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 testing, comparing performance with different camshaft durations and carburetter configurations.
| Identifier | ExFiles\Box 5\4\ 04-page237 | |
| Date | 23th May 1930 | |
| -3- Hs{Lord Ernest Hives - Chair}/ACL.1/ML.23.5.30.Contd. 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 "China", shews a certain amount of hesitation when subjected to this test. All these tests were carried out with 116° long duration camshaft. We then tested the Std. "China" 110° camshaft which has shorter duration cams. The 110° was superior from 500 R.P.M. to 1850 R.P.M. but above this speed the 116° gained. Next 112° long duration camshaft was tested and this was definitely superior. Another advantage shewn 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.868 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.869 we shew the superiority of the 112° camshaft over 116° when used with the twin carburetters also with the Std. chassis carburetter. This curve illustrates the very appreciable gain possible with twin carburetters | ||