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 comparison between a Napier Car and a 40/50 model.
| Identifier | ExFiles\Box 81\1\ scan0050 | |
| Date | 20th May 1912 guessed | |
| Particulars of performance of Napier Car. Petrol consumption 23.9 m.p.g. 53.2 ton m.p.g. Speed on track 77.1 m.p.h. Windage 10.3. sq.ft. Weight without passengers } 4,369 lbs. Total weight with passengers } 4,990 lbs. Gear ratio 3 to 1. Particulars of performance of 40/50 Rolls-Royce Car. Petrol consumption 24.32 m.p.g. 57.07 ton m.p.g. Speed on track 78.26 m.p.h. Windage 13.01 sq.ft Weight without passengers } Total weight with passengers } 5,257 lbs. Gear ratio 2.9 to 1. | ||