Topic: Hi-po coils burn out warning / potential?

[Garage_guy_chris]

Been looking into hi performance and hi output ignition setups one thing that keeps coming up is a statement that goes something like this:

WARNING!!! Do not operate or apply power to the ignition system with one
or both spark plugs disconnected. Operating or applying power to the coil or
ignition system with one or both spark plugs disconnected will cause IMMEDIATE
FAILURE to the coil. Ignition coils are NOT WARRANTIED for this reason.

This concerns me a bit and seems like it could be a problem. Id like to get a little more information and some insight on this before i pull the trigger on anything. I would much rather buy coils that can deal with a plug disconnected if such a thing exists

-The first thing is why would a coil do this?
-Are OEM coils afflicted with this problem?
-Is this something they "may" happen or is it "will" happen if a plug gets disconnected.
-Can a fouled plug cause the coil to fail?
-Do Dyna Coils suffer this fate? the site / instructions does not say anything about it and I have never heard anyone complain about this
-is there someway of knowing what Im looking at or is it only internal differences?

[dave500]

what unit is that for?most transistor ignitions will kill the box with no plug in place,or a bad resistor cap.

[Bodi]

The Kettering system coil produces high voltage in its secondary coil when power is disconnected. Energy stored in the internal magnetic field from the primary coil has to go somewhere. With plug cables connected it makes the sparks. The rated maximum secondary coil voltage is tens of thousands of volts, in practice the real voltage is whatever voltage the plugs spark at.
Powering and disconnecting a coil with no plugs is not advised because the energy can't just stay in the coil waiting for a plug. It must be dissipated immediately. The secondary coil voltage is theoretically unlimited. It finds a way to discharge, either through the very high resistance of dirt on the outside of the coil or the internal coil insulation as heat - or by arcing internally. Arcing internally will cause carbon tracking through the insulation along the arc path. That is catastrophic damage.
Stock coils are susceptible to this damage, high performance coils more so because they can have a higher voltage capability and their insulation may be better. It's best not to ever fire a coil with no plug(s) connected (and grounded). Usually it doesn't ruin the coil but sometimes it does.

[dave500]

well put bodi,the stock coils with points will endure this no end,like a fouled plug etc,but you can get unlucky,its like bottle necking a high pressure,itll blow back down the line.