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 engine power output, detonation, and valve timings at various RPM settings.
| Identifier | ExFiles\Box 133\2\ scan0117 | |
| Date | 1st November 1934 guessed | |
| - 5 - POWER OUTPUT WITH HIGH SPEED TIMING. The power curves given on sheet 6 show the effect of timing the valves to give maximum power at 4000 RPM. It will be seen that this timing gives a slight increase in power between 3550 and 4200 RPM., at the expense of a loss of 3.0 lbs/sq.in. MEP. at 2950 RPM. and of 4.0 lbs/sq.in. at 4500 RPM. The chain-line curves on sheet 6 represent the power output with the optimum 4000 RPM. timing with no overlap. The serious loss of MEP. at the lower speeds will be noticed. DETONATIONS. The curves on sheet 7 give a detonation comparison on the "close-centres" with the standard head when the normal Bentley timing is used, from which it will be seen that the former head is the better. Curves showing the comparison when using the 3000 RPM. timing will be obtained at the first opportunity. VALVE TIMINGS. The following valve timings have been used during the tests covered by this report and they are given here for ease of comparison. - | No. | Description | I.O. | I.C. | E.O. | E.C. | Overlap. | |---|---|---|---|---|---|---| | 1. | Normal Bentley ............ | 4°E | 51°L | 51°E | 7°L | 11° | | 2. | " " but overlap limited to 6° | 2°E | 51°L | 51°E | 4°L | 6° | | 3. | " " but with zero overlap | 1°L | 51°L | 51°E | 1°L | 0° | | 4. | "3000 RPM" but overlap limited to 12° | 10°E | 37°L | 53°E | 2°L | 12° | | 5. | "3000 RPM" but overlap limited to 6° | 7°E | 37°L | 53°E | 1°E | 6° | | 6. | " " but with zero overlap | 4°E | 37°L | 53°E | 4°E | 0° | | 7. | "4000 RPM" unlimited overlap | 24°E | 49°L | 67°E | 15°L | 39° | | 8. | " " but with zero " | 2°L | 58°L | 67°E | 2°L | 0° | | ||