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).
Investigation into irregular firing and exhaust explosions related to carburettor mixture and ignition timing.
| Identifier | ExFiles\Box 1\3\ B001_X 93-page62 | |
| Date | 23th August 1926 | |
| Contd. -3- HS{Lord Ernest Hives - Chair}/ACL1/T23.8.26. If, however, the throttle is slightly closed the explosions will start again. An explanation of this is that the rich mixture from the carburetter combined with the residuas will produce an ignitable charge, but when the throttle is slightly closed the proportion of "live" charge is so reduced as to result in irregular firing and the building up of "missed" charge in the exhaust manifold. It is found that the more the throttle is closed the more the jets have to be strengthened, and as the suction on the carburetter is very small with small throttle openings it is difficult to obtain sufficiently rich mixture. Probably a bye-pass jet near the edge of the butterfly throttle and coming into action as the throttle closed would be fairly effective but would be liable to interfere with the normal action of the carburetter. Early ignition timing:- As the trouble is caused by the charge escaping burning in the cylinders it was thought that with very early ignition timing the chance of igniting the charge would be increased. This was increased to as much as 120º B & C, but the firing was quite as irregular and exhaust explosions were every bit as bad. Contd. | ||