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).
Comparison of M.E.P. gains and power gains between various Bentley engine cylinder heads at different RPMs.
Identifier | ExFiles\Box 134\2\ scan0064 | |
Date | 15th July 1935 guessed | |
-4- A second comparison is given in Fig.IV. This shows the standard small bore Bentley head EB.615 against its exact equivalent on the single cylinder unit, with a third curve showing the approximate form when the single is run under main engine conditions of induction depression. We observe from this that there are the following M.E.P. gains of the single over the main engine :- 2000 R.P.M. 0.08% 3000 " 6.8% 4000 " 11.0% 4500 " 12.5% and these figures will be borne in mind when estimating the advantage of the High Power head. Referring now to Fig.III, we have a direct comparison between the high power head, the T.T. head and the standard large valve Bentley head. The high power head has been reduced to main engine depressions, and then further modified by applying the above correction figures for power discrepancies between main engines and single cylinders. We thus have a fairly comparative set of curves. We see, now, on inspection that there is a slight gain in power of the high power head over the T.T. head, which when we consider that the only modification to this latter curve is to alter the C.R., making no allowances for induction or friction, is a very promising result. The gain over the standard head is very considerable, as is seen by the following figures :- 1000 R.P.M. 6.0% 2000 " 4.5% 3000 " 10.0% 4000 " 21.0% 4500 " 23.0% These results are borne out by the figures quoted at the beginning of the memo. | ||