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).
Engine performance, focusing on camshafts, valve lift, and detonation issues in various engines.
| Identifier | ExFiles\Box 123\5\ scan0102 | |
| Date | 30th September 1938 | |
| -2- Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}9/WR.30.9.38. Ds/Jnr.{Charles L. Jenner} is going to give alternative camshafts for further trial, also if possible to increase the inlet valve lift. The induction pipe depression of 2.8 ins. at 3500 R.P.M. also confirms that the breathing is not what should be expected from the large inlet valve (1.75 dia.) used in this engine. This adds weight to the fact that the duration and lift, or both, is inadequate. A Wraith engine with 1.6 dia. valves registers an induction pipe depression of 3" at 3500. It is interesting to compare the ratio of valve lift to valve diameter which reveals the B.60 to have the lowest ratio and could, we consider, be raised with advantage. The following are comparisons of the inlet valves:- OHC engine - .36 - 150 BHP B.III " - .200 - 125 " B.60 " - .229 - 117 " It is apparent from the results obtained on the single cylinder, that the optimum timing to give the best results on the single cannot be transferred to the main engine and reproduce the same performance. Detonations. Regarding the low speed end of the curve, although no actual figures have been taken on detonations we can, on Ethyl fuel, run full advance to give maximum power, whereas on Wraith it is necessary to retard, thus losing power to cut out detonations. It is anticipated from this, therefore, that the non detonating power on the B.60 will be equal, if not better than, the non detonating power on the Wraith which is the allowable power in the car. The basis upon which we are going to work is to increase the compression ratio on the B.60 to such an extent that the detonation characteristics are on a par with the Wraith III. | ||