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 a downdraught twin Solex carburettor with a central water-heated manifold.
| Identifier | ExFiles\Box 102\1\ scan0282 | |
| Date | 7th May 1935 | |
| To Rm.{William Robotham - Chief Engineer} c. to Hs{Lord Ernest Hives - Chair}/CTS.{C. Trot Salt - Carburation} Hs{Lord Ernest Hives - Chair}/GR.{George Ratcliffe}14/KW.7.5.35. 18-G-IV. Downdraught Twin Solex with Central Water-Heated Manifold. The low speed jets were found to be too large for road work and were reduced from .021" & .023" to .015" both. Acceleration is O.K. except between 5 & 20 m.p.h. with the accelerator pump disconnected; carburation being far too strong at intermediate speeds with it connected. With tappet clearances at .005", fairly even slow running obtained at 5 m.p.h., engine occasionally lumpy. With tappet clearances at .010", fairly even slow running obtained at 3 m.p.h., engine occasionally lumpy without affecting the motion of the car to any extent. No appreciable difference between .015" than .010" clearance. Running idle at .005" engine was very uneven. Running idle at .010" engine was still uneven. Running idle at .015" engine was still uneven. The uneven slow running is mainly due to wet spirit entering the ports before being vaporised in the manifold. This is followed out by the fact that good even slow running is obtained for a very short period, immediately after clearing the manifold out by racing the engine, and that no improvement is obtained by reducing valve overlap from .010" to .015" clearance. This arrangement is not as good as the downdraught Stromberg, which in turn was an improvement on the twin SpectreCodename for Phantom III carburetters mounted on the standard Bentley manifold to the extent of 3 1/2 m.p.h. to 4 m.p.h. even slow running. Hs{Lord Ernest Hives - Chair}/G.Ratcliffe. | ||