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).
Carburetter and engine performance, focusing on issues with throttle bias and fuel distribution.
| Identifier | ExFiles\Box 123\1\ scan0078 | |
| Date | 27th January 1941 | |
| 1086 To Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} c. to Ev.{Ivan Evernden - coachwork} c. to Jnr.{Charles L. Jenner} c. to Rm{William Robotham - Chief Engineer}/OTS. c. to Rm{William Robotham - Chief Engineer}/Wym.{G. Harold Whyman - Experimental Manager} Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden}3/ET.27.1.41. "Notes on Carburetter and Engine." In the following notes a case is made for turning a fixed choke carburetter through 90°, and thus creating throttle bias if circumstances demand it. Circumstances are thought to demand it when, although the carburetter is mounted so as to give no throttle bias, the rocking of the engine causes the float to bounce, and the fuel level to rise. Hitherto the method of overcoming this has been to drop the fuel level in the carburetter. This creates a flat spot which it is impossible to completely overcome. It is shown that although distribution may be correct on the test bed, it may be considerably upset during acceleration, and in fact, forward throttle bias may improve accelerating distribution at part throttle. It is argued that since part throttle acceleration is the limiting condition for carburetter lean-ness, it is more important to have correct distribution under these conditions than under any other. Finally it is alleged that on the non-aero type carburetter with the float fitted to the front (giving no throttle bias) a mixture far too strong is fed to the rear cylinders on full throttle acceleration, resulting in an actual drop in acceleration. This type of carburetter is also notorious for flooding on gradients when mounted in this way. Rm{William Robotham - Chief Engineer}/TAS.{T. Allan Swinden} | ||