Bypassing ballast resistor?

[Captain Obvious]

11 hours ago, w3wilkes said:

Is this true across the board? Would it also apply in the case of a ZX dizzy in my 12/71 Z?

From 74 through 77 they used a 0.5 Ohm coil and a 1.3 Ohm ballast resistor. Then from 78 through 83 they used as 1.0 Ohm coil and no ballast resistor, but they also put an "on-purpose" coil current limit built into the ignition modules.  Pre-78 modules had no such feature.

So Datsun wanted the 74-77 modules to be paired with a 1.8 Ohm resistor (except when cranking in START), and they wanted the 78-83 modules to be paired with a 1.0 Ohm resistor. I assume those pairings were somewhat derived through experimentation and analysis at their end.

So I'm no ignition expert, but here's my read getting to the meat of your question.... "Is it OK to run the ZX matchbox module (which was intended to be paired with a 1.0 Ohm coil) with a 71 coil instead?" I just took a look at the 72 FSM and it says the coil resistance is 1.6 Ohms. Using a 1.6 Ohm coil with the ZX module would result in the coil current being lower than as-designed, but if it runs OK and doesn't break up at higher RPM, then I'd let it be.

[Captain Obvious]

11 hours ago, chaseincats said:

Interesting, I wonder why Datsun didn't do that from the start...

Didn't do what from the start? The current limiting? I'm thinking that as technology progressed and emissions and performance requirements got harder to achieve, they made the modules better. It takes a couple more components to do the current limit and those components cost a couple pennies.

Looking at the insides of the modules, you can see the transition of the development technology from early seventies to late seventies. The early ones are metal can transistors on a PCB that was clearly laid out and taped by hand. And then by 77 they were using plastic case transistors on a CAD digitized board. The technology of both the parts used and the tools used to design that kind of stuff was moving VERY fast. Kind of a transition period in time.

[chaseincats]

17 minutes ago, Captain Obvious said:

From 74 through 77 they used a 0.5 Ohm coil and a 1.3 Ohm ballast resistor. Then from 78 through 83 they used as 1.0 Ohm coil and no ballast resistor, but they also put an "on-purpose" coil current limit built into the ignition modules.  Pre-78 modules had no such feature.

So Datsun wanted the 74-77 modules to be paired with a 1.8 Ohm resistor (except when cranking in START), and they wanted the 78-83 modules to be paired with a 1.0 Ohm resistor. I assume those pairings were somewhat derived through experimentation and analysis at their end.

So I'm no ignition expert, but here's my read getting to the meat of your question.... "Is it OK to run the ZX matchbox module (which was intended to be paired with a 1.0 Ohm coil) with a 71 coil instead?" I just took a look at the 72 FSM and it says the coil resistance is 1.6 Ohms. Using a 1.6 Ohm coil with the ZX module would result in the coil current being lower than as-designed, but if it runs OK and doesn't break up at higher RPM, then I'd let it be.

So since he has a 1.6 ohm coil, he is missing 0.8 ohms off needed resistance or is that safe enough not to damage the TIU/ECU?

Any idea about the high pitched noise from the coil and quick spin of the starter?  It sounds like there's some interfernce somewhere or something?

Edited February 11, 2023 by chaseincats

[Captain Obvious]

2 hours ago, chaseincats said:

So since he has a 1.6 ohm coil, he is missing 0.8 ohms off needed resistance or is that safe enough not to damage the TIU/ECU?

Any idea about the high pitched noise from the coil and quick spin of the starter?  It sounds like there's some interfernce somewhere or something?

I'm not sure which "he" you're talking about at this point... If you talking about your buddy with the 75 using a 1.6 Ohm coil with the stock 75 ignition module, then I think he is only 0.3 Ohms off from stock, not 0.8.

The stock 75 coil was 0.5 Ohms paired with a 1.3 Ohm ballast. The result is 1.8 Ohms total. Is your buddy using a non-stock 1.5 Ohm coil instead of the stock 0.5 Ohm coil?

[Zed Head]

The ballast resistor is actually an early form of current-limiting.  Probably too slow and imprecise to allow lower overall resistance.  An interesting piece of technology.  Kind of a shame that everything today has been shrunk down to microelectronics and computer code.

https://hardwarebee.com/ballast-resistor/

p.s. after you absorb the concept of the ballast resistor you realize that you can't just use a higher resistance coil and remove the ballast and get the same result.  Pretty sure that I have been guilty of suggesting that in the past.

Edited February 11, 2023 by Zed Head

[chaseincats]

I’m with the car now and am noticing when they key is in “on” but the car not running maybe every 30 seconds all injectors will click at once.  This is baffling, any ideas?

[Zed Head]

You should describe the state of the car at this point in time.  Coil, ignition module, throttle body, any wires left hanging, etc. 

Is the coil still whining? Is that why you're standing there with the key on?  How many 30 second intervals have passed where you heard the injectors click?  Is it actually 30 seconds or just your guesstimate of time passed?  Are you sure that your friend isn't messing around with something in the cabin?  Does he have other odd devices wired in somewhere?

The car seems possessed. 

[Zed Head]

2 hours ago, chaseincats said:

maybe every 30 seconds all injectors will click at once.  This is baffling, any ideas?

Here's a possibility, that I understand in concept but don't know exactly how it would work.  The ignition modules have a feature designed to cut current after a certain amount of time fi the key is left on.  Maybe that is what is happening.  When the current is cut a spark happens and the injectors squirt.  Actually, the current would have to be cut three times for each click, so that would mean every 10 seconds.  You should be able to see it on a meter.

Of course, that suggests that the current comes back on again, so the feature is not one and done.  It's more like a setting on an oven dial.

The FSM says within 10 seconds and calls it a lock preventive circuit.

[Captain Obvious]

23 hours ago, Zed Head said:

p.s. after you absorb the concept of the ballast resistor you realize that you can't just use a higher resistance coil and remove the ballast and get the same result.  Pretty sure that I have been guilty of suggesting that in the past.

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. They also referenced a simple LED circuit with a fixed resistor being used as a "ballast resistor" in the circuit. So it seems that a normal fixed resistor can be a "ballast". Same with the fan example.

Granted, ballasts that are designed to purposefully change their resistance as the temperature goes up is a thing. And active ballasts like they use in fluorescent lights are clearly a thing too. But those are specifically designed to change their resistance as the current through them changes.

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 article seems to be a modified version of this page. Not sure which came first, but this one is (slightly) better written? 
https://www.electrical4u.com/ballast-resistor/

[chaseincats]

36 minutes 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. They also referenced a simple LED circuit with a fixed resistor being used as a "ballast resistor" in the circuit. So it seems that a normal fixed resistor can be a "ballast". Same with the fan example.

Granted, ballasts that are designed to purposefully change their resistance as the temperature goes up is a thing. And active ballasts like they use in fluorescent lights are clearly a thing too. But those are specifically designed to change their resistance as the current through them changes.

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 article seems to be a modified version of this page. Not sure which came first, but this one is (slightly) better written? 
https://www.electrical4u.com/ballast-resistor/

A quick update for you guys:

We went and grabbed a coil/resistor from a friend yesterday and hooked everything up and noticed the car now (and apparently was slightly before) arching the spark from the coil to the body of the car and the spark plugs were getting pretty weak spark overall (and are BLACK).  The EFI is definitely working as the entire engine smells like gas and I went through every single test in the EFI bible and all the systems check out.  We then opened the ECU to see if anything was burned out from the extra power when we didnt use the ballast resistor and it looked fine.

The plan now is to take the ballast/coil back to my pal and grab an e12-80 distributor and bypass the possibly fried TIU and use the 1.6 ohm coil the car had on it before that worked with the crane x700 ballast-less ignition module.  I will update you guys in the next few days but I'm happy as a clam that its a spark and not efi issue.

[Patcon]

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

[SteveJ]

44 minutes ago, chaseincats said:

A quick update for you guys:

We went and grabbed a coil/resistor from a friend yesterday and hooked everything up and noticed the car now (and apparently was slightly before) arching the spark from the coil to the body of the car and the spark plugs were getting pretty weak spark overall (and are BLACK).  The EFI is definitely working as the entire engine smells like gas and I went through every single test in the EFI bible and all the systems check out.  We then opened the ECU to see if anything was burned out from the extra power when we didnt use the ballast resistor and it looked fine.

The plan now is to take the ballast/coil back to my pal and grab an e12-80 distributor and bypass the possibly fried TIU and use the 1.6 ohm coil the car had on it before that worked with the crane x700 ballast-less ignition module.  I will update you guys in the next few days but I'm happy as a clam that its a spark and not efi issue.

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.