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).
Experiments investigating factors that affect engine acceleration, specifically carburettor performance.
| Identifier | ExFiles\Box 42\3\ Scan026 | |
| Date | 11th November 1926 guessed | |
| contd :- -2- EXPERIMENTS TO SHEW FACTORS AFFECTING ACCELERATION. We will first describe what we have found happens in the carburetter when the throttle is opened slowly. The idle jet supplies mixture from the lowest speed up to about 2000 RPM. As the idling speed is increased by opening the throttle the petrol in the accelerating well outside the diffuser falls below the level in the float chamber while that in the centre of the diffuser tube rises. When the speed reaches approx. 1200 r.p.m. fuel is sprayed through the nozzle. If the throttle is opened suddenly the idling supply momentarily ceases due to the loss of depression behind the throttle and there is a small time lag before the petrol issues through the spray nozzle. This point was proved by using a glass tube in the idling system. It is at this instant that the engine either 'cuts out' or hesitates and back-fires. We have evidence that the accelerator well supplies a rich mixture if we open the throttle suddenly after the sprayer is in action when rapid acceleration results accompanied by puffs of black smoke from the exhausts. It seems evident that the trouble is not due to the quality of the mixture from the diffuser but to the time lag before it comes into action. Experiments were therefore directed towards finding a means of reducing the time lag of the sprayer when operating under sudden demand and of preventing the 'cutting out' of the idler supply. contd :- | ||