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).
Test report comparing a new light aluminium air valve against the standard brass valve for a 20 HP carburettor.
| Identifier | WestWitteringFiles\O\2January1926-March1926\ Scan177 | |
| Date | 17th March 1926 guessed | |
| 20 HP. CARBURETTER WITH ALUMINIUM AIR VALVE. The new light aluminium air valve was tested in a standard 20 HP. carburetter unit where it was proved to possess the definite advantage of commencing to lift at a lower depression, and consequently a lower speed than the standard brass valve. The new valve lifted at a depression, measured in the mixing chamber, of 1.2 ins. of water and represented an average light running speed of approximately 390 r.p.m. whereas the standard brass air valve started to lift at a depression of 2.7 ins. of water, or a speed of 540 r.p.m. The earlier lift naturally extends the automatic range of the carburetter and results in a lower light load speed being obtained before it is necessary to resort to the use of the mixture control. The metering characteristics proved to be similar to the standard instrument and curves are here given shewing the variation of the mixture control from its normal position in order to obtain the best possible running. For all carburetter tests we employ the above method as a convenient way of demonstrating any deviation from proportionality. From this curve it is seen that the general characteristic is for the mixture to fall off weak after the air valve starts to rise until such time as the high speed jet comes into operation and again returns the mixture strength to normal. The extent of the weakening is certainly not very great. contd :- | ||