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).
Development and testing report on the Phantom semi-expanding carburetter.
| Identifier | ExFiles\Box 13\4\ 04-page175 | |
| Date | 6th November 1932 | |
| X 7080 TO Sg.{Arthur F. Sidgreaves - MD} From Hs{Lord Ernest Hives - Chair}/Dwdl. C. Hor. G.F. Hy.{Tom Haldenby - Plant Engineer} F.H. Ma. Hs{Lord Ernest Hives - Chair}/Dwdl.17/MT.6.11.32. X 7771 PHANTOM SEMI-EXPANDING CARBURETTER (Lec.3432). Development of this carburetter has been carried out on the 8 litre Phantom test bed unit having a compression ratio of 5.5 : 1. It embodies the results of tests carried out on the previous large carburetter (Lec.3137), namely, increased air valve and throttle bore giving a lower induction pipe depression resulting in more power, together with a more straight forward petrol feed to the diffuser and a simpler air valve construction. Comparative curves between - (a) 2 - 1S S.U. carburetters, (b) Semi-expanding carburetter (Lec.3432), (c) now in production, are shown on Hs.{Lord Ernest Hives - Chair}1191. At 3000 R.P.M. the approximate speed of maximum power, the 2 S.U's give 169 H.P. and an induction depression of 1.65" Hg; the large expanding carburetter (Lec.3432) 184 H.P. and a depression of 2.2" Hg; whilst the production model No.S3441 gives 175 H.P. and a depression of 3.35" Hg. Below 1000 R.P.M. the results with both types of semi-expanding carburetters are almost identical and give 2 - 3 lbs/sq.in. M.E.P. above the 2 S.U's figure. The movement of the air valve is ideal, the lift being progressive and steady under all conditions of running. Commencing to lift at 550 R.P.M. full throttle, maximum lift is reached at 2750 R.P.M. and should not be less than .720, otherwise the air flow is restricted. Drawing limits should permit a diametrical clearance of .0035 to .004 between the piston and its chamber. From under the base of the main jet petrol is fed into the stand pipe above the fit of the taper needle in its guide, so that if wear takes place, petrol leaks into the suction line and so prevents air bleeding which would upset considerably the mixture. | ||