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).
Technical comparison of various engine cylinder head designs, including Ramp, Penthouse, Kestrel, and Bentley types.
| Identifier | ExFiles\Box 134\2\ scan0040 | |
| Date | 30th May 1935 | |
| -5- E/PSN.2/MN.30.5.35. the results do not show the improved breathing capacity which would be anticipated but this may have been due to the timing which was the same as for the Ramp Head and probably unsuitable for the larger valves. However this head showed several unexpected characteristics and it is hoped to explore it further on the universal Unit. (5) Kestrel Four Valve Ramp and Bentley Two Valve Ramp Head. It is interesting in comparing the two valve and four valve Ramp Head designs to note that they have very similar inlet areas and very similar performances, compared on an i.m.e.p. basis, although the cylinders are very different in size and run at very different R.P.Ms. It is a confirmation if any is necessary, that performance is governed by valve area or actually inlet gas velocity and piston speed, and on such a basis cylinders of all sizes and stroke bore ratios can be compared. (6) Ramp and Penthouse Cylinder Heads. It is possible to obtain slightly greater valve area on a Penthouse than on a Ramp Head. A direct comparison of the two heads will be made for the Merlin 'D' size on the Universal Unit. In conclusion it should be emphasised that these comparisons are between breathing capacity only, and in order to obtain comparisons of power output the effect of compression ratio must be taken into accout. In general it is possible to run the sleeve valve engines at between .75 and 1 compression ratio higher than the poppet valve engines which would mean a gain of between 7 and 9 m.e.p. for the sleeve valve engines. E/PSN. | ||