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).
Fuel consumption tests for the Wraith model, detailing performance issues and comparisons with the 30 HP model.
| Identifier | ExFiles\Box 147\5\ scan0151 | |
| Date | 31th May 1938 | |
| TO Rm.{William Robotham - Chief Engineer} Rm{William Robotham - Chief Engineer}/GR.{George Ratcliffe}8/JH.31.5.38. WRAITH FUEL CONSUMPTION TESTS. Tests were carried out on 24.G.VI. with Delco coil and ignition tower 656 RA.No.16. Standard conditions with ignition set at T.D.C. the part throttle metering was satisfactory, but immediately the vacuum control advance operated bad misfires occured between 15 and 20 m.p.h. Running light with car stationary misfires were bad between 750 and 1500 R.P.M. Several changes were made without appreciable difference these included new R.R. coil and sparking plugs carburation strengthened and weakened. The total advance over the governor was approx. 10 degrees. This was used with advantage on the 30 H.P. 22.G.V. Throttle openings as measured both ways for constant speeds on the level are as follows - 18° at 50 M.P.H. 12.25° at 40 M.P.H. 8.9° at 30 M.P.H. and 5.5° at 20 M.P.H. Total weight of 24.G.VI 1-19-2-21. Axle ratio 9 x 41 and tyres 6.50" x 17". The graph attached shows constant speed consumptions and figures for an average of 42 M.P.H. part throttle tests under the appended conditions. It will be seen from the graph that the standard Wraith is better than the 30 H.P. for part throttle economy to the extent of 1 M.P.G. average. With the vacuum control advance in operation on the 30 HP. it gives an average increase of 1.5 m.p.g. at part throttle up to 50 M.P.H. but when applied to the Wraith the increase is .75 m.p.g. at 50 M.P.H. only. | ||