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).
Analysis of experimental camshafts, focusing on inlet duration and valve timing.
| Identifier | ExFiles\Box 102\5\ scan0124 | |
| Date | 18th April 1932 | |
| E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} C. By.{R.W. Bailey - Chief Engineer} ________ X5090 x7090 HS{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}2/IA.18. 4. 32. CAMSHAFTS. We attach a complete analysis of the best camshafts that we have tried experimentally. The main point about J.III camshaft is that it does not follow the practice that has been established on P.II. On China we had a restricted induction system and so a short duration inlet did not worry us very much. On J.III, however, we think the inlet duration should be about 228º which conforms closely with the P.II 230º and also with the very satisfactory experimental camshaft (No.2) that we made out of two exhaust cam forms. We had run camshafts No.2 and No.3 on a J.I engine with the two R.R. carburetters, and camshaft No.2 gives a better M.E.P. over the whole range culminating in a gain of something over 6 B.H.P. at 3500 R.P.M. INLET CAM. This all goes to confirm R's recent agreement in R.1/M.18.3.32. that the exhaust and inlet cam can with advantage be about the same duration. We believe in our own mind that it is of vital importance to open the inlet valve at the earliest possible moment. You will recollect that on the P.II with the two S.U. carburetters and camshaft No.5, with the inlet opening at 2.2 A.T.C. there was no sign whatever of roar, and we therefore think that with a resonance type intake silencer we should be able to open the inlet valve at this point. With regard to the inlet closing, if we open at T.D.C., we can close up to about 48 A.B.C. without losing much low speed M.E.P. | ||