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 various carburetter arrangements for a car engine.
| Identifier | ExFiles\Box 181\M9\ img025 | |
| Date | 11th July 1931 | |
| To R.{Sir Henry Royce} From Ha/Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to Da.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} ORIGINAL 87080 x5080. We have been conducting various experiments on the positioning of carburetters with a view to determining the best all round arrangement for a car engine. At the same time we have been investigating the characteristics of various carburetters, as you suggested, but our tests are incomplete because we so far have not had the same type of carburetter in every position - (1) Single carburetter feeding six cylinders. (2) Single carburetter feeding three "ramming". (3) Carburetter feeding three cylinders as close to the cylinder block as possible. (4) Two carburetters simultaneously feeding six cylinders. The results we have so far obtained, however, indicate the following :- Arrangement (1) - is best for maximum power. Arrangement (2) - is best for low speed M.E.P. but is slightly down in power at top speed. Arrangement (3) - is a compromise between (1) and (2) and does not seem to have the merit of giving exceptional high speed power as we had hoped. We have tried this both on the 40/50 and the 25 HP. and Sheet 1 attached shows the results on the 25 HP. It will be noted that the depression on the Zeniths was slightly lower than the Claudels. We think that these curves may be unduly unfavourable to the carburetters placed close to the cylinders because the Zenith carburetter does not give such good distribution as the Claudel, but combined with the results obtained on the 40/50 this curve indicates that we should certainly expect no marked increase in H.P. from this arrangement over the single or R.R. double arrangement of carburetters. On the whole we cannot say that the distribution of the two carburetters placed close to the cylinders is poor but it appears to be slightly more sensitive to the pulverisation of the petrol stream than when arranged as on Sheet 1 Fig.1. One reason may be that it is not so easy to arrange an effective hot spot when the carburetters are placed thus. | ||