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).
Page discussing engine torque curves and acceleration performance.
| Identifier | ExFiles\Box 39\2\ Scan209 | |
| Date | 12th October 1925 | |
| R.R. 499A (50 H) (D.D. 31. 12-6-25) J.H.D. EXPERIMENTAL REPORT. -4- Expl. No. REF Hs{Lord Ernest Hives - Chair}/R m2/LG121025 automatically to 12 ft/sec², or 20%. Naturally, therefore a car noted for its top gear slow running, is necessarily handicapped on low gear acceleration. Torque curve. Every engine has a characteristic torque curve. Another name for a torque curve is the mean push on the piston due to gas pressure at different engine speeds. The speed at which this push is the greatest is the best accelerating speed. Thus in the two curves illustrated, 'A' is something similar to the Phantom engine. It will be seen that its best speed for accelerating on top gear is 13 m.p.h. If a low gear is used, therefore, the low part of the curve A.{Mr Adams} will soon be reached and consequently the indirect gear acceleration of the car will not be good. Curve 'B' which is rather like the Hispano, shews a car whose best acceleration on top gear is 28 m.p.h. It will be obvious that on this type of car the indirect gears will have to be used if the best performance is to be obtained. It will be noted that the 'B' curve gains at high speeds what it loses at low speeds. It is impossible to have both, the design of the car engine is a compromise according to whether a town carriage or sports car is required. contd :- Graph Text: Y-axis: M.E.P. OR PUSH ON PISTON LBS/SQ" X-axis: ROAD SPEED M.P.H. Curve A annotation: 13 M.P.H. BEST TOP GEAR ACCN Curve B annotation: 28 M.P.H. BEST TOP GEAR ACCN | ||