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).
Graph of ignition advance curves against RPM for a single cylinder engine with a 5.2:1 compression ratio, showing conditions for max torque and no detonation.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan295 | |
| Date | 18th August 1925 | |
| 3 BOTH IGNITIONS IN OPERATION. SINGLE CYL. 5.2 TO 1 COMP. RATIO. ADVANCE REQ. FOR MAX TORQUE ALSO ADV REQ. FOR NO DETONATION. THE LETTERS ON CURVES INDICATE THE IGNS. TO WHICH THEY REFER. A B FIRING POSITION DEGREES OF CRANKSHAFT 40° 30° 20° 10° TOP CENTRE 0° -10 R.{Sir Henry Royce} P. M.{Mr Moon / Mr Moore} 250 500 750 1000 1250 BEST COMBINATION FOR MAX TORQUE & MIN DETONATION COMBINATION FOR NO DETONATION. MAX TORQUE CANNOT BE OBTAINED WITHOUT DETONATION A.C.L. 18/8/25 | ||