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post #1 of (permalink) Old 01-02-2005, 03:35 PM
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RRich,LEVE,others... : Dspark Ign Mod Quandary....

Hey guys,

There's an interesting research point J Strenk has come across with some Oscope testing on his Ign Mod. Just wanted to get you guys opinions on it. Your thought in the past have proven both capable and beneficial. Without doing a whole lot of copying and retyping, I'll just link the thread. [url Clicky - JU Thread.

For some reason the period of 0 volts on the coil - term for the Dspark ignition module shows greater than the HEI Ign Module, though the dwell angle, and, consequently, spark duration, is less. What do you all think we should expect to see, and why the results he's getting?

Thanks fellas..
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post #2 of (permalink) Old 01-02-2005, 10:31 PM
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Re: RRich,LEVE,others... : Dspark Ign Mod Quandary....

I saved a link to that thread on JU... Interesting that he used an OScope, I have one. Will think about it while others post up.

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post #3 of (permalink) Old 01-03-2005, 12:49 AM
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Re: RRich,LEVE,others... : Dspark Ign Mod Quandary....

Interesting -- but a real pleasure to answer this one -- since he's got actual scope patterns - sure makes it easy to see what's going on.
I don't know how to post on that board, so I'll have to answer here. Maybe someone can direct him here? Or me there?

The Duraspark -- he's looking at the older type Duraspark - the original Ford type that Jeep used, not the DuraSpark II that's comparable to the GM HEI. Apples vs. celery.
The Duraspark he has is only an electronic switch, replaces the points, but does not create any higher energy. And I think he has the resistor still installed - can't tell for sure with the pattern.
Dwell will always be about 30 degrees on an 8 cyl, about 45 on a 6 on those. It does NOT have the variable dwell like GM.

The humming - he's got it, a low battery can cause them to false trigger - the hum. If he was to touch the coil wire while it hummed -- he'd get a good jolt! It's making spark constantly like that. If he was to take out the resistor it would still do it, but at a lower battery voltage than with it. Normal -- (I hate those old Ford ignitions if you can't tell.)
(Interesting -- the Ford Model T used a constant spark -- the coil wire was always at high voltsge all the time. When the rotor got close the the correct tower, it lit that plug. It continued to fire that plug till the rotor got close to the next tower, then it fired that one. It worked! Hmmm, guess you could say it was the original multiple spark discharge system! But it's not anything like an MSD.)

And -- I suspect that the wire that's feeding the module, or feeding the ignition switch is small -- it should be a at least a 12 gauge, a GM HEI prefers a 10 gauge to feed it.

And, as my mind rambles to the wierd and obscure -- Could also be something off the wall -- the source of the 12 volts to the coil and module through the ignition key -- make sure it's not getting it's power through the CVR -- the Constant Voltage Regulator for the gauges. The CVR switches on and off constantly to regulate the voltage -- can drive a module nuts! He He -- Don't ask! But yes! Duh! It's easy to grab the wrong source.

The "starts like it's at 20 degrees," "bucks like crazy." Yes, it's spark during starting is way too early. Since it's "Humming" it's constantly making a spark - all the time. When during cranking as the rotor turns close enough to let the spark jump to the tower, it fires that plug -- but since it's not a timed controled spark it ignites the mixture waaaaay too early. (Just like the Model T.)
Once it starts, the starter is no longer dragging battery voltage down, and the alternator brings the voltage up, it stops humming (false triggering) and runs like normal. Makes it kinda confusing, but it's simple.

If you look close on any of the patterns you can see the "downward" square portion - that's when the Dwell time starts - coil charging time. Just to the right of it at the end of the straight line where it jumps upward is the end of the Dwell time (coil charging time) -- on the Ford Duraspark. That time frame - in degrees of rotaton, remains constant.

On the GM - if you look close you can see a small "blip" before the next firing. That's the current limiter working - it keeps the coil from "overcharging" and burning up. A Dwell meter actually measures the dwell time as the time "in between" the 1st square (module turn-on) to the current limiter "blip." At idle the GM HEI will show a dwell time of about 12 degrees, as you rev it, Dwell increases to max - 30 degrees on a 8, 45 on a 6.
Absolutely normal. I can also see he has no resistor in the circuit -- good!
With the HEI, charging time is NOT based on degrees of rotation, but on actual available time in milliseconds. But remember, Dwell is measured in degrees. The faster the rotation, the less time available in real time - milliseconds.

!!! Remember the Ford Duraspark uses a resistor to limit the current, the GM does not use a resistor, instead it has a built-in electronic current limiter to keep things from melting!!!

Gee - I wish everyone could put up a scope pattern like that! Even though it was done on a lab scope instead of an automotve scope it really helps!!
Thanks, Rich

BTW -- it has nothing to do with gaskets, oil pressure, or where the planets are in the heavens. You don't need to kill a sheep at midnight either.
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post #4 of (permalink) Old 01-03-2005, 07:50 AM
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Re: RRich,LEVE,others... : Dspark Ign Mod Quandary

RRich, I took the liberty to quote your reply at JU. John should be reading and replying to it soon.

My only though on this is the design of the modules would also reflect the power/RPM band of the expected load. That has a lot to do with saturation and on time of the coil/module. The faster the RPM, the less the on-time of the coil to prevent burn out. That would decrease the effective dwell at which the plug could be fired.
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post #5 of (permalink) Old 01-03-2005, 10:03 AM
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Re: RRich,LEVE,others... : Dspark Ign Mod Quandary

The faster the engine goes, the less time the coil has to recharge -- and do a little cooling.

Lets look at some numbers: (I'm using v8 numbers here.)
The time between cylinder firings is:
700 RPM -- 10.71 milliseconds = .01071 seconds - (not very long)
2000 RPM -- 3.75 ms
2600 RPM -- 2.88 ms
3500 RPM -- 2.14 ms
6000 RPM -- 1.25 ms
(I know, those R's seem like strange places to show, but bear with me.)
That's the time between firings, during that time the coil has to recharge enough to fire the next cylinder.

Normal Ford Duraspark or old style points:
Simply a switch to turn the current flow on and off flowing through the resistor and coil.
Dwell degrees on points is always about 2/3 of the total time between firings:
8 cyl gives a total of 45 degrees, dwell = 30
6 cyls give a total of 60 degrees, dwell = 45
4 cyls give a total of 90 degrees, dwell = 60
Those systems, like most systems, are degree based. The angle remains the same, just the time interval gets shorter the faster the engine goes.
Using the 2/3 dwell time (8 cyls), that leaves the avaliable time for the coil to recharge:
At 700 RPM -- 7.14 ms
3500 RPM -- 1.43 ms
3500 is where those ignition systems begin to start rolling off - they are "running out of breath" so to speak.
At 6000 RPM they only have .83 ms available to recharge -- usually the coil output is so low at that speed the engine misfires.

Now for the GM HEI -- or the Ford TFI (all of it, not just the coil) or the Ford Duraspark II -- never used in Jeeps.
Remember I said dwell on GM is variable -- on the scope it's the time between the downward square in the middle and the current limiter "blip." That's the ime the coil actually charges the rest of the time is cooling or just idling current through it (after the CL blip.")

Dwell will read about 8-12 degrees at 700 RPM, or about 1.9 ms.
As you rev the engine, the square pulse appears to move to the left, and the blip moves to the right. That's because the charging time is time based, not degree based. But the scope pattern is degree based, so it appears to move.
At about 1800 RPM the "blip" dissapears orr the right hand edge, but the square keeps moving left. Dwell meter reading will keep increasing till it reads about 30 degrees.
At that point the dwell meter will stop increasing and the square will stop moving.
That's around 2600 RPM. Untill then the GM module was actually shortening the time for the coil to charge, preventing "overcharging," where the coil cannot release it's energy fast enough to get a fast rise time.
From then on as the R's go up, it becomes degree based -- limited by the available time between cylinder firings.
The numbers:
HEI Coil charge time in ms:
700 RPM -- 1.9 ms
2600 RPM -- 1.9 ms (Dwell becomes time based)
6000 RPM -- .83 ms
Somewhere just below 6000 RPM the coil output begins to roll off -- that shows the coil seems to need about 1 millisecond to fully charge, but at .83 ms it's still working. The system rolls off significantly about 8000 RPM. That's why they aren't used in high Revving race engines.

I guess you could say that at lower speeds the system is "loafing" -- is able to fully charge much faster than the time alloted to do so -- but at about 2600 it has to "get to work." Much above 6000 it's getting "in trouble."

So LEVE back to your comment -- yes, the speed does the limiting, just the variable dwell and current limiter gives the HEI a "Head start."

Remember, the significant influences that allow that is the coil is wound differently, has less iron core, and is getting a full 12 volts and a higher amperage (primary resistance is less.)
If the module did not limit the dwell time that coil would fry fast! At above 2600 natural physics does it. At the upper RPM end it's limited by the available time between firings.

That's why Direct Ignition works so nice -- the coil only has to worry about charging fast enough to handle one or two cylinders, not all of them. They can loaf and still perform. They have all the time in the world to recharge -- relatively speaking.
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post #6 of (permalink) Old 01-03-2005, 12:02 PM
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Re: RRich,LEVE,others... : Dspark Ign Mod Quandary

Woah, Hey I finally remembered my login name. You get so used to the computer doing all your thinking that you forget the important stuff.

Anyway I'm the guy that was doing all the testing over on JU.

This page was what whas throwing me:

It shows that if the module is stamped with D8VE-12A199 then they are Dura-Spark II.

Obviously this is wrong I I kinda guessed that after testing all these modules. All stamped D8VE-12A199

One thing I did notice is that it appears the GM HEI unit "learns". Wehen I first started the Jeep on the GM unit it did not have the current limiting "Blip" on the end but grew there the longer the jeep ran. Does the Dura-Spark II also do this??

Running around with my scope was fun. The CVR (Constant Voltage Regulator)? It realy is a pulse generator. The voltage still goes to 14.8 volts but in little spurts

Would that make it a Temperature Controlled Pulse Generator? (TCPG)? Found out you can test it with a test light to see if it's working. http://users.adelphia.net/~john.stre...eQuickTest.htm

Would anyone be interesting in viewing the pictures over here to keep all the data in one place??
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post #7 of (permalink) Old 01-03-2005, 12:14 PM
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Re: RRich,LEVE,others... : Dspark Ign Mod Quandary....


The Duraspark -- he's looking at the older type Duraspark - the original Ford type that Jeep used, not the DuraSpark II that's comparable to the GM HEI. Apples vs. celery.
The Duraspark he has is only an electronic switch, replaces the points, but does not create any higher energy. And I think he has the resistor still installed - can't tell for sure with the pattern.
Dwell will always be about 30 degrees on an 8 cyl, about 45 on a 6 on those. It does NOT have the variable dwell like GM.

[/ QUOTE ]

Curious... I believe his ignition module has a blue strain relief grommet, just like mine, which for lack of a better way to tell, should indicate a Dspark II ignition module.

But I guess it doesn't explain the fixed dwell angle exemplified in the Oscope readings...

He said he does have a resistor installed on Coil + Term RED. Which would be appropriate for Dspark II. Curious how the 1.35 ohm resistor here is designated for solid state ignition and Dspark I is not regulated by a resistor at all:

Also interesting is that it seems that, chronologically, Dspark I <u>followed</u> the Dspark II, with improvements in voltage and broader cap.. Not only that, this page would suggest that Dspark I and III were only used in California ignition setups and Dspark II was the production 48 State application. Prior to model year 77, the ignition system was simply solid state... Is that just totally wrong?

You can find this pesky dspark pdf file here.
post #8 of (permalink) Old 01-03-2005, 02:21 PM
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Re: RRich,LEVE,others... : Dspark Ign Mod Quandary....

That's the trouble -- correct information is almost impossible to find on the DuraSpark II.

I "lived" through the 70's troubleshooting/diagnosing the Fords -- and taught at the Ford training center sometimes.

Ford realized that dwell variation between cylinders was driving emissions higher than they could live with - caused by points - too much dwell variations, which cause timing variation and higher emissions.

They came out with the DuraSpark electronic ignition - seems like it was about '73 but not sure. It was the first version (same as Jeeps used later after they got tired of the Prestolite trash.)
Now the original is referred to as the DuraSpark I - but when there wasn't any other version, the (I) wasn't used. (You don't name your kid John the first. John gets that title AFTER John II or John III exists.)

I've seen the reference to 2 different resistor Ohm values before, but cannot verify it - never noticed. It's possible the Calif version was the lower value - IF there were two types. The lower resistance probably gave the coil a little more "poop" but would increase the current, making it even more unreliable than the higher resistance ones. It would be "pushing it."

Then later on, partly because of California, partly because of the smaller V8's - 302 etc, Ford still had an emissions problem - Ford had to do something quick.

GM had come out with their HEI in '75 - it had a much hotter spark, higher available output - about 40 KV, much longer duration time, about 2.75 ms as opposed to ALL the others of about .75 ms, and a faster rise time. And it was reliable to boot! The weak part was the rotor flashing through to ground. It was a great system!!! (Believe it or not, Pontiac built 500 cars way back in '67 with it - wasn't reliable enough, almost all were recalled. I had one till someone swiped it in one of my classes.)

Ford developed the DuraSpark II (the 2nd generation of Ford electronic ignitions) - it had to get around GM's patents, but the result was nearly identical to the GM. It was used in many California cars and the smaller V8's. It did not use an ignition resistor, had a variable dwell, a current limiter, 40 KV output, higher current, longer duration, and had similar, but different connectors than the (I)-- slightly more squared looking. The II's module looked to be identical to the (I), square aluminum box. You almost have to have them side by side to see the difference in the connectors, but they will not interchange (if they did, it would let the smoke out!)

Both I & II had a few minor problems -- one being intermittant, another being too sensitive -- it would pick up CB signals and radio interference too easy - even from mobile telephones - no cell phones then. Notice on the Dura II cars there's LOTS more ground straps to help kill the RFI - even on the lower control arms and exhaust pipes to ground the static!
And the rise time wasn't quite as fast as the GM. Fast rise time helps blow off deposits on the plugs.

The connector colors originally did signify what module was what, but so many "rebuilders" and "aftermarket" units distorted that. I think originally there was blue - Calif DuraSpark (I) that had a built in retard for starting ease - (Calif timed initial timing different and had a different advance than the 49 states.) It needed that retard to get started without bucking.
Red was the 49 state version of the DuraSpark (I) - same thing only no crank retard.

Then when the DuraSpark II came out it was black as I recall.

Then "aftermarkets" came along -- they used yellow, red, blue, black, green, pink, even clear grommets. No way to tell what you had anymore. Ford started sueing them - nearly an impossible task. Many were coming in from China.

The aftermarket folks switched tactics to dodge the lawsuits. -- they started saying "rebuilt" modules - supposedly the guts were removed, new electronics put in. They used the original aluminum boxes -- mixing up the numbers! It was a fiasco -- still is!

(I bought several (50?) blue connector modules with the California Dura I numbers on them and BLUE grommets from a defunct Ford dealer's stock -- all in Motorcraft boxes. Turns out NONE of them were Calif types with the retard circuit.

You have to go by the connectors - squared = II, rounder - (I).

As far as I know, there never was a DuraSpark III - the generation that followed the DuraSpark II was an entirely different system - TFI - Thick Film Ignition. It too had the same characteristics - output - as the GM HEI. It has a Hall effect pick-up instead of the magnetic pick-up coil. The module is mounted on the side of the distributor itself. It got rid of most of the bugs the Dura I and II had -- and had a faster rise time. (The square coil had much less iron core so the rise time got faster. It really was a great ignition, and reliable. But it still occasionally would trigger to a radio signal - tear open the stock wiring harness next to the distributor and you'll see shielded wires in the harness!
And the TFI had EST -- Electronic Spark advance -- the computer decided what the advance should be. All you could do was set initial - and that was critical to within 2 degrees.

On a scope the pattern on a Dura II, a TFI, and a GM HEI are look the same. You can't tell the difference.

The scope pattern on the DuraSpark (I) or points system look identical to each other. -- As well as most other "electronic ignitions" out there.

As far as the GM "learning" the current limiter -- that's a new one on me -- wonder if you just didn't see it or there was a connection problem - either the scope, scope's ground, or even the power wire to the coil? If there is anything that limits the +12 voltage to the coil (or he module's not grounded good - the screw through it, the current limiter shuts off, no "blip." Otherwise I don't know, I doubt it's that smart!

The EEC systems, I, II, and III were mainly fuel control, but they did have -- Electronic Spark Advance -- EST. (EEC I was a nightmare!!!!!!!!!)

The large cap and rotors on Fords were used on both the DuraSpark II and the TFI systems. The old (I) used the small caps -- as a rule -- but there were exceptions!!!

BUT-- the cap size does not always indicate I or II - I've seen the small cap distributrs used with the II -- stock original!

The data available on websites is all over the place as far as accuracy goes.

One thing that I know for sure -- combining the best of all the ignitions makes a great system for Jeeps.
The big cap and rotor for increased insulation, with the 8MM wires.
The Ford magnetic pick-up coil inside the distributor - for simplicity.
The TFI square coil - for power.
The elimination of the ignition resistor and 10 ga wires to it - to get lots of energy to the coil.
The use of a remote heat sink mounted GM HEI module for the switching of the high power.

And -- something I haven't heard any comments on -- the use of an adjustable vacuum advance diaphram to tailer the timing advance curve to the carburetor.
Most folks when the do the ignition swap have also done a carb swap. The distributor curve has to be set properly to get the best results.

You'd never believe how much of a difference it makes to get everthing working together properly.
It's not difficult or expensive, just takes a little fiddling.
Get the ignition powerful (HEI/Ford hybrid, use the right plugs, not aftermarket trash, get the timing curve correct, and get the jetting correct.
See my previous posts on "propane trick" to get the mixture correct and see my posts on timing advance for the advance curve.

Your 258 will "come alive!!!!"

Sorry for putting everyone to sleep with the world's longest post.
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post #9 of (permalink) Old 01-03-2005, 03:25 PM
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Re: RRich,LEVE,others... : Dspark Ign Mod Quandary....

Not boring to me. Thanks alot RRich it was a great read.

I got what might be an original Jeep Dura-Spark box, one from South Africa and one from who knows were but dosn't match anything else I have.

I'm sticking with my Steath HEI inside an used Dura-Spark box.

I already have the TFI and just need to play around with my timing curve yet. Right now my 79 distributor seams to have a better curve than my 84 distributor but that's just seat of pants test.

Thanks for taking the time to respond.

I got two good shots of the HEI curves. One right after it started and on a min. later, both at idle.

Right after you start the jeep at idle.

Goose the throttle onece and you get this curve:

Now there may be other things like voltage going up after starting. After the alternator has recharged the battery after starting the jeep. Goosing the throttle probably recharged the battery quicker or something while the voltage was still low it didn't need to limit the current to the coil. Just a guess though.
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post #10 of (permalink) Old 01-03-2005, 03:52 PM
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Re: RRich,LEVE,others... : Dspark Ign Mod Quandary....

I just got done cleaning out an old DS box. Stealth! Hehe. Way back when there was a fellow, TeamRush, that told me "the 1979 distributor had a longer slot for the advance(mechanical/vacuum?). I tried to take my stock '79 apart but ended up twisting some of the screw heads off. I'm useing the '85 distributor which I think got most of it's advance from the computer. I'll need to check that out some day. Maybe sombody else can shed some light on this??? Is that the condensor from inside an HEI distributor?
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