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 pump performance testing, comparing the effects of pipe placement on maximum speed and potential for vapour lock.
| Identifier | ExFiles\Box 92\3\ scan0266 | |
| Date | 31th May 1937 guessed | |
| The pipe was inside the frame and temp. taken behind X member. Frame AIR U.B. Inside out. Tank. Max. M.P.H. Pipe All double single pumps. (III gear.III gear) 17 43 32 28 17°C. 78 76 18 50 42 30 28° IIIrd { III 78 78 60 top 18 50 46 31 32 gear. { III 70 70 55 18 50 44 32 36 { III 65 65 40 21 53 43 34 38 { III 52 III 52 The pipe to the pump was outside the frame. Frame AIR U.B. Inside out. Tank. Max. M.P.H. Pipe All Double Single Pumps. 17 50 42 33 26 Max. Max. 70 17 52 46 34 36 " " 64 16 53 46 33 44 " " 56 In this case the tank temperatures were high owing to a X wing from the N.S. of the car, inspite of the lower air temperature, but there is a noticeable gain in the maximum M.P.H. using a single pump with the pipe outside the frame. When ever the maximum speed was reduced either using the double or all three pumps made no improvement. With the present arrangement of pumps on the dash we are open to vapour trouble but it is difficult to predict with certainty how serious this may become as it is dependent on several factors. (1) Type of fuel used. (2) Tank temperature reached in ordinary running. (3) The under bonnet temperature. Appart from whether this will be serious complaint is not the pumps in this position have to pump all the vapour formed in the system and with high temperature and only moderate engine demand they are working to nearly maximum capacity with the attendant wear on points and diaphragms and noise. | ||