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).
Description of the operation of an automatic choke and carburettor system under various engine conditions.
| Identifier | ExFiles\Box 7\4\ X 608 Carburetter-page52 | |
| Date | 11th January 1939 | |
| -2- In this condition the throttle is held open in a fast idle position by whichever of the three cams is most suitable. As the speed of the engine increases the vacuum line G from the induction pipe to the inside of the thermostat bellows comes into play opening the choke butterfly a further amount. If the throttle be now snapped fully open this vacuum is destroyed and the butterfly closes to its initial setting thus giving the temporary richness required while the engine is revving slowly cold at full throttle. As the engine speed increases under these full throttle conditions the butterfly is pulled open against the torsion spring. (3) Running conditions. The choke is now held fully open by the thermostat and the carburetter operates as a purely standard carburetter in the running condition. (4) Engine cool after running. As the engine cools down the thermostat bellows are allowed to expand, returning the linkage, pick up lever etc. towards their original positions. This continues until the fast idle adjustment screw E comes up against the fast idle cams C (see sketch 4). The throttle pedal must not be kicked in order to allow the choke butterfly to close completely and to set the throttle in the fast idle position. The system is then again ready for cold starting as shown in sketch (1). The foregoing scheme is a mock up carried out with the standard parts available. It is desireable that the thermostat should be operated by heat at the induction pipe rather than at the cylinder block. Hence for a neater and more efficient layout it would be necessary to have an induction pipe casting designed to take a thermostat unit. Further for any system of automatic carburation to work really efficiently without unduly jeopardising petrol consumption it is desirable to have the water temper- Cont'd.{John DeLooze - Company Secretary} | ||