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).
Table showing the timing in degrees for both magneto and battery governed ignitions at various engine speeds.
| Identifier | ExFiles\Box 37\1\ scan 224 | |
| Date | 2nd March 1921 | |
| X.3949. 2.3.21. Hs.{Lord Ernest Hives - Chair} RE GOVERNED IGNITION. The table below gives in degrees the timing position of both magneto and battery ignitions where H.P. commences to drop at various speeds. All readings B.T.D.C. | R.P.M. | BATTERY. | | MAGNETO. | | |---|---|---|---|---| | | Retard. | Advance. | Retard. | Advance. | | 500 | 9° | 21° | 9° | 21° | | 1000 | 19° | 35° | 19° | 30° | | 1500 | 25° | 42° | 24° | 39° | | 2000 | 31° | 46° | 29° | 44° | | 2500 | 33° | 66° | 31° | 65° | Both ignitions taken firing over Inlet Valve, 40/50 test car engine. TCMW. | ||