[Tyson Schmidt]

Steve W. The Bosch plugs with the multiple electrodes do not shroud the mixture at all. The ground electrodes aim at the sides of the center electrode, leaving the tip wide open and facing the oncoming piston.

Porsche uses 3 ground electrodes as standard equipment on the newer cars. (FR5DTC) I'm pretty sure they know what they are doing.

The Splitfires are a joke.

MSD works because the air/fuel ratio that is directly surrounding the plug can change through the 20 deg. of crank rotation that MSD sparks through. (Low RPM) This is due to the turbulence of the entering and exiting gases. (swirl effect) A richer mixture is easier to ignite.

This is how Honda's CVCC head design works. They have a pre-chamber which houses the plug, and feed it a ratio of around 8/1. This ensures easy ignition. The main combustion chamber is fed a mixture of around 24/1. This alone would be difficult-to-impossible to ignite, however, the pre-chamber is already lit so it all gets burned. The resulting average of the two mixtures equals a lean-burn engine which is very efficient.