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).
Technical comparison of Claudel and Zenith carburetter systems and arrangements.
| Identifier | ExFiles\Box 181\M9\ img026 | |
| Date | 11th July 1931 | |
| -2- Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}6/MJ.11.7.31.Cont'd.{John DeLooze - Company Secretary} Arrangement (4) - Does not seem to have any particular merit as it eliminates ramming completely and whilst producing no more top HP gives a very poor low speed M.E.P. We shall confirm this as perhaps in the case shewn on Sheet 2 the carburetters were altogether too big for the engine when used in this manner. Sheet 2 shews a series of tests on similar lines taken on the 40/50. In each case a camshaft was used giving maximum power in order to shew up clearly any small differences in the various systems. We may expect therefore that the difference will be slightly reduced when a camshaft suitable for the road is used. EMULSION CARBURETTERS - CLAUDEL. Of the carburetters that we have been using, we find that the fixed choke emulsion jet type of carburetter is quite good for distribution, possibly the best of those we have been running. In a condition suitable for road running however, it is not the lowest depression carburetter because as has always been appreciated, if too large chokes are used there is a flat spot at the change over from the slow runner to the diffuser. For any given depression, the emulsion type of carburetter seems to give the best power, presumably because the diffuser pulverises the mixture well and so aids distribution. This carburetter also seems excellent for snap opening up on the road when fitted as a twin, under modern traffic conditions, perhaps the most important feature on any car. We believe we shall have difficulty in getting anything better than the present R.R. twin choke for general, as opposed to sports car, practice. The silencing problem we are at present working on. We learn that Hispanos do not silence by drawing their air through the crankcase but by using a separate casting on the crankcase as a silencer. At the moment we believe we shall be able to get silence at the expense of 1" additional depression at 3000 R.P.M. with a maximum power camshaft. ZENITH CARBURETTERS. With the exception of the horizontal triple diffuser Zenith, such as the one you have at W.W., we do not like this make of carburetter because in most cases it is very susceptible to the throttle position and when a sensitive position is encountered distribution is likely to be very bad. The horizontal triple diffuser Zenith seems to be an exception to the general rule and gave good results when we ran it on the road on a China unit. We are going to carry out some further tests to see whether it will give a low speed pick up below 10 m.p.h. when coupled to 6 cyls. | ||