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Old 08/07/07, 05:15 PM   #1
malcolmzilla
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Calgary, AB, Canada
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Hot coil and Duraspark unit

How hot should a coil and Duraspark unit get? Warm to touch, or hotter?

I swapped out my factory coil for a MSD one that is supposed to take 12V constant, and pulled the resistor (cleaner wiring).

We noticed the coil gettin hot when trying to crank and the engine didnt start, found a grounded tach lead, got that sorted and it fired up. I also noticed the Duraspark unit was gettin warm too. Thinking the short mighta been pullin on 'em constantly and was the cause?

I have yet to check it after a quick idling session tho. I can put the resistor back in but would prefer not to. The Duraspark sees 12v constant regardless.

TIA

Malcolm(zilla!)

68 Bronco, 08 Megacab, 46 Willys, Bronco "buggy"

09 WR450, 10 EXC530 Christini AWD, 11 Berg 570
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Old 08/07/07, 05:55 PM   #2
Broncobowsher
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Most (if not all) the durasparks should be running a ballast resister.
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Old 08/07/07, 10:47 PM   #3
malcolmzilla
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Idled it a bit, coil still gets way hot... I'll put the resistor back in and see what happens to the MSD, supposed to be good for 12V constant...

Why would the duraspark get hotter w/o the resistor? It's powered by 12V off the ignition terminal on the start solenoid in stock form, and thats how my Painless does it...

Thanks.

Malcolm(zilla!)

68 Bronco, 08 Megacab, 46 Willys, Bronco "buggy"

09 WR450, 10 EXC530 Christini AWD, 11 Berg 570
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Old 08/07/07, 11:26 PM   #4
broncnaz
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Put the resistor back in. There are few coils that are good for 12V constant and most of those are race only which normally only run for a few minutes at a time. I have a feeling that the MSD info is misleading in where they say that a balast resister is only needed in a points type system. Most stock electronic setups will already have the required resister and I have a feeling the the MSD ignition boxes also have a resister in them. Might want to call MSD and clarify.
The Stock coil only gets 12V constant during starting once you let off the key it recieves less than 12V. Even the older points type setups had the resistor in them as the coil just cant take the full 12V for long the oil gets hot and will crack the coil.

73 Ranger 2 1/2 lift 302 TFS heads NP435,PS,PDB, tierod over, 33x10.50x15 BFG M/T
71 Sport 63,000 miles all orginal except for cut fenders 302 3sp 4.11's D44/BBTrac lok rear
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Old 08/08/07, 12:03 AM   #5
Broncobowsher
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If you are running an MSD ignition box, that is a different storry. The capacter discharge ignition boxes run a different technology then the standard eletronic or points distributer.

With a Capactor discharge box (MSD 6A and the like) the coil get a hit of about 600V. It acts like a transformer and just delivers the energy out as a high voltage spark.

The conventional coil (Duraspark, points) uses a completely different technology to deliver the spark. The coil get power, develops a magnetic field. When the power is release (points open) the field collapses. As the field collapses into the core it collapses very hard and suddenly. Much faster then the charge built up. This sudden collapse slams through the windings and spits out a spark.

The ballast resistor is there to keep the points from burning on a points sytem as the contacts will arc if the voltage is excessive (above 8~9V). But eletronic ignition (duraspark) still needs it to limit the energy going into the coil. If the energy is not restricted properly more energy will go into the coil then comes out the spark plug wire. That energy has to go somewhere and that somewhere is in the form of heat.

When Ford came out with the newer style TFI ignition, they did away with the ballast resistor. But they have a trick in doing so. since they are pushing a full 12V into the coil, they give it a very short dwell, just a degree or three at idle. That is enough time to charge the magnetic field but not enough time to pump excess energy into the coil that it can't do anything with other then form heat with it. So that is the special case of the non-ballast resistor eletronic ignition. Of course there is a computer to control the timing.
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Old 08/08/07, 12:54 AM   #6
nvrstuk
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Tfi

So you're saying the TFI coil shouldn't be used with the Duraspark box because of the difference in dwell angle? Interesting. I'd like to hear more.

I've fried 3 TFI coils (non-Motorcraft) in a week. My Motorcraft last 3,000+miles.

I am currently doing some radiator mods and have been running hot at idle till I work it out. My Duraspark and coil TFI, got moved to the grill support above the left headlt. Very, very hot there. After frying $$$ I wired in the stock round can Duraspark coil and put in on the inside drivers coil (front just above the body mount). 100+miles today, no issue. Course I didn't sit and let it idle either.

I'd like to know where the info is on the dwell difference on the TFI coild. I know several guys running it w/o an issue...guess I"m NOT one of them anymore! lol


Oh, my Duraspark box"es" (including spares) runs at 146F and the iron core on the TFI coil is pumping out 236F while running! OUCH

Thanks

Strrroker powered... 418 cubes in a roller block, 518 HP... Trick Flow, Mahle, etc... this brings a whole new meaning to the term "burping the throttle". Still 24+ forward gears...
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Old 08/08/07, 01:32 AM   #7
malcolmzilla
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Wow, some way smarter folks on here than me! I did catch some of that tho...

OK, I'll put the ballast resistor back in, the MSD instructions do say to use the resistor with "points or stock ignitions", I guess Duraspark is "stock"... I do have a new NAPA Duraspark unit to put in, along with a new distributor and leads...

http://performanceparts.com/images/p...es/msd8222.jpg

I still say the resistor is ugly. Are there different types? My Painless kit comes with a "dodge" type according to the parts guys.

http://www.mopartruckparts.com/image...or-5206436.jpg

Is there a smaller one I can bury in the loom, or do they all generate too much heat? Where is a good spot to drop it out? where was it stock?

Right now its dropped out on the firewall above the transmission but right behind the carb, thats a bad spot if you blow fuel out apparently? I'm thinking passenger fender over by the start solenoid and 50 amp Painless fuse is good?

Thanks again.

Last edited by malcolmzilla; 08/08/07 at 01:45 AM..

Malcolm(zilla!)

68 Bronco, 08 Megacab, 46 Willys, Bronco "buggy"

09 WR450, 10 EXC530 Christini AWD, 11 Berg 570
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Old 08/08/07, 02:03 AM   #8
broncnaz
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Stock was built into the wiring itself from the ignition switch. Might be a smaller one availible but I'm not sure the pass side would probably be a good choice.

73 Ranger 2 1/2 lift 302 TFS heads NP435,PS,PDB, tierod over, 33x10.50x15 BFG M/T
71 Sport 63,000 miles all orginal except for cut fenders 302 3sp 4.11's D44/BBTrac lok rear
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Old 08/08/07, 08:49 AM   #9
nvrstuk
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Ballast resistors are all ugly. They generate a lot of heat. You can hide it but not by anything that has a melting point below 400F.

Find a stock resistor wire as a guide for length and use it. Don't tape it up into a wire loom/harness tho.

Strrroker powered... 418 cubes in a roller block, 518 HP... Trick Flow, Mahle, etc... this brings a whole new meaning to the term "burping the throttle". Still 24+ forward gears...
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Old 08/08/07, 02:12 PM   #10
Broncobowsher
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Quote:
Originally Posted by nvrstuk View Post
So you're saying the TFI coil shouldn't be used with the Duraspark box because of the difference in dwell angle? Interesting. I'd like to hear more.
I never said that...

I just mentioned how the power was put into the coil, nothing about the coil itself.
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Old 08/08/07, 02:39 PM   #11
76Broncofromhell
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I run no ballast wire on my coil with a stock Duraspark II. I did a lot of reading about it and there was no consensus that with a coil rated for a consistant 12 volts, running it with 12v would affect a Duraspark module.


I've been running it for over 2.5 years with an MSD blaster 2 coil and 12 volts with absolutely no problems.

The Duraspark will get warm maybe even too warm to touch when running for a long time. If you took one apart you would notice that well over 70 % of its size is heat sink. The actual chip is small. On my Flat Fender I used a GM HEI module hooked to an Aluminum heat sink running 12 volts, and that sucker gets hot!

'70 Bronco - 408W
'45 Ford GPW - 351W
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Old 08/08/07, 02:50 PM   #12
nvrstuk
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20 gears forward...no reverse!

WA
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To clarify??

Your post

..."When Ford came out with the newer style TFI ignition, they did away with the ballast resistor. But they have a trick in doing so. since they are pushing a full 12V into the coil, they give it a very short dwell, just a degree or three at idle. That is enough time to charge the magnetic field but not enough time to pump excess energy into the coil that it can't do anything with other then form heat with it..."

Since I'm literally burning up coils, my "logical" deduction was that since there's
" not enough time to pump excess energy into the coil that it can't do anything with other then form heat with it..." that since I'm burning up coils that would be a logical conclusion since "heat" and "burning" are usually associated so closely and I"m using a TFI coil w/o the rest of the TFI ignition.

So to clarify, there isn't any association between dwell angle and burning up TFI coils with a Duraspark then? Just trying to find the association if any.



I've rewired, already eliminated the TFI coil and haven't melted anything yet. I did relocate the coil to a more convenient mounting location tho.

Strrroker powered... 418 cubes in a roller block, 518 HP... Trick Flow, Mahle, etc... this brings a whole new meaning to the term "burping the throttle". Still 24+ forward gears...
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