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 experiments with a long duration camshaft.
| Identifier | ExFiles\Box 5a\5\ 05-page052 | |
| Date | 31th March 1927 guessed | |
| contd :- -4- The max. gain is 30.5 B.HP. or 56%. From the curve we see that we have not yet reached the max. power as the curve is still rising at 3000 r.p.m. The specific petrol consumption is also considerably lower resulting partly from the higher compression ratio. Later tests (as yet incomplete) indicate that the long duration camshaft gives greater efficiency than the std. camshaft, this can probably be accounted for by the lower pumping losses which are likely to result. DETAILS OF THE CAMSHAFT USED: The std. inlet and exhaust contours were used but a period of 14° dwell at position of full lift was inserted in the inlet and similarly 8° dwell for the exhaust. This increased the duration of lift measured on the crankshaft by 25° for the inlet and 12° for the exhaust. The cams were arranged so that the exhaust cam led its inlet by 12°. Prints of the cams used for this experiment are appended. A diagram is given showing the inlet valve displacement plotted on a piston travel base both with the std. and long duration cams in positions of the best timing. The greater opening at and after bottom dead centre to take advantage of the kinetic energy of the gases built up during the earlier part of the stroke is clearly shown. SUMMARY: (1) A camshaft with long duration inlet and exhaust cams resulted in an increase in max. B.HP. of 21%. contd :- | ||