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).
Performance data from an ignition test at various engine speeds.
| Identifier | ExFiles\Box 37\1\ scan 256 | |
| Date | 1st April 1924 | |
| R.R. 403A (40 H) (SL 42 12-7-23). J.H.D. EXPERIMENTAL REPORT. Expl. No. REF: HS{Lord Ernest Hives - Chair}/ACL/1.4.24. (5) Both Ignitions. REVS. | LBS. | MAX. | MIN. | MEAN. 2500 | 132 | --- | 42° | 44.5° 2250 | 141 | --- | 40° | 43.5° 2000 | 144 | 46° | 37° | 41.5° 1750 | 151 | 44° | 36.5° | 37.5 1500 | 152 | 44° | 33° | 37.5° 1250 | 151 | 41° | 29° | 35° These curves were taken to shoe advantage of firing a comparatively pure charge, by relieving back pressure and reducing amount of residual gases, - but are practically identical to figures obtained with std. manifold. ACL/GF. | ||