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).
Summary of test results regarding engine valve timing for optimal power across different speeds.
| Identifier | ExFiles\Box 98\5\ scan0016 | |
| Date | 12th April 1938 | |
| -2- The attached curve shows overlap diagrams. Previous tests have shown that - (a) For good top power effective closing of exhaust valve on heavy acceleration should be after T.D.C. (b) Overlap between inlet open and exhaust close good for top power and not detrimental to low speeds full power limit being required standard of idling. (c) Inlet closing not critical to top power, early closing gives best low speed power. (d) Exhaust opening has to be compromised late being good for top power and early for low power. (e) Varied duration and timing of exhaust valve makes little difference to the percentage power loss with an exhaust system. (f) Engines with good breathing register highest percentage power loss to exhaust systems. (g) Duration on toe sufficient to reduce appreciably the low speed power with little advantage to top power, therefore toes should be as short as possible consistent with quiet operation of valves. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||