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 showing a graph of engine thermal efficiency versus load, with an analysis for a Phantom car.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan161 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -6- Expl. No. REF:Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}1/LG211125 GRAPH 1. [GRAPH] Y-axis: PERCENTAGE THERMAL EFFICIENCY X-axis: PERCENTAGE FULL LOAD OF ENGINE Handwritten note: Typical curve for efficient 4 stroke petrol engine. On the Phantom, 9.5 HP is required to propel the car on the level at 30 m.p.h. The engine is capable of develop-ing 60 HP. at this speed. It is therefore only working at 16% full load. Under these conditions every B.HP. developed takes as much petrol as 2 1/2 HP. generated under full load conditions. Owing to these facts every car has a speed, usually about 15 m.p.h. at which it will give the greatest m.p.g. contd :- | ||