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 graph showing the increase in Brake Horse Power and Brake Mean Effective Pressure for a 20 HP engine after various modifications.
| Identifier | ExFiles\Box 102\5\ scan0009 | |
| Date | 6th October 1928 guessed | |
| 20 H.P. POWER OUTPUT WITH THE FOLLOWING MODIFICATION TO STD. ENGINE. DEPRESSION AT 2750 R.P.M. REDUCED FROM 2.5" TO .7" HG. BY TWO ZENITH TRIPLE DIFFUSER CARBURETTERS. COMPRESSION RATIO 5.45 TO 1 LARGER VALVES 1.400" DIA: PREVIOUS 1.200" DIA: INLET CAM DURATION INCREASED BY 28° ON C'SHAFT EXHAUST CAM DURATION INCREASED BY 12° ON C'SHAFT EXHAUST CAM LEADS INLET CAM BY 120° CURVES WITH FREE EXHAUST AREA PAST FULLY LIFTED VALVE 1.2 DIA: = 1.04 □" AREA PAST FULLY LIFTED VALVE 1.4 DIA: = 1.44 □" % GAIN IN MAX: B.H.P. OVER 'S' A.{Mr Adams} 22.4% B. 29.6% C. 57.5% D.{John DeLooze - Company Secretary} 71% AXES LABELS: BRAKE HORSE POWER. ENGINE R.P.M. BRAKE MEAN EFFECTIVE PRESSURE LBS / □" CURVE LABELS: S: B.H.P. STANDARD 20 H.P. & B.M.E.P. STANDARD 20 H.P. A: AS 'S' WITH 5.45 C/R ZENITHS B: AS 'A' WITH 1.4 DIA VALVES C: AS B, NEW CAMSHAFT D: STRONGER VALVE SPRINGS, B.M.E.P. D CURVE CAMSHAFT DIAGRAMS: NEW CAMSHAFT: IO TDC, IC 66°, EO 64°, EC 8° OLD CAMSHAFT: IO 12°, IC 44°, EO 48°, EC TDC | ||