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).
Carburettor tests comparing fixed size chokes with constant depression carburetters and discussing fuel atomisation and power output.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan134 | |
| Date | 25th April 1928 guessed | |
| contd :- -2- The above tests were made with fixed size chokes, the depression consequently increasing with the speed at full throttle. The choke depression at max. power was 4.4 ins. mercury which depression it would be inadvisable to exceed in a constant depression carburetter if we aim at getting max. power output. The above suction appeared to give very good atomisation of the fuel issuing from the Claudel diffuser and even at a speed of 750 r.p.m. full load where the suction was reduced to .43 ins. mercury, it was sufficiently vigorous to maintain good atomisation and excellent distribution. Although these tests have been made with fixed choke and throttle areas with the depressions needed for maximum power output with a constant depression carburetter. Of course if we work at a constant choke depress-ion which we select to give us the greatest maximum power output for our given size ports and induction system - say 4.4 ins. as shewn by experiment - we shall naturally be a little lower in power at the lower speeds than with a fixed choke carburetter. We however think it preferable to sacrifice a little in this direction in order to ensure vigorous and more certain carburetter action at low speeds than is generally obtained with fixed choke carburetters. The vertical straight through carburetter appeared particularly suited for use with the overhead feed weir induction pipe but we must bear in mind a Claudel type diffuser was used which provided a well atomised mixture and so considerably helped distribution. Altogether we found the distribution with this contd )- | ||