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).
Carburettor testing and adjustments concerning petrol level, diffuser, and slow running slot.
| Identifier | ExFiles\Box 42\3\ Scan027 | |
| Date | 11th November 1926 guessed | |
| contd :- -3- PETROL LEVEL. It was found absolutely necessary to keep static petrol level as high as possible and we have now raised it to the top of the diffuser tube or about a tenth of an inch below the point of flooding. We know this is not a safe level but below it the trouble becomes much more pronounced. DIFFUSER. Numerous tests were made with holes of various size and in different positions in the diffuser tube. The best arrangement seemed to be with six .062 dia. holes at a distance of .400 from the top of the tube and the same number and size at the bottom of the tube. Very little difference with regard to acceleration could be detected with any of the arrangements tested. The fall in the level of the petrol round the outside of the diffuser tube below the level in the float chamber was proved to be due to the demand of the idle running jet tube which draws from this well. This was tested by taking the idling supply from an external source when the level did not sink below the float chamber level and in consequence the sprayer started to deliver at approx. 200 r.p.m. lower speed. This results in a slight improvement to the acceleration but is not a solution to the trouble. SLOW RUNNING SLOT. We realised that increasing the length of the slow running slot at the edge of the throttle would enable us to obtain a rich mixture at the 'change over' point and also control contd :- | ||