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).
Analyzing the results of various carburetter arrangements on Phantom II and 25 HP engines.
| Identifier | ExFiles\Box 181\M13\M13.2\ img067 | |
| Date | 7th July 1931 | |
| ORIGINAL To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}11/AD/7.7.31. +7080. x8080 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 ramming 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. | ||