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).
Testing a large throat carburetter, focusing on low-speed performance and power output.
| Identifier | ExFiles\Box 74\4\ scan0199 | |
| Date | 15th January 1925 | |
| contd :- -3- employed for each test. With regard to the metering of the large throat carb., it was found to be bad at low depressions and possessing a very weak region just before the high speed jet came into operation. It will be remembered that similar trouble was experienced with the early EAC. carburetter when the large throat was employed. Of course, to take full advantage of a large throat at the higher depressions, a lower rated spring would be necessary but our troubles at low depressions would be aggravated. These points were discussed in our report on "Carburetter for EAC Engine" ref. Hg/ACL/LG15.1.25., and should also hold good for the 20 HP. carburetter. MAXIMUM POWER OBTAINED WITH 20 HP. CARBURRETTER. With the large throttle carburetter we went to the extent of completely removing the dashpot unit when the engine was running at full load and strengthening up the mixture. The induction passage was also of large diameter. Under these conditions at a speed of 2750 R.p.m. we were able to obtain an increase of power over standard of only 6%, or actually 2.9 HP. Of course, it was possible and quite probable, that the distribution was not so good under these extreme conditions - although at this speed we had no marked indication of this - and again, owing to the low depression in the throats we were unable to richen up sufficiently to cause a fall off in power, consequently it was difficult to know if the mixture was sufficiently rich to give max. torque. contd :- | ||