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 and analysis of 3-port and 4-port exhaust manifolds with and without silencers.
| Identifier | ExFiles\Box 86\3\ scan0217 | |
| Date | 13th April 1938 | |
| -3- When a single silencer is fitted, however, (Curve C) power is better with the 3 port manifold than with the 4 port. The former dropping 34 BHP and the latter 39 BHP at 4000 r.p.m., an average drop of 24.5% over the open exhaust figure of 149 BHP at 4000 r.p.m. Whilst at the low speeds the BMEP is slightly higher with the 4 port manifold. Continued. GRAPH TEXT: B.23.O.H.C. VALVE TIMING I.O 2°BT{Capt. J. S. Burt - Engineer} E.O.43° B.B. I.C 33°PB E.C.12° P.T. LB.8. PLUGS TAPPETS AT .006" ETHYL FUEL LEGEND: OPEN EXHAUST 4 PORT MANIFOLD + 1 SILENCER 3 PORT MANIFOLD + 1 SILENCER CURVE LABELS: M.E.P. B.H.P. C DIAGRAMS: 3 PORT To BENTLEY SILENCER 4 PORT To BENTLEY SILENCER AXIS LABELS: R.P.M. | ||