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).
Comparison of particulars from two R.A.C. tests between a Napier and another 6-cylinder vehicle.
| Identifier | ExFiles\Box 81\1\ scan0047 | |
| Date | 1st June 1920 guessed | |
| [Handwritten top right]: Speed & Ref Trial [Handwritten left margin]: X789 Particulars of two R.A.C. Tests. | | 6-cylinder Napier | 6-cylinder Rolls-Royce | Remarks. | |---|---|---|---| | Route taken | London to Lands End to John O' Groats to Edinburgh and back. | London to Edinburgh and back | - | | Petrol consumption | 23.9. m.p.g. 53.2 ton m.p.g. | 24.32 m.p.g. 57.07 ton m.p.g. | The ton mileage of the Rolls-Royce is 7.25 better than the Napier. | | Speed on Brooklands. | 77.1 m.p.h. | 78.26 m.p.h. | - | | Windage | 10.3 sq.feet. | 13.01 sq. feet. | The windage of the Rolls-Royce was 26.3% greater than that of the Napier. | | Total weight with passengers. | 4990 lbs. | 5257 lbs. | The Rolls-Royce carried 5.35% more weight than did the Napier. | | Gear Ratio | 3 to 1 | 2.9 to 1 | The gear ratio of the Napier was 3.5% lower than that of the Rolls-Royce. | | Bore and stroke of engine | 5 x 5 inches | 4½ x 4¾ inches | - | | R.A.C. Rating | 59.9. h.p. | 48.6. h.p. | The R.A.C Rating of the Napier is 23.25% greater than that of the Rolls-Royce. | | Date of trial | June 3rd. to 18th.1912. | Sept.6th to 13th.1911. | - | | ||