From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Ignition coil performance, voltage output, and spark plug gap settings for battery ignition engines.
| Identifier | ExFiles\Box 37\1\ scan 189 | |
| Date | 5th December 1930 guessed | |
| WE63 (5) Contd should be the normal plug setting for our engines on battery ignition but with this plug gap the conditions would be so severe such that in certain circumstances our ignition coil would not be able to deliver sufficient voltage to ignite the mixture and there would not be the voltage margin we consider essential to cope with other untoward circumstances such as leakage in the H.T. circuit and the distr. rotor and points burning away. The maximum regular sparking voltage generated on our coil at 12 volts is 10,500, but after the coil has been warmed up by running it in an oven temperature of 80°C on a voltage of 17.5 for two hours this voltage is reduced to about 9000 so that missing on the "pick up" would occur. Presumably the ignition would fail altogether with .030" plug gaps on the pick up with the coil hot, but these conditions are ameliorated by | ||