Topic: coil on plug, with a twist.. would it work?

[oddballmotorsports]

so, I need new coils for my build..  since I'm weird,  I have decided to try something.  coil on plug..  now I can already hear y'all saying, but there's 4 cylinders,  and two coils,  well, the answer (I hope) lies in a dodge hemi (5.7) coil.  its a "wasted spark" setup where the coil boot goes to the spark plug, and then a wire runs to the companion plug..  In a dodge its two plugs firing on the same cylinder but the design is the same. and the primary coil is 3 ohms..  so, yeah thats it.  think it will work?

[dusterdude]

Yes

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[drumstyx]

Huh? Why do we need to get so fancy? Over on the Concours forums, people run coilovers by just splitting the coil supply wires and hooking them up to 1-4 and 2-3.

[oddballmotorsports]

that's an option too..  however if one were to run 4 individual coils,  with 2 in parallel in each circuit, they would have to be 6 ohm coils as when you run resistors in parallel, their resistance splits..  I'm sure there's 6 ohm coils out there..  what coil packs are they running?    the reason I thought a waste spark COP would be better as its cheaper than buying 4 coils..   but then one has to find weird spark plug wires as the second coil tower has a funky connector..  allthough it could be easily modified to accept a "regular" wire..

[przjohn]

You don't say what bike you are working on but the SOHC 4s that I have worked on are already wasted spark ignition. There are 2 coils going to 4 plugs, why not just replace the existing coils with like coils if they are bad?

[PlungerWaffle]

Give it a shot! What could possibly go wrong?

[oddballmotorsports]

a shot I took,  and it worked..  Looks a little bulky,  but I think I am going to make some air scoops that cover the coil plate which will also direct air over the motor, or possibly run a different tank thats a little wider..  not sure yet..  the only thing I'm worried about is these coils are designed for 6k rpm at limited bursts.  so 10k is pushing it a ton.. I have a feeling their going to fail quick..  their cheap enough to where I can replace them as needed, but I would rather not.. 

[Duke McDukiedook]

If this is a 750 you will want to put some 1 ohm 10 or 20 watt resistors inline with the positive feed to each coil. 3 ohms allows too much amperage for the ignition switch and kill switch and will eventually fry them.