[Half-Inch Stud]

Listen-up. All 4 of my spare Reluctors tested backwards on Voltage spike polarity. I probably got all these from 7-Pin Module HEIs! 4- Pin Modules matter.

2 PMD looking, 2 Chevy Looking Via Green/White wire position, yet same Voltage sense:
Goes + When bridging mag field, Goes neg when breaking field. Regardless of CW CCW direction.

Observation: My 4-Pin Module prefers sparking with reversed Green/White, 4-for-4 in my test jig. Now wondering what polatity reluctor is in the 68 GTO.

Best I can do is REF Motorola Mc3334 Trigger in the Schematic. Looks correct but opposite of my 4 Reluctors. Who knows for sure what VOLTAGE polarity is correct?

Also, Who knows for sure the fragile magnet polarity for pontiac using a North-South Compass Standard?

[Formulas]

How does one quantify results of differing polarities on a 4 pin module in ones own garage?

A sun machine / oscilloscope illustrating secondary voltage values, test set up would be interesting

I have spare components all from 4 pin set ups but would like to replicate your test

[mgarblik]

Just been through some of this with the pick-up coils in the old TI GM distributors. With those units, the solid white wire would be considered + and the white/green tracer would be considered -. In an HEI unit, the solid white would be considered + and the green considered -. There is a running test that can be done to verify if using an MSD if that's what you are doing. I can expand if this helps in anyway.

[Kenth]

Thanks to Schurkey:
https://www.gmcmi.com/wp-content/upl...stributors.pdf

[johnta1]

And Horst Fiedler page on the HEI

HEI PDF

[Half-Inch Stud]

All very nice, but the link appear to LACK information on evaluating Reluctor polarity. Here is how i do it.

Reluctor has white (neg) and Greem (pos) wires. Connect your DMM (low voltage, manual range on DC Volts) to reluctor. Black to white, Red to Green.

Manually rotate the pole piece to align points; i see voltage goe Positive.
Manually rotate the pole piece to break points; i see voltage go negative.
edit: an .oscilloscope will show this, in a fancy way.

Seems to me the Reluctors from 4- pin module HEIs are opposite of reluctors from 7&8 pin module HEIs. Yet no visual difference in reluctors. Green/white swap position, but polarity is old vs newer. huh

[Ben M.]

Sure would be nice if someone could use an oscilloscope to capture some waveforms of the primary voltage and pickup signals to show what they're supposed to look like and what the effect of using the wrong pickup coil is...

[johnta1]

For the 4 pin HEI module, the Green wire is ground.
Don't know the other pins modules. The extra pins did different things.
The 7 pin is supposed to be all computer controlled, so it may need a computer to feed whatever it needs?
(doesn't matter the polarity)



Why use the 7 pin setup?
Why use any module, use a MSD box to run it.

[Half-Inch Stud]

This is all about what the 4- Pin Module wants/needs to see in the reluctor waveform.

My study shows there is no GND among the White & Green Module Lugs.
Rather there are resistor values for White to GND, Green to GND and White-to-Green.
Also, the dwell-expanding modules are the ONLY 4-pin modules we shall use. Cheapo aftermarket 4-pin modules lack dwell expansion

Evidence of dwell expansion can be done with dwell meter while dizzy operates, or simply at the module level you look for 0.7V or 1.1 Volt on the Reluctor Lugs with B+ applied. 0 Volt on the reluctor lugs indicates a cheapo constant dwell module that should be tossed in the creek.

So, My HEI test set shows the 4- pin module prefers the reluctor that goes Pos-to-neg. Goes pos when Mag Pole point come together, and goes negative when poles break away.
Documentations say the opposite. Except the Motorola MC3334 datasheet (which is the dwell expanding chip in the GM 466 4- Pin Modules of great lore.

So, fundamentally i even need to know what compass needle N vs S says is attracted to the PMD reluctor top, and then then the Chevy reluctor top. If I know the mag pole orientation for-sure, THEN i can sort the voltage polarity for each reluctor coil.

I'm most annoyed that GM HEI would have same looking reluctors, regardless of gree/white qire exit position from reluctor, yet can have opposite Voltage polarity based on VINTAGE, Green/white wires always go to module the same way.

[Half-Inch Stud]

As said before, yet more clear; the 4- pin module triggers much better for Green/white voltage polarity being correct vs opposite voltage polarity.

I should be able to flip the magnet (buy chevy becomes Pontiac and Pontiac becomes Chevy). Could get messy.

[Schurkey]

1. You're talking about the PICKUP COIL, not the reluctor. The reluctor is the iron/steel toothed wheel, connected to the distributor shaft, that spins inside the pickup coil.

2. Unless the pickup coil was manufactured wrong--or taken apart and then reassembled incorrectly--the electrical polarity should be correct. The magnet inside the pickup coil would have to be upside-down/backwards polarity, I think. So you could change the magnetic polarity by flipping the wires/bobbin, and the electrical polarity by flipping the magnet--I think. You'd have to be sure of reassembling the pickup coil so that all the pieces aligned/centered properly. Might require an assembly jig of some sort. I've never dicked with this.

The pickup coil provides an AC electrical signal, kind of a sawtooth pattern, or a "modified" triangle wave. The signal voltage should gradually increase (+) as the reluctor teeth and the pickup coil teeth become aligned; and then rapidly shift to a negative polarity as the two sets of teeth pass each other, Direction of rotation does not change this--as the teeth get closer they generate a positive-going waveform that dramatically shifts to negative-going as the teeth just pass alignment and get farther apart. The ignition module triggers on that sudden, dramatic, negative-going part of the waveform as the voltage passes "0" on it's way from + to -.

The pickup coil wires are color-coded White and Green. The module terminals are probably labeled "W" and "G". Proper electrical polarity is assured when the colors match. If the electrical polarity were reversed, yes, the module doesn't like it at all.

Proper MAGNETIC polarity is determined by the direction the wire is wound around the bobbin--or more-accurately, the direction the bobbin and wires are inserted into the pickup coil assembly. With the bobbin and wires "upside down" on some pickup coils, the wires have to be crossed to assure that the white wire connects to the W terminal of the module. Other than crossing the wires--still White to W, Green to G--MAGNETIC polarity has NOTHING to do with the electrical polarity. Magnetic polarity is important for not picking up interference caused by electro-magnetic radiation that would provide false "triggers" for the ignition module.

The "Chevy/Cadillac" (Yellow color-code) pickup coil has the shortest wires. The Pontiac pickup coil (clear, or no color code) has the longest wires. The Olds/Buick (Black or Blue color code) has wires that are in-between in length.

[Half-Inch Stud]

Originally Posted by johnta1

For the 4 pin HEI module, the Green wire is ground.
Don't know the other pins modules. The extra pins did different things.
The 7 pin is supposed to be all computer controlled, so it may need a computer to feed whatever it needs?
(doesn't matter the polarity)



Why use the 7 pin setup?
Why use any module, use a MSD box to run it.

4-pin module remain most superior to 7-8 pin modules for Reliable Street/Strip.
5-pin modules: one of the 5-pin designs allows a simple 10degree retard for cranking.
7- (8 includes a GND pin) pin module with BRE allows external 'puter pulse processing, or simple delay. gets funky, less Reliable.

MSD-6 is a CDI (capacitive discharge) which is differnt and not better than MDI (Magnetic Discharge). CDI can be as-good, or more than good enough; the Mark 10B and Mark10C CDI can be argued as better than MSD-6, yet all the CDis have shorter spark duration like 150uSec, where HEI has 1.5 mSec spark duration, for fouled plug firing, & high compression firing.
CDI stores higher energy 120 mJ in the Capacitor, but doesn't deliver all that energy as spark energy. CDI spark energy is around 30 mJ, a little more or a little less. HEI is 70-60 mJ spark energy across RPM due mostly to reluctor signal strength increase with RPM and 0.6-1 Ohm Primary winding.

So, ahem, HEI reluctor polarity gotta match what the module needs to see.

[Half-Inch Stud]

Originally Posted by Schurkey

1. You're talking about the PICKUP COIL, not the reluctor. The reluctor is the iron/steel toothed wheel, connected to the distributor shaft, that spins inside the pickup coil.

2. Unless the pickup coil was manufactured wrong--or taken apart and then reassembled incorrectly--the electrical polarity should be correct. The magnet inside the pickup coil would have to be upside-down/backwards polarity, I think.

The pickup coil provides an AC electrical signal, kind of a sawtooth pattern, or a "modified" triangle wave. The signal voltage should gradually increase (+) as the reluctor teeth and the pickup coil teeth become aligned; and then rapidly shift to a negative polarity as the two sets of teeth pass each other, Direction of rotation does not change this--as the teeth get closer they generate a positive-going waveform that dramatically shifts to negative-going as the teeth just pass alignment and get farther apart. The ignition module triggers on that sudden, dramatic, negative-going part of the waveform as the voltage passes "0" on it's way from + to -.

The pickup coil wires are color-coded White and Green. The module terminals are probably labeled "W" and "G". Proper electrical polarity is assured when the colors match.

Proper MAGNETIC polarity is determined by the direction the wire is wound around the bobbin--or more-accurately, the direction the bobbin and wires are inserted into the pickup coil assembly. With the bobbin and wires "upside down" on some pickup coils, the wires have to be crossed to assure that the white wire connects to the W terminal of the module.

1. Reluctor is really the assmbly: the pickup coil with mag pole piece. I separate-out the pickup coil and magnet and cup as having VARIATION.

2. oh yea, they vary in winding direction and which magnet pole is up. Correct with the triangle voltage wave. Thing is i observe the module triggering (coil firing a plug) better with the wires flipped. Indicating the reluctor polarity is wrongk. In fact i have 4 reluctors that are wrongk. Thinking occurred that these reluctors came from modern 7-8 pin HEIs which GM switched the voltage polarity (reluctor and 7-8 pinmodules)

[george kujanski]

Simply stated without math: Faraday’s law states that the voltage induced due to a changing magnetic field is opposite to the change.

So we have a coil of wire with a magnetic field. Assume the coil is not connected to anything. As the teeth approach, the field increases, inducing a negative voltage on one wire relative to the other wire. Since neither wire is referenced to any other electrical thing, the other end of the pickup coil goes positive relative to the first end. As the teeth move apart, the magnetic field decreases so the induced voltage reverses.
In the module, one end of the pickup wires may be connected to the common (ground) reference so the initial negative-going wire end or the positive going wire end may be more important to the circuit so reversing the wire connections take care of that.

The polarity of the magnet itself does not matter, as the teeth approach the same voltage appears on the wire ends regardless of the way the poles are arranged.

George

[Schurkey]

Originally Posted by Half-Inch Stud

I separate-out the pickup coil and magnet and cup as having VARIATION.

The only variations I'm aware of for V-8 engines/HEI distributors--beyond GM having multiple part numbers to fit various distributor housings--is the magnetic polarity and wire length, as described above, and in my photo posted prevously by Kenth; and some pickup coils are color-coded via molded plastic connectors, others by colored tyraps on the wires. Depending on the series of HEI, some have provision on the pickup coil assembly for a vacuum-advance connection; others have computer-controlled timing so no vacuum advance. None of this would change that white goes to W, and green goes to G on the module.

2. ...Thing is i observe the module triggering (coil firing a plug) better with the wires flipped. Indicating the reluctor polarity is wrongk. In fact i have 4 reluctors that are wrongk. Thinking occurred that these reluctors came from modern 7-8 pin HEIs which GM switched the voltage polarity (reluctor and 7-8 pinmodules)[/QUOTE]
I'm not in a position to argue this. However, I think it's unlikely. The positive-going waveform is a gradual increase, the negative-going part of the waveform is a dramatic drop. They used the dramatic drop instead of the gradual increase in order to get the ignition timing more precise--there's no ambiguity of that dramatic drop like there could be with the gradual increase.

I've heard of MSD spark-boxes that retard the timing about 14 degrees if the pickup coil is wired backwards electrically. Seems to me that the spark box acts goofy beyond the retarded timing, as if it were confused about when to fire. But I've never experienced this first-hand.

Point being, the only way they'd allow the pickup coil to have reversed electrical polarity is if the circuitry in the matching module required that reversed polarity. Whether Delco designed the 7--8 pin modules to require reversed polarity is something I haven't verified. Like I said...seems unlikely.

I'd bet my two cents on your test-bench having some anomaly that is giving you questionable results with regard to pickup coil electrical polarity. For example, what do you mean by "i observe the module triggering (coil firing a plug) better with the wires flipped." Define "better". Do you mean stronger spark? More reliable spark? Different spark timing (advance/retard)? Something else?

Originally Posted by george kujanski

The polarity of the magnet itself does not matter, as the teeth approach the same voltage appears on the wire ends regardless of the way the poles are arranged.

Thanks for that. I had a devil on one shoulder telling me it made a difference, and an angel on the other saying it didn't. I couldn't decide which one to believe.

I'm sure I read--on a forum on the internet, so of course not a reliable guide--that someone took his pickup coil apart, and reversed the magnet; this resulted in some sort of trouble. Perhaps just internet lies.

I've got some direct experience with BROKEN magnets for the pickup coil; I had a high-speed misfire that got worse and worse (progressively lower speed) until the engine died at idle and wouldn't re-start. Of course, hundreds of miles from home. The local GM dealer installed a new mainshaft in the distributor (small-cap HEI, magnets and reluctor integral with the shaft) Problem solved.

[Half-Inch Stud]

Schurkey, Goodness, and "quote parsing" not needed. New info;

I read your "Dizzy and HEI Installs" article and have the following comments:
1. Very good photos. Very well done there.

2. "Ported Vacuum is just Manifold Vacuum that is shut off at Idle. Try either and decide what the engine likes". Excellent clarity point for the hearing impaired.

3. I put my 100/140 Watt Weller gun to my relutor setup and full force triggering (i was impressed) yet worked with either polarity into the Module ( i got dismayed).

4. "Put 12 volt Probe on the G terminal. Should spark when removed." I did not do that and trust that will work on all good 4-pin modules. I may try that to all my (4,7,8-pin) modules to verify Voltage Polarity desired versus folklore.

Useful Dizzy rotation Eval i did to some Reluctors: "Make" is Pole posts aligning. "Break" is pole posts separating but not re-aligning with the next pole posts.

Green/White wires proper into 4-Pin Module: Slow & Fast "Make" Sparks!. Slow & Fast Break: Nothing. very nice and supports "dramatic drop" in voltage for no movement after "Make" cant make no more.

White/Green wire wrongly into 4-pin module: Slow & Fast "Make" nothing. Slow "Break" nothing. Fast "Break" sparks! not assuring for slow Cranking.

From this eval alone, I think the Reluctor Voltage Polarity is correct for Sparking/Triggering on "Make".

My next action is to dig-out my North-South "Standard" to check or make a good compass. Right hand rule applies. Then check each Reluctor for magnet sense. Then make all the reluctors Pontiac Magnetic sense for sure. And Spark on "Make".

The $1 each china compases for kids will flip magnetization when NIB magnet strength is used to interrogate them. very uncool craaaap they exported.

Sidenote: i have a new-looking chevy reluctor (Dizzy Polepiece looks aftermarket or cheapened) which would drop Triggerings on the slow "Make". Well that would be bad. It has a 964 Ohm winding, (not the usual 784-790 Ohms) and puts out a lower AC voltage, about half voltage of the GM Pontiac and Checy Reluctors.

[Half-Inch Stud]

Originally Posted by george kujanski

Simply stated without math: Faraday’s law states that the voltage induced due to a changing magnetic field is opposite to the change.

So we have a coil of wire with a magnetic field. Assume the coil is not connected to anything. As the teeth approach, the field increases, inducing a negative voltage on one wire relative to the other wire. Since neither wire is referenced to any other electrical thing, the other end of the pickup coil goes positive relative to the first end. As the teeth move apart, the magnetic field decreases so the induced voltage reverses.
In the module, one end of the pickup wires may be connected to the common (ground) reference so the initial negative-going wire end or the positive going wire end may be more important to the circuit so reversing the wire connections take care of that.

The polarity of the magnet itself does not matter, as the teeth approach the same voltage appears on the wire ends regardless of the way the poles are arranged. George

Right-hand rule makes sense of that. thatsa pun son, a funny.

[1968GTO421]

I confess that I am lost in this thread. But I'll keep re-reading it as that is how to learn. Electronics was never my strong suit and here's a geat opportunity to learn more about ignition electronics. So far It sounds like the HEI is more powerful than an MSD but there is still more here than that. Thanks all.

[johnta1]

The MSD 'probably' has the same 'power' but its forte' was the Multi-Spark Discharge. Meaning many high power sparks per one cylinder firing.
The HEI only does one spark per cylinder firing. (like points but stronger)

[Schurkey]

Originally Posted by Half-Inch Stud

3. I put my 100/140 Watt Weller gun to my relutor setup and full force triggering (i was impressed) yet worked with either polarity into the Module ( i got dismayed)

The inducted voltage into the pickup coil will be based on the AC voltage going through the soldering gun. The AC voltage will be a sine-wave or close to it.

The module is actually expecting to see that "sawtooth" wave; but a sine wave is close enough that it works to trigger the module.

Given that the soldering iron is creating a sine-wave signal to the module, it's not surprising that reversing the wires has no effect. The sine-wave is symmetrical; the sawtooth wave isn't. What works with the soldering iron on the test-bench might not work as well with a rotating pole-piece in real life.