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).
Report comparing engine performance with different camshaft configurations.
| Identifier | ExFiles\Box 6\7\ 07-page091 | |
| Date | 23th May 1931 | |
| -3- HS{Lord Ernest Hives - Chair}/AZ.1/AL.23.5.31.Contd. loading up when running for lengthy periods at low R.P.M. full throttle. We found we could open up the brake to maximum R.P.M. and the engine would speed up without the slightest unevenness. With the Std. six port system, which although an improvement over "Chima", shows a certain amount of hesitation when subjected to this test. All these tests were carried out with 112° long duration camshaft. We then tested the Std. "Chima" 110° camshaft which has shorter duration cams. The 112° was superior from 500 R.P.M. to 1450 R.P.M. but above this speed the 110° gained. Next 112° long duration camshaft was tested and this was definitely superior. Another advantage shown by the long duration cams, was in avoiding valve bounce at 3500 R.P.M. We did not use an oscilloscope but went by sound and evidence of this by the sudden drop in the power curve at 3500 when using the short duration 110° camshaft. The results given on V.448 are for the best valve timings with each camshaft. The results with the 112° camshaft are particularly encouraging because we touch approx. 119 lbs/sq.in. B.M.E.P. at 1750 R.P.M. and still have 100 lbs/sq.in. B.M.E.P. at 3000 R.P.M. This is with 5.25/1 compression ratio. With 5.5/1 compression ratio we ought to touch 121 B.M.E.P. The max. B.M.E.P. occurs at a very useful road speed of approximately 35 M.P.H. On curve V.949 we show the superiority of the 112° camshaft over 110° when used with the twin carburetters also with the Std. chassis carburetter. This curve illustrates | ||