The forthcoming info is from the Bosch Automotive Handbook 9th Edition, 1500+ pages.
Note: this is not the same Bosch Handbook I provided earlier in this thread, this is a later edition but the message on plug gaps is the same.....
'The electrode gap should be, on the one hand as large as possible so that the ign spark activates a largge volume content & thus results in reliable ign of the A/F mixture by developing a stable flame core.. On the other hand, the ign voltage to produce a spark is decreased with a smaller electrode gap. If the gap is too small, however, only a small flame core will be created around the electrode......As electrode gaps increase [ eg due to electrode wear ], the conditions for ignition are improved, but the ign voltage requirement rises.
