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).
Tests and modifications related to carburettors, air pipes, and silencers, referencing Morris Motors.
| Identifier | ExFiles\Box 121\3\ scan0098 | |
| Date | 28th November 1940 guessed | |
| THE S.U. CARBURETTER CO LTD ADDERLEY PARK, BIRMINGHAM. 8 - 2 - did not seem to us to offer sufficient benefit to justify complications to the carburetter and ignition system. Figures obtained by Messrs. Morris Motors on their tests on the same engine substantially confirm our results. When an air pipe and silencer are fitted the relationship between pulling and cruising ratios follows no law. We found that satisfactory results could be obtained so long as the total length of pipe on the mouth of the carburetter did not exceed 2"; with longer lengths than this no satisfactory results can be obtained. It seems that if some additional weakening device has to be fitted one must first find some way of cancelling out the results of pulsation. The only thing we have found which has considerable effect on this is a very long passage of small bore between the float chamber and the jet. We tried connections from the air pipe to the top of the carburetter, without obtaining satisfactory results, although Messrs. Morris Motors claim to have done better with this arrangement. We find that a reasonable degree of silence can be obtained without a silencer, by keeping the induction pipe size small; this reduced the peak power slightly but the loss was, in our opinion, well worth while for benefits obtained in other directions. The smaller bore pipe had curved ends and the flow was kept as smooth as possible, we have not derived any benefit from fitting buffer ends or rightangle bends at the ends of the pipe. There are various ways in which additional weakening can be obtained on the S.U. carburetter; probably the simplest is to apply suction from the manifold to the end of the piston spindle, the full pressure must not be applied at this point, otherwise it will keep the piston up all the time when idling. Ctd. | ||