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 comparing engine horsepower (HP) against revolutions per minute (R.P.M.) under two different test conditions.
| Identifier | ExFiles\Box 19\4\ Scan310 | |
| Date | 4th May 1931 guessed | |
| H.P. R.P.M. BLACK = UNIT TEST ON HEENAN & FROUDE WATER BRAKE, WITH STANDARD SILENCER WITHOUT CUT-OUT. RED = DYNAMOMETER TEST AT ROAD WHEELS WITH STANDARD EQUIPMENT AS ABOVE | ||