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).
Camshaft performance and proposed modifications for the B.III engine unit.
| Identifier | ExFiles\Box 98\5\ scan0015 | |
| Date | 12th April 1938 | |
| By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} SECRET Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}2/AP.12.4.38 c. Da.{Bernard Day - Chassis Design} c. HFS. CAMSHAFT - B.III. As shown in our previous report, the B.III. unit, although developing the same maximum power (open exhaust) as the present production Bentley, falls off more rapidly above this speed. Irrespective of other variations in the two engines and by comparison of B.III. camshaft on B.II unit against its own normal shaft, we know that the short duration B.III. shaft does tend to produce this fall off in power at high speeds. Without affecting the best results of the B.III. shaft, i.e. good middle speed M.E.P. and good slow running by virtue of minimum overlap we think by experience the camshaft could be modified to give some increase in power at high speeds. At the present time all the valve noise heard is that of seating, therefore we consider that the opening rate of toe could be increased thus reducing the overlap at running clearances and brought back again to the original figure by increasing the main duration of the exhaust to improve the scavenging at high speeds. In actual figures the cam modification requirements are:- (1) Opening toe velocities on inlet and exhaust to be increased from .00825 to .0012. (2) Duration over high accelerations on inlet cam as existing on inlet, i.e. 242°. (3) Duration over high accelerations on exhaust increased to 247°. (4) Angle between ℄ of cams 111°. (5) Valve timing at .030 clce. I.O. - T.D.C. E.C. - 5° past TDC. I.C. - 45° E.O. - 45° before B.D.C. (6) Other than above valve lift diagram as LeC.5426. continued | ||