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).
Experiments comparing gas velocities and valve configurations for the 20 HP and Phantom engines.
| Identifier | WestWitteringFiles\R\2October1927-November-1927\ 166 | |
| Date | 24th November 1927 guessed | |
| contd :- -2- Referring to the 20 HP. and Lorraine experiments we have drawn a chart of the conventional gas velocities past the inlet valves on a r.p.m. base and see that for the same rotative speed the Phantom gas velocity is approx. 60% higher than the Lorraine or 20 HP. with the large valves. This indicates we must expect the Phantom with its present valves to give its power peak at a lower speed than the large valve 20 HP. We have found that the valve area - or gas velocity in itself is not the only factor in determining the speed at the power peak. The chief factor appears to be the valve opening duration and timing - a long duration being necessary for power at high speeds. In order to obtain full advantage of the 'duration factor' it is first necessary to employ large valves. Actually we find these two factors are almost inseparable where optimum results are desired. On print No.4. is shewn the effect of large valves and combination of large valves and long duration of valve opening for the 20 HP. We have carried out tests on the Phantom with different camshafts the results of which are given on print No. 5. with particulars of the opening duration and timing. The first experimental camshaft had the inlet duration increased by 26° and the exhaust increased by 12°. This was a definite improvement on the std. at the high speeds. The second experimental shaft had the same inlet duration and timing as the previous one but the exhaust cam and timing was made the same as standard. Although the power output contd :- | ||