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).
Performance comparison between the 'Ramp' cylinder head and the standard head, focusing on detonation and power output.
| Identifier | ExFiles\Box 133\2\ scan0061 | |
| Date | 26th July 1934 | |
| -3- Generally speaking, the Ramp head is considerably worse than the std. for freedom from detonation: at 1600 r.p.m. the audible range of detonation of the former is 113 feet, while the latter is 60 feet; at 2200 r.p.m. the Ramp is still 87 feet, while the std. is zero. The Ramp is not entirely free from detonation until a speed of 3500 r.p.m. is reached. These results will be found in more detail on sheets 2 and 3 of the appended curves. Sheet 2 refers to the Ramp head and gives curves of (a) the detonation intensity at max. power with weakest mixture and minimum necessary advance, (b) the B.M.E.P's corresponding to curve (a), and (c) curves showing B.M.E.P. at constant detonation intensity. On the same sheet are given curves showing the necessary ignition adv. corresponding to the B.M.E.P. curves. The detonation tests of the std. head are given on sheet 3, upon which will be found consumption loops with detonation figures attached, also curves showing B.M.E.P., detonation intensity and required ignition advance. A direct comparison between the Ramp and std. heads is given on sheet 1. On this sheet will also be found a B.M.E.P. and B.H.P. curve of the Ramp head when the detonation is reduced to the level of the std. head. From these curves it will be seen that a maximum power loss of 10% (between 2100 & 2300 r.p.m.) is experienced with the Ramp head under these conditions; and that a speed of 3100 r.p.m. must be exceeded before any gain in power is apparent. Power Comparison. A direct power comparison between the Ramp and std. heads is shown on sheets 4 & 5, the former referring to normal fuel (Shell No. 1) and the latter to anti-detonating fuel (DTD.224). From these curves it will be seen that the Ramp head gives an increase of approx. 10% at the peak of the power curves, the peak speed being raised from 3800 to 4000 r.p.m. At 4500 r.p.m. the Ramp shows an increase of 14.5 % over the std. The higher compression ratio of the Ramp is responsible for approx. 1 % of the increase. The adverse effects of detonation on power is seen on sheet 4, where the std. head is shown to give the more power below about 2800 r.p.m. When running on better fuel (sheet 5) the Ramp shows an increase in power throughout the speed range. | ||