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).
Test results and specifications for an engine using long-duration inlet and exhaust cams.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 114 | |
| Date | 31th March 1927 guessed | |
| contd :- -4- (4) Long duration inlet and exhaust cams. The curve for the standard engine with its 4.75 to 1 compression ratio is given for comparison. All these tests were taken with free exhaust - short pipes 7" long were used for each port. 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 RPM. 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 standard inlet and exhaust contours were used but a period of 14º dwell at position of full lift was inserted in the inlet and similarly 6º dwell for the exhaust. This increased the duration of lift measured on the crankshaft by 28º for the inlet and 12º for the exhaust. The cams were arranged so that the exhaust cam led its inlet by 120º. Prints of the cams used for this experiment are appended. A diagram is given shewing the inlet valve displacement plotted on a piston travel base both with contd :- | ||