spark polarity

[blue77bay]

Hypothetically, if i was running a twin plug set up and instead of having to mount 8 ls2 coils around the engine what would be the problem with using an EDIS coil pack on each side of the engine? ,1 coil would drive both plugs on each cyl but they would be opposite polarity,can this be a problem? i realize it would require sequential timing but it might be easier to do that than hang coils everywhere ,the only disadvantage i can really see is loosing the ability to individually trim spark timing WRT each other ,on the other hand is this feature really a big plus or just something to play with ?

[Piledriver]

If you are going to the expense of twin plugging the heads, another ~$75 for a second set of LS2 coils at least allows you to do it properly, and keeps the ignition noise as far away from the ECU as possible.

The coils can be mounted almost anywhere, they have plug wires.

I would not bother with dual plug heads if I couldn't tweak the leading/trailing timing as required.

[miniman82]

Hypothetically, if i was running a twin plug set up and instead of having to mount 8 ls2 coils around the engine what would be the problem with using an EDIS coil pack on each side of the engine? ,1 coil would drive both plugs on each cyl

You're not thinking about it correctly, both plugs would fire at the same time. If you want to control leading/trailing spark per cylinder, you would still need to have one EDIS coil fire on the power stroke of cyl 'A' and the exhaust stroke of cyl 'B' depending on firing order. A simpler way to visualize that is it's the same thing as a single EDIS system, just doubled up on the other set of plugs. That would then lead to a mess of wires all over hte place, and wouldn't look very neat. I'm with pile, get the CNP's.

[Munchhausen]

once i had an idea about twin plug set up. Maybe here are guys could give a statement if its a bad or good idea

Using a magnetic-pickup triggered CDI-box from a bike for each cylinder. They normaly trigger allready at small singnals like 1V
I am shure it can be triggert by some windings around the existing sparkwire.
Here a shoddy drawing of what i mean:

twin plug.JPG

Would more a nice solution for dissy/carb engines which want to go twin plug, than ECU-engines. But its a kind of simple.
My problem is that the only CDI-boxes i know are from smaller 2stroke engine and need a high voltage supply.
But I am shure there are 12V ones. Maybe somebody know a 12V version from motor bike or aftermarket one.

munch

[blue77bay]

Hypothetically, if i was running a twin plug set up and instead of having to mount 8 ls2 coils around the engine what would be the problem with using an EDIS coil pack on each side of the engine? ,1 coil would drive both plugs on each cyl

You're not thinking about it correctly, both plugs would fire at the same time. If you want to control leading/trailing spark per cylinder, you would still need to have one EDIS coil fire on the power stroke of cyl 'A' and the exhaust stroke of cyl 'B' depending on firing order. A simpler way to visualize that is it's the same thing as a single EDIS system, just doubled up on the other set of plugs. That would then lead to a mess of wires all over hte place, and wouldn't look very neat. I'm with pile, get the CNP's.

yep i'm on the right page now mini,i was just thinking i could fire both plugs in 1 cyl by triggering just 1 coil of the coil pack,i was just looking at the possibility instead of having to dangle 8 ls2 coils all over the engine ,its bad enough having to mount 4,and i rekon pile is right ,leading /trailing adjustment may be more beneficial than i am currently realizing, i have not played with twin plug set-ups before

[miniman82]

Twin plugs as I understand them only pay dividends when you can either increase flame speed across the chamber in large bore engine (both plugs at the same time), or when you can have leading/trailing control to guarantee a complete burn every time. Alfa Romeo engines were famous for this, with their line of 4-cylinder hemi-chambered dual plug engines.

[Piledriver]

Even on the big bore dual plug it is likely to require some stagger.

The hemi practically requires it due to a lousy chamber shape from a combustion standpoint.

The latest Chrysler "hemis" have large squish pads and dual plugs.. not really a "hemi" at all, in the classic sense.
Much better.

[Dale M.]

Some late model FORD PU (Ranger) with 4 cylinder has a dual plug system and by what mechanic at shop (where I looked at it) says the dual plug system was just that. A complete double up of all components firing on same engine cycle.... His comments were its a "bitch" to work on because of plug placement.... But electrically its just a duplicate system ....

Dale

[miniman82]

Amen to that! My wife used to have a Ranger with that 8-plug motor, trying to do a tuneup was like brain surgery. Passenger's side is a snap, since there's nothing in the way. On the driver's side plugs you need 2 long extensions, 2 universal joints, a plug socket with the rubber thing so the plug don't slide out, and someone to spot you as you attempt to locate the plug since you can't see nothing. Or, pull the intake manifold.

Ford's lucky it's a pretty bulletproof motor, though I've heard the head cracks very easy if you overheat it. Same issue as the Pinto iron head ones, then you need a new head or one of those Esslinger aluminum ones. $$$$.

[Redline Weber]

This is for "blue77bay" an answer to your question, which none of the "moderators" could provide.

First, I worked on the design of the first "twin tower" coil, a coil for the Buick GN is 1983.

You are correct in that this coil has a +/- secondary current flow direction.
THUS only a sparkplug with a large center electrode should be fitted...

The kit would be TWO (two coil) EDIS units (as stated) using TWO crankshaft sensors NEXT TO each other around the Target Wheel to provide for Spark Instant offset.

One EDIS would be "top" plugs, the other "bottom plugs"
One twin post coil would require plug wires fitted to the cylinder heads on opposite sides of the engine.

UNDERSTAND the each coil would fire INTO a cylinder at compression, another at overlap.

The above stated method is used by most OEM's with twin post coils.

One exception is the newer Hemi 6.1 that uses both versions of coil secondary leed placement.

Lance

[Piledriver]

?
We usually try not to answer questions already answered a month ago.

Citroen 2CV (started production 1948, but the design was mostly prewar) was waste spark, I strongly suspect waste sparks actual first use was ~contemporary with spark ignition itself, as making a double ended secondary on the HV transformer costs about the same and you need half as many, saves money, and it skips the need for a distributor.

It had a coil with 2 HV plug towers... one on each end. In 1948.

DIS still rocks though, and it is well supported by MS1 & MS2 if someone wanted to use a pre-existing ignition system.

Once past a certain energy level, the spark polarity probably doesn't matter too much.