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).
Technical analysis of carburettor modifications, including enlarged chokes and restrictors, to improve power output on Phantom and S.S. engines.
| Identifier | ExFiles\Box 13\3\ 03-page115 | |
| Date | 21th October 1929 guessed | |
| -4- old four port Phantom with full silencer system and are consequently lower than we are at present accustomed to on the S.S. engines. With the enlarged choke and restrictor, we found that removal of the inner float chamber walls, to provide free air flow, appreciably increased the power. We do not consider the float chamber walls will offer any obstruction if we only slightly increase the choke diameter and reduce the restrictor so that about 1.850 sq. in. free choke area is permitted when the restrictor is in its fully withdrawn position. With the restrictor in its closed position, an annular choke would result and we think this could be as much as, or more than, 30% of the max. choke area. The carburetter would then perform as a small fixed choke(carb.)/at low speeds, or small throttle opening, and should give all the necessary pick up as we know can be obtained from an undersized fixed carburetter. As the depression increases the carburetter will expand and so provide for good power output. Throttle edge carburation would be used to supply the demands up to the point of pick up from the choke spray holes which, by virtue of the small choke area, would take place at low speeds and load - probably at 30% of the combined speed and load of a normal fixed choke carburetter. We are fitting up the spare expanding carburetter on these lines and when we have satisfied ourselves the power | ||