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).
Analysis of different carburetter arrangements for the Phantom II and 25 HP models.
| Identifier | Morton\M13.2\ img067 | |
| Date | 7th July 1931 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} ORIGINAL Hs{Lord Ernest Hives - Chair}/Rml/AD7.7.31. +7080. X5080 CARBURETTER ARRANGEMENTS. P.II. AND 25 HP. Further to our 'phone conversation, herewith a curve shewing some results. We used the 114° R.{Sir Henry Royce} shaft as it happened, to be available and this should shew the general tendency of various carburetter arrangements. We agree that with a general alteration in valve areas the results might be different i.e. we can only talk about the existing P.II unit with a long duration, high lift shaft. Analysing the results :- (1) Two S.Us close to Inlet Ports separate 3 cyls. Ramming reduced slightly over R.R. twin carb., peak of ramming raised slightly, maximum H.P. slightly lower than with a single carb., slightly higher than with the R.R. twin carbs. (2) Two S.Us close to engine feeding into common manifold. Effect of a single carb. but poor low speed M.E.P., possibly this arrangement completely destroys all low speed ramming, certainly the carburation is very unstable and slow running erratic. Two carbs..like this are obviously too big for the engine. (3) R.R. Twin Choke. Maximum ramming at 1600 R.P.M. Down in H.P. at high speeds. (4) Single Claudel Carb. Maximum running at high speeds, down in M.E.P. at low speeds but not very much on the two S.Us fitted close to the engine. We think that the arrangement of carbs. as on the R.R. twin carb. is somewhat penalised in these curves because of the higher manifold depression under which they are working i.e. probably 3" instead of 2" of Hg. We are arranging the two S.Us with similar pipes to our twin choke pipes to get an exact comparison of positions. | ||