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).
Engine smoothness and turbulence, comparing two high power head designs via ignition advance curves.
| Identifier | ExFiles\Box 134\1\ scan0053 | |
| Date | 13th December 1937 | |
| (II) SMOOTHNESS Turbulence is undoubtedly another factor influencing power output, but an examination of ignition curves (Fig.II) seems to indicate that, whilst it no doubt had an effect in previous heads with a varying throat area, if this latter item is kept constant the degree of turbulence is only very slightly effected and ignition advance characteristics will remain about the same. Thus we should expect the combustion smoothness properties of Nos.4 and 5 heads to be about the same and on a par with the standard Bentley. HIGH POWER HEAD FIG II IGNITION ADVANCE CURVES IGNITION ADVANCE -RPM- ① NO.4 HEAD - INCLINED INLET VALVE (1.750" DIAM) C.R. = 6.3 ② NO.5 HEAD - SEMI - INCLINED INLET VALVE (1.750" DIAM) C.R. = 6.3 VALVE TIMING - I.O. 2° E; I.C. 28° L; E.O. 51° E; E.C. 7° L. | ||