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).
The disadvantages and potential modifications for the Bentley V, S.U. Startex carburetter.
| Identifier | ExFiles\Box 99\1\ scan0061 | |
| Date | 21th February 1940 | |
| -2- Bentley V.{VIENNA} S.U. Startex carburetter. In view of the possibilities of having to fit the S.U. startex to our engines the following facts concerning its possible modification and development have been put down. The two major disadvantages of the startex are (a) The difficulty of obtain good distribution of the starting fuel, and (b) Its ability to freeze up. Freezing up can occur in two ways - (a) If the car is left out in a humid atmosphere with the thermometer standing below freezing point, the startex needle may freeze in the rich position which it should normally hold only until the engine fires. This may also mean that ice has formed at the needle disc thus restricting the air flow through this annulus and making the mixture even richer. (b) If the car is started cold in a humid atmosphere, not necessarily below freezing point but maybe at +5°C, the engine may run satisfactorily for a time. Due to the humidity and cooling due to vaporization of the fuel, ice will probably build up on the needle disc and in the spring beneath it. This will, of course, strengthen the mixture, and if the car is not driven away, will ultimately stop the engine. Of the two conditions of freezing one may say that (a) is by far the less serious. Whereas weather conditions may be suitable for weeks on end to freeze the startex under condition (b), condition (a) requires very low temperature and a humidity with which this temperature is not generally associated. Two means of overcoming the trouble have been tried - (1) With the needle which we use, the needle disc diameter is 0.435" giving an annulus of .0325" for the passage of air. The disc diameter we increase | ||