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).
Tests and results obtained from an experimental Phantom carburetter compared to a standard model.
| Identifier | WestWitteringFiles\Q\2-July1927-September1927\ 116 | |
| Date | 19th September 1927 guessed | |
| contd :- -2- of the tests and results obtained :- An experimental Phantom carb. was made which had 1.250" dia. high speed choke .850 dia. low speed choke and the air valve ports were enlarged in the same proportion. A low rated spring was fitted which permitted the air valve to be fully lifted at 2500 r.p.m. These modifications represented an increase of inlet area of 126%. Curves shewing the power output and depressions of the large and std. carburetters are appended. At a speed of 2250 r.p.m. the large carburetter gave only 2% more power than the std. model and lowered the depression from 3.2" to 2.5" of mercury. It will be noticed the power readings agree very closely with the absolute induction pipe pressures which is a check that the results are not influenced by such factors as altered distribution. A further test was made in which the air valve and dashpot were completely removed when the engine was running and the jets richened up accordingly. This gave only 4.3 HP. or 4% more than the standard complete carburetter and reduced the depression from 3.2 to 2.1 ins. of mercury. As a check on the power results we see that the ratio of the absolute induction pipe pressures is (29.9 - 2.1) / (29.9 - 3.2) = 1.04 in power and agrees with the actual amount observed. As an additional check we repeated the above experiment of removing the air valve from the 20 HP. and obtained a similar result. Before drawing any conclusions from these tests we made another experiment both on the Phantom and Goshawk to determine how much the depression contd :- | ||