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).
Experiments on a 20 HP engine to determine if power output can be increased by using a larger carburetter and induction passage.
| Identifier | ExFiles\Box 5\4\ 04-page151 | |
| Date | 17th February 1926 | |
| 20 HP. ENGINE - POWER WITH LARGER CARBURETTER THROTTLE AND 1.5" DIAMETER PASSAGE IN CYL. BLOCK. The following experiments were carried out, as requested, to determine if the power output of the 20 HP. engine could be increased by employing a larger carburetter throttle in conjunction with a larger induction passage through the cyl.block. The throttle of the standard carburetter has a diameter of 1.312" and an induction passage - measured at its minimum dia. - of 1.312" also. The induction passage is not a parallel tube but more of the venturi form, the reason being to allow more metal between the cyl. bores and the induction passage and thereby simplify the casting. Operating with a 1.500" bore pipe, the thickness of the metal between the cyl. bores and the induction passage is only .075 on each side when the passage is perfectly central. The throttle of the experimental carburetter was increased to 1.500" dia. and used in conjunction with a parallel induction passage of the same diameter. In order to minimise the risk of various factors influencing the power comparisons, we made a tube which when fitted in the large induction passage gave the same diameter and contour as possessed the standard engine. We were thus able to make the change from experimental to standard by only removing the carburetter. Of course, the large throttle and standard carburetter bodies were used with the experimental and standard pipes respectively, but the same air contd :- | ||