Confusion about running conventional coils in wasted spark

[Jon k]

Hey guys - I am on a bmw website and one of the guys chimed in about running my stock coils in wasted spark.

"Do you know any one that uses these coils as a waste spark system? waste spark coils are designed totaly different than single DI coils. Manufacturers only use waste spark because it is cheaper to manufactur then hand you a line that it is better since it fires on exhaust stroke. Waste spark plugs are also different in design since the spark jumps the opposite direction and will ruin conventional plugs very rapidly.

The more I think about it, the more I think it is impossible to use your coils as a waste spark. I suspect this is a misunderstanding of the application of waste spark systems."

So uh.. am I ok running my car in WS or not?

[Joethemechanic]

"Do you know any one that uses these coils as a waste spark system? waste spark coils are designed totaly different than single DI coils. Manufacturers only use waste spark because it is cheaper to manufactur then hand you a line that it is better since it fires on exhaust stroke. Waste spark plugs are also different in design since the spark jumps the opposite direction and will ruin conventional plugs very rapidly.

Ok, first off this guy is WRONG on several points.

Waisted spark plugs are no differant than any other plug.
The differace is that the wasted spark coil packs generally have two high voltage terminals, each terminal is connected to either end of the high votage winding inside the coil. One terminal discharges to positive and the other discharges to ground.
so what happens is one plug tends to wear the center electrode more and the other plug tends to wear the ground strap.

I am assuming that you have a coil on plug or DI system, in this case you can fire them either DI or waisted spark, only with 1 coil per plug all of the coils discharge the same, so plug wear will be uniform.

as far as firing the plug on the exaust stroke, all it does is allow manufacuteres to use fewer coil packs drivers and wires.
For 99% of aplications waisted spark is perfecly suitable.
Some more specifics about your car will help to further advise you!

[MegaScott]

Hey guys - I am on a bmw website and one of the guys chimed in about running my stock coils in wasted spark. "Do you know any one that uses these coils as a waste spark system?

If you are talking about using COP coils in a wasted spark configuration, yes there are people running them here in that manner.

waste spark coils are designed totaly different than single DI coils.

True, although "wasted spark" only means that the coils fire two cylinders at once, one on the exhaust, the other on the power stroke.

Factory wasted spark coils use a single coil to spark two plugs, in series with the coil. one plug on the low side of the secondary, the other plug on the high side of the secondary.

Manufacturers only use waste spark because it is cheaper to manufactur

Naturally, also it is easier to implement WS, it is only required to use a crank wheel and a single sensor for wasted spark.

then hand you a line that it is better since it fires on exhaust stroke.

No better no worse as far as compared to COP. The standard street engine does not rev high enough to make any difference as far as this is concerned, however Wasted spark is measurably better than a Distributer and a single coil. With COP you can have individual cylinder spark maps, and that's where the difference is.

Waste spark plugs are also different in design since the spark jumps the opposite direction and will ruin conventional plugs very rapidly.

Sure the spark plugs spark twice as much, but they are no different than your standard "high mileage" spark plugs, such as the iridium or platinum plugs. There was a test of your standard run of the mill 50c spark plugs, and it was found they had the same amount of erosion as a standard ignition configuration.

The more I think about it, the more I think it is impossible to use your coils as a waste spark. I suspect this is a misunderstanding of the application of waste spark systems."
So uh.. am I ok running my car in WS or not?

If this is impossible than how is it that people are doing it now? It makes no difference to the Air fuel mixture if the spark starts at the center electrode, versus the ground electrode, all it cares about is spark quantity and duration.

To configure your COP for wasted spark is to pair up two coils that fire on opposite stroke, and fire the primarys at the same time using one coil driver per coil.

[Jon k]

Thank you for addressing that!

That block quote was from a member of another forum. Do you mind if if I tag your response to his original so he can see the opinion?