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 issues and modifications for a 25-EX fitted with an A.C. petrol pump.
| Identifier | Morton\M19\ img253 | |
| Date | 3rd October 1931 guessed | |
| COPY. RE - 25-EX FITTED WITH THE A.C. PETROL PUMP. We found that with the petrol pump giving a 5 lbs pressure to the carburetter float chamber, it was necessary to reduce the needle valve seating E.70397 from .156" to .125" to prevent flooding. We did not find during our sustained high speed runs in France that we were short of petrol as has been experienced on other occasions. A peculiar feature of this system, which we did not definitely fathom, was the drying up of the float chamber after standing two or three hours. We made quite sure that it was not caused by leaks and we assumed that the cause was due to the syphoning back of the petrol into the tank. Another feature was misfiring after slow running on the road when accelerating. This was put down to the pump not delivering sufficient petrol at slow speeds i.e. 8 M.P.H. The misfiring was momentary on some occasions but on others it was very pronounced and the car definitely held back for some time before regaining its speed. We overcame the boiling trouble by fitting the supply pipe from the tank along the under side of the top flange of the frame, keeping it entirely away from the engine. Hs{Lord Ernest Hives - Chair}/G.W.Hancock. | ||