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Gen 3 Hemi ignition coils

General engine tech -- Drag Racing to Circle Track

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Circlotron
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Gen 3 Hemi ignition coils

Post by Circlotron »

Just wondering about the coils for Gen 3 Hemis. Seeing they connect to two spark plugs, are they internally two individual coils or one double-ended coil like on a wasted spark setup?
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Re: Gen 3 Hemi ignition coils

Post by Walter R. Malik »

Circlotron wrote: Thu Jan 07, 2021 8:18 am Just wondering about the coils for Gen 3 Hemis. Seeing they connect to two spark plugs, are they internally two individual coils or one double-ended coil like on a wasted spark setup?
One coil, two ends ... positive and negative.
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Re: Gen 3 Hemi ignition coils

Post by miniv8 »

I'm not sure how they are built, but I'm following this as I am hungry for Gen III Hemi info.

I have read where they had issues with spark blowout under boost, they kept closing the gap as boost was increased, until they installed the stock Chrysler coils. Then the gap could be opened up again. Not sure what brand the aftermarket where initially, but the story is good eh?
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Re: Gen 3 Hemi ignition coils

Post by jalai »

Walter R. Malik wrote: Thu Jan 07, 2021 9:46 am
Circlotron wrote: Thu Jan 07, 2021 8:18 am Just wondering about the coils for Gen 3 Hemis. Seeing they connect to two spark plugs, are they internally two individual coils or one double-ended coil like on a wasted spark setup?
One coil, two ends ... positive and negative.
No. One primary and two secondary (weird idea #-o ).
These curves are measured with plug wires (secondaries) connected together.
Image
Circlotron
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Re: Gen 3 Hemi ignition coils

Post by Circlotron »

jalai wrote: Fri Jan 08, 2021 4:54 am
Walter R. Malik wrote: Thu Jan 07, 2021 9:46 am
Circlotron wrote: Thu Jan 07, 2021 8:18 am Just wondering about the coils for Gen 3 Hemis. Seeing they connect to two spark plugs, are they internally two individual coils or one double-ended coil like on a wasted spark setup?
One coil, two ends ... positive and negative.
No. One primary and two secondary (weird idea #-o ).
These curves are measured with plug wires (secondaries) connected together.
Image
int(ch1*ch4)
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Re: Gen 3 Hemi ignition coils

Post by Krooser »

The guys I have talked to run stock coils. No advantage to those high dollar ones in the real world.

The second plug fires 5 degrees atdc to clean emissions so a smaller cat can be used. But we cant run a Hemi on dirt around here cause the Brand X guys think you are running two 100 amp magnetos....
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Re: Gen 3 Hemi ignition coils

Post by Walter R. Malik »

jalai wrote: Fri Jan 08, 2021 4:54 am
One primary and two secondary (weird idea #-o ).
These curves are measured with plug wires (secondaries) connected together.
Image
There are a lot of motorcycle coils built similar to that.
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Re: Gen 3 Hemi ignition coils

Post by Walter R. Malik »

From what I have recently been told ...
Earlier Gen III coils and later Gen III coils are very different.
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Re: Gen 3 Hemi ignition coils

Post by PRH »

I haven’t looked at the plug wiring on a G3 in ages, but my recollection is that the early ones had the coil sitting on the cylinder that’s firing, and the other lead was going to the cylinder that’s on the overlap.

So, the two plugs for each cylinder are fired 360* of crank degrees apart, and from different coils.
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Re: Gen 3 Hemi ignition coils

Post by jalai »

Walter R. Malik wrote: Fri Jan 08, 2021 11:10 am There are a lot of motorcycle coils built similar to that.
Can You tell some example (I can try to find it and test)?
I'm almost sure, that there are'n any motorcycle coil like this (one primary winding / two secondary windings).

Early model with wire to other cylinder are probably at waste spark, but it is other story.


My poor English may be messing things up :roll: ...
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Re: Gen 3 Hemi ignition coils

Post by miniv8 »

"Similar" might be the word making all the difference.

Do the newer Hemi coils fire each plug in relation to crank degrees regardless of RPM or do they just fire the second plug in series with a fixed dwell delay?

Can this second firing be controlled or altered in any way?
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Circlotron
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Re: Gen 3 Hemi ignition coils

Post by Circlotron »

Krooser wrote: Fri Jan 08, 2021 10:06 am The guys I have talked to run stock coils. No advantage to those high dollar ones in the real world.

The second plug fires 5 degrees atdc to clean emissions so a smaller cat can be used. But we cant run a Hemi on dirt around here cause the Brand X guys think you are running two 100 amp magnetos....
If the second plug fires some degrees after the first plug then as well as two secondaries the coil assembly must have two independent primaries as well. In other words two completely separate coils. If there is one primary and two secondaries then both plugs will fire at the same time. You couldn’t have a single coil secondary feeding both plugs strapped together - the first plug to fire would suddenly pull the voltage down and stop the voltage rising high enough to make the other one fire. It’s not impossible, but I’m doubting the plugs are connected to each end of a double ended coil like in a waste spark setup because on the hemi both plugs fire on the compression stroke and so both need full voltage. That’s a total of double normal voltage, unlike a waste spark setup where the plug that fires on the exhaust stroke needs (and wastes) relatively little voltage.
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Re: Gen 3 Hemi ignition coils

Post by Walter R. Malik »

Circlotron wrote: Fri Jan 08, 2021 7:57 pm a waste spark setup where the plug that fires on the exhaust stroke needs (and wastes) relatively little voltage.
That is exactly what the original Gen III hemi coils were meant to do.
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Re: Gen 3 Hemi ignition coils

Post by JohnP »

Several years ago, I looked into the ignition used on the Chrysler Crossfire. From what I could tell, one plug fires before the other one, but they alternate. One time it's the leading plug, the next time it's the trailing plug. I don't know on what other vehicles it was used.
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Re: Gen 3 Hemi ignition coils

Post by jalai »

Chrysler Crossfire coil is probably same as used at some Mercedes Benz engines.
Bosch 0 221 503 035
It is a real dual coil (two separate similar coils).
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