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 plotting ignition firing position against engine RPM to determine the optimal advance for maximum torque and to avoid detonation.
| Identifier | ExFiles\Box 65\4\ scan0319 | |
| Date | 18th August 1925 | |
| 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. FIRING POSITION DEGREES OF CRANKSHAFT. 40° 30° 20° 10° TOP CENTRE 0° -10 R.P.M. 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 3 | ||