[Speedy Squirrel]

Turbo’s have no appreciable piston dome (lower cr), so twin plug is not as effective/required. Twin plug requires/demands less ignition timing. Some people interpret this as less chance for knock. This is not true. Combustion is faster, and produces higher cylinder pressure. It makes slightly more power (around 5%) for this very reason. Faster combustion has less time for heat transfer (loss) to combustion chamber. Big dome pistons benefit considerably more, 10% or more, because of the flame propagation issue being lessened.

CDI multi spark is kind of like mopping up. CDI spark duration is notoriously short. More sparks give CDI more chances to ignite the mixture, in case it missed it the first time. Once the O2 near the plug is consumed though, that’s all she wrote.