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 comparison graph for an O.H.C. Bentley unit with different manifold and silencer configurations.
| Identifier | ExFiles\Box 97\1\ scan0134 | |
| Date | 11th March 1938 guessed | |
| CURVES SHOWING COMPARISON BETWEEN - 4 PORT MANIFOLD TWO DOWNTAKES & 1 SILENCER - 3 PORT MANIFOLD TWO DOWNTAKES & 1 SILENCER. O.H.C. BENTLEY UNIT B 23 L.B. 8 PLUGS ETHYL FUEL NO AIR SILENCER TAPPETS AT .006" VALUE TIMING WITH .020" CL'CE I.O. 2° B.T. E.O. 43° B.B. I.C. 33° P.B. E.C. 12° P.T. 1 5/8" CARBS. ① OPEN EXHAUST ② 4 PORT MANIFOLD WITH TWO DOWNTAKES INTO 1 BENTLEY SILENCER SYSTEM ③ 3 PORT MANIFOLD WITH TWO DOWNTAKES INTO 1 BENTLEY SILENCER SYSTEM 4 PORT 3 PORT FRONT EXPANSION BOX OF BENTLEY SILENCER. B.H.P. B.M.E.P. BMEP LBS/☐" R.P.M. 20" BACK PRESSURE INS. MERCURY 10" 0" BACK PRESS FOR ② & ③ PRACTICALLY THE SAME E | ||