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, petrol economy, and fuel distribution issues on the 40/50 and 20 HP models.
| Identifier | ExFiles\Box 68\2\ scan0054 | |
| Date | 10th August 1925 | |
| To Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. to CJ. PN.{Mr Northey} 9510 R2/M10.8.25 VACUUM FEED ON 40/50 AND 20 HP. X. 8510 X. 5510 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 chamber 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 12 1/2 m.p.g. from the EAU. which is here, and also to get more than 20 mpg. from the G.111 which is here. Regarding the G.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 HP. 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. R.{Sir Henry Royce} | ||