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).
Investigations into vacuum feed issues affecting petrol economy on 40/50 and 20HP models.
| Identifier | WestWitteringFiles\N\2July1925-September1925\ Scan37 | |
| Date | 1st August 1925 | |
| R.R. 235A (160 T) (S.H. 159, 11-3-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2800 TO HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} Copy to C.I. EW. [Text struck through] VACUUM FEED ON 40/50 AND 20HP. R2/M10. 8. 25. x8510 [Text struck through] x5570 [Text struck through] I am anxiously awaiting the result of the investigations regarding vacuum feed to the 40/50. You will remember that some time ago I suggested that it was possible that the heat to the vacuum feed chamber and to the float carburetter was excessive, or one or both of these parts may have some serious effect on the running of the engine, and the petrol economy. Regarding the last named we find that it is difficult to get more than 12½ m.p.g. from the EAC. which is here, and also to get more than 20 m.p.g. from the G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 111. which is here. Regarding the G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 111., on this particular engine the distribution when cold seems very bad, and after running a short time throttled a large amount of petrol accumulates somewhere in the upper end of the high speed throat. This runs down after the engine stops and dribbles out of the petrol drainage pipe. I personally am a little suspicious that we are not metering the petrol on either of the present cars as accurately as we did on the old 40/50. If this is not the case then something else is happening, such as the extra high temperature mentioned above, or the fact that the overhead valves require considerably richer mixture when running light at slow speed. [Handwritten Signature] R.{Sir Henry Royce} [Stamp: RECEIVED 13 JUNE 1925] | ||