[karl]

Originally Posted by CJMR2T

The main problem with COP's is they over heat and lose charge ability due to this when used in long time duration like road racing.

it's not so much even that, it's that there isn't enough space in the plug well for a coil of significant inductance. that means to get similar energy, you need to ramp up the coil current, which is where the heat comes from.

there's also no cooling for the coils when they're down in the plug well. the COP units that you can see being used are the type with the coil at the top of the coil stick, outside the plug well.

the other type of COP you'll see used in racing is powered by a CDI, rather than charging the coils inductively. they store the energy in a capacitor, instead of in the magnetic field of the coil.

Originally Posted by mr2_mk1.5

from all that I've read, I don't see how that actually is, on wasted spark you still have to jump the plug on the cylinder thats on the exhaust stroke adding more resistance and wasted energy,

it doesn't really waste energy. the main issue is the ionization voltage of the spark gap. that voltage increases with cylinder pressure, and the breakdown voltage in the cylinder on the exhaust stroke is almost nothing in comparison to the cylinder on the compression stroke. once that breaks down, energy essentially avalanches through the ion pocket with relatively low resistance. there isn't much energy lost in the 'wasted spark' at all. it's less than jumping the gap in a distributor even, since the spark gap is smaller.

But lets take one quick look at things here, GM was really the main pioneer of wasted spark and the main purpose of it was to add more stability to the ignition system, for example running 8 cylinders on one coil and a distributor was murder on the coil and wasn't very reliable at high rpms so they brought out the wasted spark system which replaced one coil/distributor with 4 coils and a crank/cam sensor,

kind of. it's not that it was murder on the coil, it's that the coil ran out of time to charge at higher RPM on a V8. with more coils, you can overlap the charge times (look into the motorola 3334 smart dwell chip) and you get double the charge time. that, coupled with improvements in coil drivers and low resistance coils allows for plenty of charge time and full charge at almost any RPM, even in a V8.

the reason i can see for indy cars still using wasted spark is because they don't use extremely high boost, alchol fuel and its cheaper

the indycar engines that ran these coils were pushrod engines and were allowed significantly more boost than the OHC engines. they ran them because they worked, and worked well.

coil on plug works fine in high boost applications when used with a CDI. if you're running an inductive setup, wasted spark is the way to go.