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).
Test report on the Large Phantom II Semi Expanding Carburetter, detailing modifications and performance.
| Identifier | ExFiles\Box 13\4\ 04-page099 | |
| Date | 6th February 1933 | |
| E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell} c. to BY.{R.W. Bailey - Chief Engineer} X7080 Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}5/MA.6.2.33. LARGE PHANTOM II SEMI EXPANDING CARBURETTER. Preliminary tests have been carried out with the larger carburetter (Lec.3137) and shows a reduced induction pipe depression from 3.5 Ins.Hg. to 2.6 Ins. Hg. at 3000 R.P.M., full throttle, the former figure being the figure obtained with the existing production carburetter (E.83441). As yet the power increase by the reduced induction depression has not been directly compared under identical conditions. Attached curve (V.1508) shows the power output obtained with the larger carburetter when running with open exhaust, 5.25 compression ratio and 114° high lift camshaft (E.32448). By completely removing the suction piston, the depression is reduced from 2.6 Ins.Hg. to 2.2 Ins.Hg. at 3000 R.P.M. These figures appear to indicate that to further reduce this depression, a still larger suction piston should be accompanied by an increased throttle bore. A small increase, say from 2.25 diameter to 2.375 diameter the free area between the small venturi and the throttle bore being materially increased from 2.44 sq.in. to 2.90 sq.in. Suction Piston. As designed with the suction hole in the side of the throttle body in close proximity of the butterfly, the piston was fully lifted at 2000 R.P.M. In addition to lifting too early the movement was not progressive with the throttle position and became unstable in action. By taking the suction hole from the intake body the fully lifted speed was raised to 2500 R.P.M. full throttle and though an improvement, the movement was not as consistent as desired. Finally the suction was taken past the clearance between the piston and its chamber by blanking off the other definite suction holes. In this form the movement of the piston as shown on (V.1508) is almost ideal, commencing to lift at 750 R.P.M. full throttle and being fully lifted at 3000 R.P.M. Together with full throttle conditions, the piston was directly variable with varying throttle openings and perfectly stable in action. | ||