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).
Negative effects of the vacuum feed system on engine performance and fuel consumption.
| Identifier | ExFiles\Box 56\1\ Scan001 | |
| Date | 24th July 1925 | |
| X5510 To Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. to CJ. BJ. c. to EP.{G. Eric Platford - Chief Quality Engineer} Hm.{Capt. W. Hallam - Head Repairs} c. to CWB. R7/M24.7.25. RE. VACUUM FEED. X.3579 X.5510 It has been pointed out that the vacuum feed both on the 20 HP. Silver Ghost and New PhantomCodename for PHANTOM I, does affect the light load slow running of the engine. With this we agree. This vacuum feed suction may also have increased the smell of the exhaust (unburnt petrol), and also the banging in the exhaust. It would be worth while to carefully measure the petrol consumption with and without the autovac. It is possible that when the petrol gets hot, as it is sure to do under the bonnet, the effect on the slow running is still worse, and it may make a material increase in the consumption. This could easily be investigated. There seems little doubt about all this. What about an alternative? Long ago we thought of a vacuum pump but it is doubtful if that would be a cure for some of the faults, and we should then have pump and vacuum complications. We do not want to go back to a sealed back tank, perforation of which stops the car. R.{Sir Henry Royce} | ||