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).
Analysis of cylinder head temperatures and a performance comparison with Bentley and Rudge designs.
| Identifier | ExFiles\Box 133\1\ scan0117 | |
| Date | 17th September 1936 | |
| -13- Hs{Lord Ernest Hives - Chair}/Ed.{J. L. Edwards}1/KW.17.9.36. Cylinder Head. The head temperatures are fairly uniform at about 120°C. with the exception of the point between the inlet valves. This, however, as will be seen, is situated on a very thin wedge of metal, which, due to the small area by which the heat may be conducted away, and the comparative lack of cooling around the inlet ports, has become unexpectedly hot. In Fig.XXIX the extreme temperature of the plug is almost certainly due to a faulty thermo-couple or plug washer allowing hot gases to come into contact with the couple wires. Comparison with the Bentley. On Fig. XXXIV is shown a comparison between the Rudge, the Bentley standard head, and the Bentley high power head. In order not to confuse the issue, the figures are brought to a standard motoring loss value, the Rudge being taken as standard, by the following method. The B.M.E.P. curves for the standard Bentley and Rudge units are plotted out, and corrections made to bring them to a common C.R. of 7.3. The difference in motoring losses between the Rudge and the Bentley is then added to the latter's power curve, and we obtain a curve which would be given by the Bentley if it had a C.R. of 7.3:1 and a lost M.E.P. equal to that of the Rudge at corresponding piston speeds. We thus have two curves, any differences in which are due to cylinder or cylinder head design giving improved combustion or breathing characteristics. The curve for the High Power Head was obtained in a similar manner. On inspection it will immediately be seen that the maximum power rises with increase in inlet valve size, and it was decided to try and draw a curve showing the maximum M.E.P. with common motoring losses; i.e., correcting all B.M.E.P's so that they give a value for the power which would have been delivered if the unit had had a C.R. of 7.3 and Rudge motoring losses, against the specific inlet area: viz: total inlet valve area/litre. The resultant curve is shown in Fig.XXXV, and figures are as under :- | ||