ignition secondary voltage? how much is too much?

[fe66comet]

I was checking out some DIS coils today and got to thinking that with the range going from 35000 to 60000 secondary volts, how much is too much? Obviously higher voltage is going to cause faster erosion of the spark plug electrodes but lower voltage will cause un-burnt fuel in a high compression engine. It would seem the 60000 volt coils are designed for use with a supercharger, but would the same idea apply to an engine running a 11:1 or 12:1? I wonder at what point does the spark become hotter than needed and it is just extra wear and tear on ignition components like wires and plugs? I am thinking something middle of the road ( hotter than stock but cooler than all out race) voltage would make sense and could running too hot actually cause detonation from pre ignition? What's your guy's take on it? Thanks....Jon

[Barry_R]

Fantasy numbers is all you are seeing.  Voltage roughly equates to electrical "pressure".  Secondary voltage will be whatever is needed to overcome system resistance (cap, wires, rotor gap) and jump the plug gap under cylinder pressure.  If your application requires 20,000 volts to do that - 20,000 volts is what you're gonna get.  They can say any number they want, but unless your system requirements go up - volts will remain reasonably similar.  A coil with a bigger rating - if true - will provide more "headroom" if you are marginal ie. needing 25,000 and only having 25,000...

Now go looking at other functions are you might have some opportunities there - simplistically used terms like amperage and spark duration come to mind (my electrical/electronic buddy would describe this stuff in much more accurate and mind numbing detail).  That's putting more energy into the spark and having it last longer - both can be good things.  An OEM style inductive system will provide more spark duration than a capacitive discharge system like an MSD.  That's why an MSD requires multiple sparks at low speeds - the spark comes and goes very quickly - an advantage at high RPM becomes a disadvantage at low RPM...

[fe66comet]

I see what you mean about used and maximum voltage, of course amperage goes up as the gap or load would increase. I guess I am over thinking it being an electrician by trade LOL. It is interesting how you pointed out that the stock ignition would have a longer duration than the MSD capacitive discharge unit, I never really thought about it until you mentioned it. I guess I was thinking of the coil more as a capacitor in the way it stores energy until it reaches a set potential then discharges rather than responding to required load to overcome resistance as in a potential resistor does. I guess I would have to determine as you said how much potential resistance I could encounter under load with a healthy spark and good quality parts. The other stated factor in selections were primary resistance, as I thought resistance in the primary side would be a bad thing? Would this not reduce response time at high rpm and create more load on the primary circuit? In the system I am building up duration and spark control will be managed by the PCM, are their ways of improving the spark duration and high speed spark over the original arrangement? I hate to start collecting up parts and find I could have built a better mouse trap, it would seem that the coils, wires and plugs are the only upgrades that you would need in a waste spark system.

[chris401]

Ran Accell Super Coil sense 97. Claims 80,000+ volts. Motorcraft and NGK plugs wear normaly.

[fe66comet]

Wow that's a lot of coil juice, I was thinking of using the Jocobs  or Granatelli Motorsports kit. I will have to check out the set up you have also, thanks.

[chris401]

Got it and a pile of other parts when Super Shops was liquidating.

[fe66comet]

We had a super shop in Chicago Heights IL. , man that seems like a million years ago LOL.