect to temperature. I mean... Pretty much all things change resistance as their temperature changes, but I ought to be able to tell if the ignition ballast changes are "on purpose" or not.

That would be 'cool'.  I think that just watching current with time might be telling.  Or temperature rise at constant voltage.  Or voltage drop with time.  You know what I mean.  If there is a change then the rate of change is probably relevant.

You're probably right and I over-mystified the situation.  But I think that the other stuff I brought up is relevant.

It's an interesting subject.  Mopar had a dual ballast system on some models.  Not sure if one was for starting or if the other came in to play during operation.  Looks like maybe the ignition module controlled or switched the other side on when appropriate, according to this article.  Check out their igntion tester.  They even modified it later to test the ballast resistor.  How complex could it be!?   https://moparconnectionmagazine.com/gallery-mancini-racing-reintroduces-the-orange-box-videos/

 

 

[Zed Head]

Mopar's old video, from that link above, at 4:44 is interesting.  I'm learning stuff.  

 

[chaseincats]

8 hours ago, Patcon said:

If it's arcing from the coil to ground, that suggests to me the resistance of arcing is lower than the dizzy, plug wires and plugs combined. That shouldn't be so! That is where I would start. Possibly with a meter if I knew what resistance numbers I was looking for

The weird thing is we tried that, tried every plug wire we could and still got spark coming out of the coil

[chaseincats]

8 hours ago, SteveJ said:

Where specifically on the coil is the arc occurring? It suggests to me that it could be the coil wire is not seated properly in the well on the coil and/or the insulation on the coil wire is breaking down.

It comes out of the area where the wire gets plugged in regardless of if the booth is pressed on or not

[chaseincats]

3 hours ago, Zed Head said:

Mopar's old video, from that link above, at 4:44 is interesting.  I'm learning stuff.  

 

really interesting watch, thx

[Captain Obvious]

18 hours ago, Zed Head said:

 I think that the other stuff I brought up is relevant.

Absolutely. Don't misinterpret my skepticism about location of the resistance (AKA "ballast"). The points you're bringing up are good stuff and completely valid:

Yes, having the ballast resistance outside the coil will also keep the heat generated in that resistance outside the coil.

And yes having an external ballast resistor allows for the ability to short across that resistance during engine cranking which could help providing a healthy spark even when the starter current is dragging the system voltage down due to it's large load. If the current limiting resistor is inside the coil, you lose that feature.

I'm just thinking that if you've got a good enough ignition system such that you can still easily start the car even while the starter load is pulling the battery voltage down .and. you have dwell length in control in such a manner that you are dissipating a small amount of power in the coil, then it should not really matter where the resistance is. Either inside or outside the coil would be fine.

But getting back to the OP's application, I guess the question is "Does the 75 ignition module meet those two above criteria?"

I've never opened up a 75 ignition module. I've reverse engineered the 77 and 78 and done a bunch of poking around with the matchbox modules, but I've never opened up a 75. I would expect it to be similar to the 77, but I really don't know for sure. Maybe the 75 module design is weak enough that you DO need to defeat the ballast during starting, and maybe the dwell control is looser than the later versions of the module?

Clearly by 78 they thought the module was good enough that they could use an internal resistance and eliminate the external ballast.

[chaseincats]

4 minutes ago, Captain Obvious said:

Absolutely. Don't misinterpret my skepticism about location of the resistance (AKA "ballast"). The points you're bringing up are good stuff and completely valid:

Yes, having the ballast resistance outside the coil will also keep the heat generated in that resistance outside the coil.

And yes having an external ballast resistor allows for the ability to short across that resistance during engine cranking which could help providing a healthy spark even when the starter current is dragging the system voltage down due to it's large load. If the current limiting resistor is inside the coil, you lose that feature.

I'm just thinking that if you've got a good enough ignition system such that you can still easily start the car even while the starter load is pulling the battery voltage down .and. you have dwell length in control in such a manner that you are dissipating a small amount of power in the coil, then it should not really matter where the resistance is. Either inside or outside the coil would be fine.

But getting back to the OP's application, I guess the question is "Does the 75 ignition module meet those two above criteria?"

I've never opened up a 75 ignition module. I've reverse engineered the 77 and 78 and done a bunch of poking around with the matchbox modules, but I've never opened up a 75. I would expect it to be similar to the 77, but I really don't know for sure. Maybe the 75 module design is weak enough that you DO need to defeat the ballast during starting, and maybe the dwell control is looser than the later versions of the module?

Clearly by 78 they thought the module was good enough that they could use an internal resistance and eliminate the external ballast.

Where is the reverse-engineered info located?  I'd love to read that.

[Captain Obvious]

I started putting some of it here:
https://www.classiczcars.com/forums/topic/67864-ignition-systems-analysls/

But it kinda fell by the wayside?

 

[chaseincats]

Final update: We probably fried the TIU because it no longer sent spark timed properly and some cylinders never got spark after the fact (we tried flipping plugs, wires, etc but the box simply wasn't telling the coil to fire for cylinder 5 at least.

We swapped the car to a 280zx matchbox distributor and it started right up.

All that to say, do not bypass the ballast resistor.

[Zed Head]

Sounds more like the pickup coil / reluctor system in the distributor.  The TIU doesn't know which cylinder is which.  But the distributor does.