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).
Definition and settings for the 20 HP battery ignition timing.
| Identifier | ExFiles\Box 37\1\ scan 246 | |
| Date | 23th October 1923 | |
| x3949 To EY. } " EP.{G. Eric Platford - Chief Quality Engineer} } from EFC. " Ey/Shn.} EFC5/T23.10.23. X.928 - IGNITION TIMING. X.3949. It would appear that some want of definition exists in the setting of the 20 H.P. battery ignition. It will be agreed that (1) The hand advance allows for 20° on the distributor, or 40° on the engine. (2) The automatic advance allows for 15° on the distributor, 30° on the engine. This is a total of 70° on the engine. Sometime back we believe the total advance was only 54°, viz. from 10° a.d.p. to 44° b.d.p., and that 10° of the total increase of 16° was given to the hand advance, for the purpose of improving starting by retarding the ignition lever. One would have supposed that this additional 10° was added on the retard, but as a result of enquiries we are given to understand that the Test Dept. are only giving 5° a.d.p. on full retard on production, which means that the [strikethrough]maximum[/strikethrough] now full advance point would be 65° b.d.p. instead of only 44° as previously. With the range of the battery ignition set thus early, starting by retarding the ignition lever will be rendered more unlikely and particularly so if the make ratio of the contact breaker exceeds .5, as is likely. From the above it will be seen that it appears to us that the battery ignition range is being set | ||