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).
Valve lift coefficients and port shape effects for Kestrel, Merlin, and car size cylinders.
| Identifier | ExFiles\Box 134\2\ scan0053 | |
| Date | 30th October 1935 | |
| - 2 - CURVES 11, 111 & 1V give the coefficients at various valve lifts for Kestrel, Merlin and car size cylinders respectively. In these curves the effect of the port shape can be seen, for instance, in Curve 11, the ramp inlet valve gives 50% more flow than the Kestrel at maximum lift. The inlet plug ramphead after one test was modified to Lec.4577 by smoothing the inlet valve guide bosses etc. giving a 5% increase in flow at maximum lift. This can be seen in Curve 111. From Curve 1V the Rudge engine would appear to have a very poor port shape. This is due to the narrow throat between the carburetter and the valves which would seem to be necessary for good atomisation in this short space. A peculiarity of this port was a shrill whistle at a certain valve lift, caused by the sharpe edge of the port bar between the valves. From these Curves it can be seen on which engines the valve lift could be increased or reduced with advantage. In order to represent these results on a numerical basis, performance factors for the various engines have been calculated and are given in the following table. The R.P.M. factor is K at max. lift cylinder volume and would represent the r.p.m. at peak power while the piston speed factor is K at max. lift piston area and would represent the piston speed at peak power. (Table given on following page) | ||