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).
Past experiments and future considerations for improving engine volumetric efficiency, camshaft duration, and idling.
| Identifier | ExFiles\Box 124\2\ scan0394 | |
| Date | 5th February 1944 | |
| 1044 To: CJS. from Rm.{William Robotham - Chief Engineer} c. to Jnr.{Charles L. Jenner} c. to Ev{Ivan Evernden - coachwork}/MGA.{M. G. Aspley} Rm.{William Robotham - Chief Engineer} 2/h.{Arthur M. Hanbury - Head Complaints} 5.2.44. B.80. VOLUMETRIC EFFICIENCY. I was disappointed with your summary of the problem of improving the volumetric efficiency of the engine. At various times, since 1920, we have tried : (a) High and low lift camshafts P.II. (b) High and low lift rockers - Bentley. 1. CAMSHAFT DURATION. We have tried long duration camshafts on : (a) P. II. (b) Bentley. We had Merlin duration on the T.T. engine. (c) Peregrine. (d) B.60. engine. It is quite certain that after a certain point is reached, further increase in duration produces little increase in top H.P. but an appreciable drop in low speed torque. To the best of my recollection, valve area is interchangeable with camshaft duration - that is, the better the valve area/litre - the less benefit from a long duration shaft. I believe Tan's engine, in spite of its good output, had a relatively short duration shaft. 2. IDLING & DISTRIBUTION. I am under the impression that the size of induction pipe can affect idling, and Wyn. carried out some experiments and can provide information on the subject. I think it will be found, however, that within the limit of pipe size required to give good snap opening, the effect on idling will not be great. In any event, we have just put 2 S.U. carburetters on the B.40. and on a 2-port engine this must largely eliminate distribution trouble. Hence we can immediately get a figure of merit for distribution on this engine which you now have on the test-bed. | ||