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).
Performance graph and analysis comparing different exhaust manifold and silencer configurations.
| Identifier | ExFiles\Box 86\3\ scan0219 | |
| Date | 13th April 1938 | |
| B 23 OHC. VALVE TIMING I.O. 2° B.T. E.O. 43° B.B. E I.C. 33° P.B. E.C. 12° P.T. L.B.8 PLUGS. TAPPETS AT .006" ETHYL FUEL OPEN EXHAUST 4 PORT MAN'D WITH 2 DOWN'TKS INTO 1 SIL'R 3 PORT MAN'D WITH 2 DOWN'TKS INTO 1 SIL'R B.H.P. & M.E.P. R.P.M. M.E.P. B.H.P. 3 PORT 4 PORT FRONT EXPANSION BOX OF BENTLEY SILENCER The power drop when using two downtakes into one front expansion box is 24.5 HP or 16.5%. This compares with 12 HP or 8.06% for two silencers in parallel, and with 36.5 HP or 24.5% for one silencer with single downtake from manifold, and is almost exactly half way between the two. The 4 port manifold was then divided between Nos. 2 and 3 ports, and in conjunction with two silencers in parallel, the power given was the same as when there was no division. The open exhaust power given by this unit was 149 BHP at 4000 r.p.m. 5.6 HP or 3.76% is lost in the 6 port manifold (the cast manifold designed for the O.H.C. unit). When the 6 port manifold was moved along the head, so that the first three ports were open, and the last three were exhausting through the manifold, the power loss was only .06 HP, but with the addition of a silencer to the last three ports with | ||