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).
The petrol level performance of a P.2 twin choke carburetter, comparing present and modified designs.
| Identifier | ExFiles\Box 13\3\ 03-page310 | |
| Date | 21th April 1931 | |
| R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} c. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. Hs.{Lord Ernest Hives - Chair} Bv. X7080 E1/M21.4.31 P.2. TWIN CHOKE CARBURETTERS. X.7080 Referring to Hs{Lord Ernest Hives - Chair}/Lov{Mr Lovesey}3/KT17.4.31, the slope obtained on the petrol level when turning under normal conditions is surprising. On the design as made the main spray jets are in the ideal position in the centres of the float chambers and are therefore unaffected by angular changes of level of the fuel. As however all the features of the carburetter cannot occupy the central position there are certain of them that will flood or become cut off beyond a certain angle. We have made an investigation to see what improvement can be obtained in the design within the limitations imposed by the engine. We are anxious at the same time not to increase the distance between the choke tube and throttle valve. The following table gives all the figures for the carburetter at present being tested and also the improved figures we expect to get by modifying the design. | | Present angle. | Expected improvement by modified design. | | :--- | :--- | :--- | | Petrol floods out of top of accelerator pump. | + 26° | + 40° | | Accelerator pump begins to cut out | - 6° | - 30° | | Limit of correct balance of float immersion. | + 10° | O.K. for any angle. | | Starvation - supply hole to main jet variable restriction begins to uncover. | - 25° | Minus 40° | | Main jet variable restriction begins to flood at top. | + 30° | + 40° | | Petrol floods out of top of low speed jet housing. | + 28° | + 40° | | Petrol floods out of low speed air supply hole. | + 37° | + 55° | | ||