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Discussion Starter · #1 ·
In a conversation months ago I promised to make a HEI Module/TFI Coil Hybrid ignition for a friend. In the past couple of weeks procrastination was set aside and progress has been made.

The Jeep in question is 197X I6 still running a Prestolite distributor but there is a newer style DuraSpark distributor waiting to be installed. Also on hand will be Ford's large cap, rotor and better plug wires.

Went out to my personal salvage yard looking for a wiring harness to use and this is what I found (click on any picture for a large version):







The rusty old coil, AMC V8 distributor guts and Stealth HEI in a DuraSpark box are just props for the pictures. The point of the pictures is simply that this 197X wiring harness isn't in very good shape and it was made with 16 and 18 gauge wire. Some of the insulation was old and brittle. The wiring came with a AMC 360 from a FSJ but I'm not really sure of the year.

Looking to make something simple, cheap and reliable for a friend. I decided to toss all of the old harness except the distributor connector.



If you need to solder new wires to old wires strip and clean the old wire best you can with isopropyl alcohol or even brake parts cleaner, then use soldering paste flux. The flux will boil off the oxidation and allow the solder to adhere. Always clean solder joints with alcohol (or brake parts cleaner) after they they cool and before insulating.



Want a completely weather tight solder connection? Apply a light coat of Scotchkote and then heat shrink tubing (Polyolfin).



So there is a harness to the distributor. Also need coil wiring.



Shown above are the two TFI coil pigtails that you will most likely find. Both are made with 16 gauge wires. The extra green wire is for a Tach connection, but not a stock 198X CJ Tach.

Now there are two fairly simple wiring harnesses.



So what can we do with that? Ahhh put it all together with just a few other components and see if it works? Sure why not!



Well the darn thing starts right up and runs fine. But there are two issues.

First issue, heat. The little aluminum box got pretty hot real fast so a Slot One Intel Processor heat sink was chopped up and installed. Silicone heat sink compound was applied between the HEI Module and the box and between the add on heat sink and the aluminum box. When you get down to it the box just didn't have enough surface area to dissipate the heat.



Still one issue hanging!

There is a fuse-able link installed as the power source for the HEI Module and TFI Coil. Nice big ring tongue that connects to the battery cable on the starter solenoid.

Also the contacts of a 30A relay in line with the fuse-able link to power the ignition. The relay coil is connected to switched +12 and ground.

How about a little math and why the big wires in the above pictures are 14 gauge?

Anyone know what that other issue is??

/ubbthreads/images/graemlins/40BEER.gif
Dale
 

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why are you re engineering this issue...just go to JYGs site and get the prints, my setup now has bout 1500 miles on it(i have yet to put in the supply relay /ubbthreads/images/graemlins/blush.gif, but the briggs and stratton key switch is ok so far lol), gave the system a good 75 mile high heat index test last week(bout 102 deg F, heat index of around 110--very rare in NH), did great, the ss box i made for it stayed nice and cool
 

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It sure would be nice to have a cold day like you had once in a while just to break up the monotony.
118 today.



What is your provision for mounting the box? The "way" and "where" the box is mounted can provide additional heat sinking.

Where is your ground?

Why the small wires - you do realize the system flows about 10 amps instantaneously? Remember, it's not a purely resistive load.

Power to the module can be small, but from + batt to coil to module to ground is the high current path.

Remember too - the bottom end of the coil secondary is tied back to the + side of the primary internally in the coil. So the secondary's current path is through the plug to ground, through the batt to the batt + and back to the coil through those small wires. People forget the return path of the secondary.
 

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[ QUOTE ]
you do realize the system flows about 10 amps instantaneously?

[/ QUOTE ]

Hmmm. I wonder if a proper cap could average out the flow. At 4000 RPM the frequency for a six would be 12khz. Any idea what the duty cycle is? Maybe you don't really need bigger wire.
 

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mounted the module to a 1/2' thick aluminum plate(about 5x7"), changed plan and mounted that to a larger(about 7X9 or so) mounted that assembly to the firewall on dist side of motor about even w/ top of head, used studs out from plate to mount the cover on and made a bracket for the coil that mounts off the head where the can style coil mount was, but hangs a bit lower to provide clearance for the large cap etc....

not worried about the heat so much, been driving hei v8s most of my life and i figure the inside of a chevy dist is running in the 185-230 degrees F range its' whole life

pulled the cover right when i got home and i could leave the back of my fingers on the module all day(estimate it was around 130-140 ish F

and yes...i will rewire per the relay discussion of a couple weeks ago, the timing of that thread was right after i finished fabbing things up and dangitall i wanted to drive the thing sometime this year/ubbthreads/images/graemlins/smile.gif
 

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Jim - Yes a huge capacitor would do it - but it would have to be HUGE! (And fed with the big wire too.)

HEI 6 cyl Dwell at 3000+ RPM would be about 45 degrees - or 45/60 = or about 66% duty cycle.

Best, easiest, cheapest, simplest to let the battery feed it unrestricted by the wire's resistance. (The battery is like a huge capacitor.)

The small wire will work, but it's resistance is limiting the potential. Thus the need for a relay, but even a relay needs to feed it with a larger wire.

The high energy in the HEI is because of it's ability to carry more amps - best to let it do it's job.



If it doesn't burn your finger it's running cooler than it does in a stock HEI distributor.
Uh, that's cool to be that cool.

Protect it from water splashing on it - hot then suddenly cold could be it's demise. That's why I like the "Stealth HEI" - the HEI built into a Ford/Jeep's stock aluminum box. Besides protection, it's probably not detectable during a routine smog check.
 

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I'm just wondering why you used a fusable link in the power line. It seems it would be hard to replace in the field were as an inline fuse would work quite nice.

The only other thing is what do you gain soldering a heavy gauge wire onto a smaller gauge. Difference in ohm/ft might of dropped a tiny amount.
Think how much water flow would improve if you connected a 3/4" pipe onto a 1/2" pipe.

I'm thinking that little 2" of wire is going to get plenty hot if there is any serious current demand. But maybe there won't be. You would have to measure across the thinner wire to see how much voltage drop you are getting.

But I might be all wrong about this. Being a little anal and cheap, I have been known to remove the terminal from the plug and remove the old wire and solder the heavier gauge wire directly to the terminal.

Anyone know were you can get new automotive terminals? I doubt if companies like painless make thier own.
 

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[ QUOTE ]
about 66% duty cycle

[/ QUOTE ]

Well, if it's flowing 10 amps 66% of the time, and if a cap could even out the flow perfectly, you'd be drawing 7 amps through the stock 14 gauge wire, which should be OK. They make some pretty small 1 farad caps these days, but I would guess that they're too slow to do the job. It would have to be a big electrolytic, I guess.

Only thing to be said for my scheme is that a cap is inherently more reliable than a mechanical relay, but in the underhood environment, who knows?
 

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Yes, it's like a small pipe in the middle of a big pipe - sorta.
Resistance depends not only on the cross section but the length. A short piece is better than a long one, but not as good as just a big wire the whole way. (Less worse?)

The soldered connections are often another source of resistance. Crimp good, then solder.


Car Quest has the ability to order OEM connectors - even the strange ones. Ask to see their catalog.
 

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[ QUOTE ]
jeepnut_nh wrote;
"why are you re engineering this issue...just go to JYGs site and get the prints"

[/ QUOTE ]

If he comes up with his own answers, Right or Wrong, at least he's learned something...
---------------------------------

[ QUOTE ]
Jim_Lou wrote;
"Hmmm. I wonder if a proper cap could average out the flow.

[/ QUOTE ]

[ QUOTE ]
RRich Wrote,
"Jim - Yes a huge capacitor would do it - but it would have to be HUGE! (And fed with the big wire too.)

[/ QUOTE ]

Yup, you could, but you would be up to an 8 gauge wire or larger, would need a second dedicated ground to the module, and will use at least one capacitor that are about $35 each.
2 or 3 of the fast discharge types would be better than one really large one, but I encourage doing the testing yourself.
(Keep your caps under Lexan, they have a tendency to explode when mismatched)

10 gauge wire to the coil and from the coil to ground is enough to get 95% or more of the usable spark energy out of the coil with the GM HEI doing the switching.

I'm still not happy with the GM HEI's switching times or it's leaky design, but the generic GM HEI is out performing the generic Ford modules now.
It didn't used to be that way...
 

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I'm going to have to crack open a few books because I was thinking that is the short wire would have less surface area to dissipate the heat from the loss were as a long piece of wire would allow it dissipate it over the whole distance.

But maybe the length has a bigger effect than the cross section as far a current capacity.

There is just a feeling about running heavy wires in small wires that doesn't seem right.
 

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Think about how a fusable link is made - a small wire fed by bigger wires.
The slightly more resistance heats the link till it melts.


He He - the capacitors.
Remember during the dwell time the capacitor would be dumping it's charge to the coil/module. So the 10 would be fine there.

But during the "off time" it would have to do it's charging for next time. Since all that energy has to flow to recharge the capacitor during only 33% of the dwell time, the feed wire from the battery would have to be bigger yet!

Like JYG said - 8 would be appropriate there.

And there's another way - mount a big diesel generator right next to the module.

Sure is gettin complicated!

Why not just do it right from the start?
 

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[ QUOTE ]
Think about how a fusable link is made - a small wire fed by bigger wires.
The slightly more resistance heats the link till it melts.

...

[/ QUOTE ]

This is what I mean. Big wires leading into little wires turn little wires into fuses. unfortunatly, there is no plastic or glass surrounding these "fuses" so they just burn off the insulation as they melt taking the sourounding insulation off exposing more wire until 'poof' .
 

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[ QUOTE ]
Big wires leading into little wires turn little wires into fuses. unfortunatly, there is no plastic or glass surrounding these "fuses" so they just burn off the insulation as they melt taking the sourounding insulation off exposing more wire until 'poof' .

[/ QUOTE ]

Or... the Lucas Theory of Electronics... /ubbthreads/images/graemlins/grin.gif
 

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If you are going to hang a rack of discharge caps on the fender, why not take the next logical step and pump up the output voltage to the coil up to about 600 volts?

Put in some 'digital square wave' fast switching transistors and use a bobbin wound ignition coil and call it a capacitive discharge ignition ...
OH, wait, MSD already did that!/ubbthreads/images/graemlins/tongue.gif I'm getting ahead of my self!
-------------------

Seriously,
A proper 10 gauge wire feed seems to be the answer for increasing the output of the ignition coil.
(not scabbed together wiring, but with the proper connectors and properly soldered connections on virgin copper wire instead of alloy wire...)

We are stuck with stock modules that just don't switch as fast as they could, so the magnetic field is slow to build, and slow to collapse.
Output could be much higher if the switching were cleaner, but we have to use a stock module of some kind...
The HEI module can't switch any faster, and you would have to use a digital type switch to cut current to the field to make the coil output any stronger.

Adding caps to the system raises the failure potential by adding components that can fail,
AND,
Raises the "Difficulty To Engineer" factor.
You are talking about non stock parts also, something you can't walk into a discount parts store and pick up./ubbthreads/images/graemlins/frown.gif
--------------------------

I encourage testing!
Lets keep it where 'Average Joe' can do this and it won't take three degrees from MIT to figure it out.../ubbthreads/images/graemlins/smile.gif
 

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Yup ---- KISS!

That always seems to work best.



But wouldn't it be fun to walk into an AutoChinaZone store and ask the ex-burger flipper for a pair of 10 Farad 500 volt capacitors?

His pimples would pop!
 

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Discussion Starter · #17 ·
OK, it's still my thread isn't it?

I did mention that it starts up fine and runs fine didn't I?? There is no difference to the "Stealth HEI" that I put in a year or so ago. I don't have a Dyno and exauhst gas analizer to fine tune this.

I have a real problem with the relay. /ubbthreads/images/graemlins/blush.gif

Seems like a safety issue equal to having brakes and seatbelts.

Guess that any club fisted bozo would just install a "Kill Switch"... but that's not good for me, I want the engine to stop when I turn off the key switch.

Every relay that I have put in line with the ignition contacts powers the coil enough that the engine won't shut off when I turn off the key switch.

There must be some simple way???
 

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Strange, it shouldn't do that.

You do have the ignition switch powering the coil of the relay and nothing else?

And the contacts should bring power to BOTH the + side of the coil AND the module power lead. The opposing contact should be a big wire to the battery +.

Yup, still your thread, for that matter, still anybodys.
 

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Yup, still your thread!
So when you figure this 'Relay Problem' out, post it.

Or do you just want to give in and ask for the answer to your 'Relay Problem'?
So when you post a thread with my name asking for help, I'll respond (...maybe...)

I mean, I don't want to butt into YOUR THREAD or anything...

After all the times you hijacked other peoples threads just so you could try and (unsuccessfully) show off, I'm surprised you have the gall to post something like that...
-----------------------

After all the grief you gave me, and come to find out you can't wire a basic ignition system or relay!

I really should jump on your like you did me, but I've just plain got other things to do...
 

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[ QUOTE ]
....

Still one issue hanging!

There is a fuse-able link installed as the power source for the HEI Module and TFI Coil. Nice big ring tongue that connects to the battery cable on the starter solenoid.

Also the contacts of a 30A relay in line with the fuse-able link to power the ignition. The relay coil is connected to switched +12 and ground.

How about a little math and why the big wires in the above pictures are 14 gauge?

Anyone know what that other issue is??

/ubbthreads/images/graemlins/40BEER.gif
Dale

[/ QUOTE ]

This is confusing and probably why your engine keeps running.

Does your fusable link run from the battery terminal on the starter solonoid to the relay contacts or directly to the ignition module?

How exactly are the relay contacts conected to the "Ignition" Do you mean the ignition coil or the wire supplying power to both the ignition coil and the ignition module.
 
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