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 adjustments for improved acceleration in car and aeroplane engines.
| Identifier | ExFiles\Box 42\3\ Scan067 | |
| Date | 31th December 1926 guessed | |
| contd :- -2- the spray holes we have found is much too low to give vigorous and certain acceleration from low idling speeds. With this level and choke dia, we can safely say it is not passable although it is an improvement on the previous horizontal carburetters which with this level would not 'open up' at all. Raising the level considerably improves matters and it has always been our experience, both on cars and these engines, that vigorous acceleration demands a high petrol level in the jet; We have raised the level as high as .35" down from the spray holes but with the present size choke - 1.925 ins. dia. - the acceleration is not all that is desired. We think however that the choke size can be reduced without impairing the power and this should considerably alleviate the trouble. An appreciably higher level than shewn on the LeC.2286 - where the mean level is at the float fulcrum pin - cannot be employed because of the danger of flooding when the carb. is inclined at an angle, as in an aeroplane standing on the ground. The position of the float chamber relative to the diffuser stand pipes it is thought might influence the performance of the engine when maneouvred violently in the air in a fore and aft direction. The influence of petrol level on rapid acceleration we should expect to be experienced by either the front or rear carbs. if the throttle were suddenly opened from idling with the 'plane in some of the extreme positions frequently assumed by scout machines and at a time when positive acceleration is essential. The appended sketches indicate how the contd :- | ||