Herb Kephart wrote:Month old subject here...
Month old? Actually several years old.
What I used to hear, back when dragster people and the like were the only ones looking for that last little bit that they could get out of an engine, was that the center electrode of the plug, being red hot, it was easier for electrons to flow if the center electrode was positive, and the colder plug shell was negative. Had to do mostly due to the red hot condition (think of an old glass radio tube) than anything,
It was a baseless assumption. Electron flow in a vacuum tube is due to thermionic emission. Thermionic emission occurs at relatively low temperatures and voltages, and is a phenomenon of black body radiation.
Electron flow across spark plug electrodes is caused by high voltage breakdown of the air charge in the cylinder. The result is an arc of extremely high temperature. The high voltage used in internal combustion ignition systems is necessary due to the cylinder pressure at the end of compression, which causes the breakdown voltage to be substantially elevated over what it would be at normal atmospheric pressure.