With this article....

Michael E. Gemmel wrote: “Each cylinder has an ignition coil pack over one spark plug, and a regular plug wire connected to the other spark plug. Further, the coil pack also has a plug wire attached to it that extends to the opposite cylinder bank. It appears that each cylinder shares a coil pack with another cylinder. Each of the two plugs on a given cylinder is fired by a separate coil. One plug has a coil directly attached, and the other is fired via an ignition wire connected to a coil located on another cylinder on the opposite bank. The benefits would be one-half the number of coils (8 vs. 16) compared to each plug having its own coil, and of course less weight.”

“Cryptojoe” wrote: “Being the good Motech Graduate I am, I can say that the extra plug fires during the power stroke in order to more full burn the hydrocarbons. While this does add to NOx (oxides of nitrogen) and ozone emissions, it relieves the catalytic converter from becoming overwhelmed with unburned hydrocarbons. Unlike the Japanese systems of the late 1970s and early 1980s, which avoided the use of catalytic converters, the second ignition allows additional power in the down stroke while lowering the need of restrictive catalyst plates in the converter. This increases breathing, and in turn adds to horsepower output as well.

“As you may recall, in the 1980s Japanese manufacturers skirted trade restrictions concerning EPA standards for unburned hydrocarbons by place spark plugs either in the exhaust pipe (which fired with every piston ignition) or in the exhaust manifold (which fired each time their corresponding cylinder fired). Chrysler morphed this idea to include dual fired plugs on each cylinder, which allows the firing to take place closer to top dead center, and then again when the piston is on the back side of the power stroke.”



It appears the second spark is on the down stroke...

With shorty wires, both plugs fire on the compression stroke...

So, I have a question, and that is...

Do you get more power with both plugs firing on the compression stroke, or with one firing on compression, and one firing in overlap???

This question has been racking my brain for some time, and I believe the mopar crate hemi has the shorty style wires...is this correct???

If you have any input on this, or just wanna laugh at me, for asking what may be a silly question please post up...

Any input will be greatly appreciated...

P.S. Sorry for the long thread, and triple periods...

 

wooo...nobody knows....spooky

 

I don't think that you would want 2 flame fronts colliding with each other. But then again, who knows. I know it isn't me.

 

There seems to be a lot of mis-information out there when it comes to the Hemi spark plug issue and the firing sequence. Let's look at the knowns. There are two plugs per cylinder. Each cylinder has only one coil. Each coil has a plug wire extending across the engine to a plug on the opposite bank.

Each cylinder has a paired cylinder on the opposite bank. I know that cylinder 1 is paired with cylinder 6. When coil #1 fires on the compression stroke, coil #6 also fires at teh same time, on that cylinder's exhaust stroke. So the two plugs on cylinder 1 are energized, one from coil #1 direct, and one from the wire leading from coil #6. Likewise, the two plugs on cylinder 6 fire at the same time, one from coil #6 direct, and one from the wire leading from coil #1.

So if you install shorty wires and remove the long wires, there will be not much affect, since both paired coils fire regardless. The only difference is both plugs on each cylinder will get their power directly from the coil at that cylinder. Also, the coils will continue to fire in pairs, so at any given time, there are four spark plugs firing; two on the compression stroke and two, at the paired cylinder, on the exhaust stroke. Ccompression and exhaust strokes are both at the peak of the upstroke.

 

I would also think, that firing a plug in the exhaust stroke has zero chance of igniting any unburnt fuel. The ratio of unburnt fuel to available oxygen has got to be below the ignition threshold. That's why we have catalytic converters instead of just a spark plug in the exhaust pipes.

Roger...

 

...i run shorty's... i love em...plus my engine bay looks soo much cleaner without the squid on top...