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 report on carburettor testing, focusing on acceleration issues, slow-running fuel supply, and proposed choke modifications.
| Identifier | ExFiles\Box 13\3\ 03-page393 | |
| Date | 3rd March 1932 guessed | |
| -2- It is usually found that trouble with opening up and acceleration only appears when the choke is increased to provide about the last 25 to 30% power. We have therefore made some chokes to try out which should provide about 75HP or about 80% the full engine power leaving the other 50% to come from the extra air past the air piston. These chokes are to be tested next. S. is supplying us with a balanced type air piston for test which will be arranged so that the induction pipe depression is not felt directly on the face of that part of the air piston which admits air when the throttle is suddenly opened from slow running. It is the initial 'jump' open of the air piston which appears to cause the trouble. This scheme will be tested immediately after the trial with the larger chokes. The slow running fuel in this carburetter is taken direct from the float chamber which is difference to our aero practice where this supply is taken from the base of the diffuser. On this carburetter we have experienced momentarily excessive richening of the mixture - to the extent of black smoke at the exhaust - when the engine is quickly throttled down to slow running which we have traced to the high suction on the throttle edge slow running which is continuously in action. A test was made in which the slow running supply was taken from the base of the diffuser in the same way as our aero carburetter - and Twin Choke P.II carbs - and completely overcame the trouble. By coupling the slow running jet to the diffuser by a glass pipe we were able to observe that the supply ceased and then reversed when the throttle was quickly opened and it is interesting to note that acceleration is appreciably improved which we think due to the severe flow from the idling system acting in the form of delayed priming while accelerating. From these tests we think it necessary to provide the slow running from the diffuser base as in our aero and twin choke carbs. SUMMARY. Results of the tests show the carburetters to be quite promising. The features we now wish to concentrate on are:- (1) Test out larger size chokes to see if this gives better snap opening due to the transference of a larger portion of the total air flow through the choke containing the diffuser. These tests are now in hand. | ||