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).
Engine performance, focusing on carburettor configurations, M.E.P., and experiments with different setups.
Identifier | Morton\M13.2\ img068 | |
Date | 7th July 1931 | |
-2- Hs{Lord Ernest Hives - Chair}/Fml/AD7.7.31. contd. Superficially one would say that we shall then get better low speed M.E.P. than with the carbs. close to the engine and nearly the same top H.P. Summarising the results, it would seem that there is no way of getting ramming over the whole speed range. You can have the maximum at any spot you like, the lower the speed the greater the maximum ramming that can be obtained. The greater the maximum ramming, the more M.E.P. will be lost at the extremes of the speed range away from the peak. We are inclined to think that the P.2. valving reduces the single carb. advantage at high speeds. We still feel that the ideal for our class of car is to have the peak M.E.P. about 45 M.P.H. It is difficult to see much advantage in the Bentley arrangement with its complication of petrol feed, float chambers duplicated etc. One would imagine that a single S.U. would have been better for their class of work. We quite see your point about the difficulty of very slow speed pick up on 6 cyls. with a fixed throat carb, though we had not appreciated that we had done many tests to confirm it experimentally. We are making some tests with a Zenith to prove the point, however. We did try a single Zenith two years ago but are not positive if it would snap open up below 10 M.P.H. It was the triple diffuser of the type you have. We observe what a good silencer you can get on LeC.2924 and appreciate the difficulty of getting a twin carb. in with the steering column where it is. We hope, if the Zenith works, to be able to use one of the LeC.2924 carbs. on a sports China. In doing these various experiments on China and Japan we have been wondering what advantage the turbulent head gives us on the 25 HP. It reduces audible detonation but this is not our limiting factor on the 25 HP. but general roughness which the turbulent head seems to accentuate. If we had no audible detonation on the standard car it is doubtful if we should go above 5.25 C/R with the 110° shaft (compare 16-GIV and Trials car on last Brooklands meet for smoothness). It certainly | ||