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 showing ignition advance versus RPM at the point of audible detonation for standard and long duration cams under full load.
| Identifier | WestWitteringFiles\Q\2-July1927-September1927\ 40 | |
| Date | 16th August 1927 guessed | |
| IGNITION ADVANCE WHICH JUST CAUSES AUDIBLE DETONATION AT A CONSTANT SPEED, FULL LOAD. IGNITION ADVANCE. 10 20 30 40 50 60 R.P.M. 500 600 700 800 900 1000. LONG DURATION CAMS STD. | ||