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).
Cold starting issues with the R.R. Phantom II Semi Expanding Carburetter, detailing modifications made to improve performance.
| Identifier | ExFiles\Box 13\4\ 04-page039 | |
| Date | 28th September 1932 | |
| X7080. E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/CTS.{C. Trot Salt - Carburation} c. to BY.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/CTS.{C. Trot Salt - Carburation}1/KT.28.9.32. R.R. P.II. SEMI EXPANDING CARBURETTER. Starting Up (Cold). On Experimental cars fitted with the Semi Expanding carburetter, trouble has been experienced starting up from cold. Under the present conditions, the arrangement of the slow running choke is such that a good start can only be made when the two following adjustments are correct. Firstly, the L.S. choke must be definitely seating on the jet, in the full strong position. Secondly, the throttle opening must be at that point at which the maximum suction is obtained at the throttle edge. Beyond this point the mixture is excessively weak (on the low speed range). By increasing the jet from .031 to .039 dia. and the two holes at the throttle edge from .075 to .080 dia, the desired rich mixture is obtained, but the range on the mixture control is not sufficient to obtain the necessary weakening. A new piece V.1414 has been tried in which the choke dia. is increased from .156 to .250 dia, and the annular area between the slow running sleeve and passage of the carb. body increased in order to make the air supply more effective. In the modified sleeve (V.1414,) the central copper choke has been done away with, and the one piece unit now performs the same operation. The initial setting of the low speed choke is done by an adjusting washer, the thickness of which will determine just where the choke will start to lift in conjunction with the movement of the mixture control. Hs{Lord Ernest Hives - Chair}/C.T.Salt. | ||