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).
Camshaft performance tests and variations in cam duration.
| Identifier | ExFiles\Box 82\4\ scan0385 | |
| Date | 1st October 1936 | |
| -8- PART 5. Camshafts. Test No.1. Variation of Cam Duration by Tappet Clearance. Cylinder head EX.20943 at 9 : 1 Comp. Ratio. 6 Amal carburetters 1.187" throttle bore. Standard camshaft EB.1085. Considering graph No. S.5, curve (2). Power is lost at high speeds and gained at low speeds by shortening the duration of the inlet cam. From this one could reasonably assume that power would be gained at high speeds by increasing the duration of the inlet cam. The effect of shortening the duration of the exhaust cam shows the same gain at low speeds by virtue of the decreased overlap, but no loss or gain over the standard shaft at high speeds. Test No.2. 2. 1 5/8" S.U. Carburetters on 1 5/8 induction pipe; otherwise as previous test. From the results of Test No.1, a new camshaft was made, having a standard exhaust cam, and increased duration on the inlet cam, the inlet to open earlier than standard. The result is seen on graph 6, curve No.2, where only a very small increase in power is forthcoming at high speeds. Actually it could be said that this test should have been done using the 6 Amal carburetters as in Test No.1. The answer is, that the time available for this development had to be cut down to the minimum due to pressure of other work, added to which, any gain from any camshaft would be useless unless it could be obtained in conjunction with 2. S.U. carburetters on a proper induction pipe, because of the necessity of keeping in line with the R.A.C. regulations for the T.T. Further to graph No. 6, curve 1, where a variation of timing shows that there is no gain to be obtained from this shaft, as far a slight gain at low speeds there is a loss at high speeds, it being naturally assumed that to move the timing any earlier would result in too much loss at middle speeds for a very small gain at high speeds. | ||