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).
Method for developing an adjustable carburetter by measuring air valve lift and depressions to determine the required port area for dilution.
| Identifier | WestWitteringFiles\O\2January1926-March1926\ Scan179 | |
| Date | 17th March 1926 guessed | |
| contd :- -3- It was thought that by slight alteration to the shape of the ports - both those operated by the diaphragm and the air valve - a mixture more nearly proportional would be obtained and it was further decided that attempting to accomplish this by trial and error, was unsatisfactory. We therefore developed the following method - briefly outlined below - whereby it should be possible, having fixed the size of the chokes and the air valve spring to be used, to proportion the air ports to obtain the mixture quality required for the smooth running demands of the engine over its whole range. Method. An 'adjustable' carburetter is used in which the air valve is raised or lowered by means of an adjusting screw which at the same time measures the lift of the valve from its closed position. The ports - both those operated by the diaphragm and those in the dash pot - are made rectangular so that for a given air valve lift the exposed, or effective diluting area, can be easily determined. A 'U' tube is connected with the mixing chamber to enable readings of the depressions to be obtained. The low speed jet is set at the depression corresponding to that at which the air valve would start to lift in a normal carburetter - having previously determined this - and the valve lift adjusted for each throttle smoothly. the air valve lift and the depression is noted. Similar procedure is adopted for the high speed jet except that this is set at full throttle. From these figures we obtain a curve connecting depressions and the necessary port area required for dilution. contd :- | ||