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).
Interpretation of performance curves for masked inlet valves based on different timings.
| Identifier | ExFiles\Box 13\2\ 02-page143 | |
| Date | 31th October 1931 | |
| 17090 To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/KT.31.10.31. MASKED INLET VALVES. Further to Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/KT.29.10.31. Our interpretation of curves Rm.{William Robotham - Chief Engineer}P.30 & Rm.{William Robotham - Chief Engineer}P.31 is as follows:- Both A.{Mr Adams} timings show poor low speed M.E.P. and in both cases the Inlet valve closes 44° A.B.C. with widely different exhaust valve timings. We therefore deduce that owing to the rapid rate of closing of the masked valve, 44° is too late to leave it open if a good low speed M.E.P. is required. Curve B. 112° masked shaft we believe loses low speed M.E.P. because the exhaust opens too early (actually with .013 clnce 61° B.B.D.C.) and for the same reason coupled with the fact that the inlet valve closes slightly early, does not give high speed power. Curve B. 108° we think, gains at low speeds because the Ex. valve opens slightly later than the 112° A.{Mr Adams} timing, and also gains at low speeds through the inlet closing 38.5° A.T.D.C. instead of 44°. It is interesting to note that good top power can be obtained with an exhaust valve opening as late as 41° B.T.D.C., Rm.{William Robotham - Chief Engineer}P.30. A, and for this reason, if we had to establish a timing from these tests we should say that the best would be :- [DIAGRAM] IN 40 EX 65 41 8 12 21 | ||