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).
Comparative analysis of engine performance metrics (BMEP, RPM) for different inlet valve and camshaft configurations.
| Identifier | ExFiles\Box 133\1\ scan0118 | |
| Date | 17th September 1936 | |
| -14- | Unit | Inlet dia. | Inlet Area | Area/Litre | Max. BMEP | BMEP C.R.= 7.3. | BMEP with Rudge Losses | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | Rudge | 2 - 1.200 | 2.26 in.² | 4.50 in.² | 164 | 164 | 164 | | Standard Bentley | 1 - 1.400 | 1.54 " | 2.50 " | 125 | 129 | 144 | | High Power | 1 - 1.750 | 1.41 " | 3.91 " | 139 | 139 | 158 | | High Power | 2 - 1.225 | 2.36 " | 3.86 " | 140 | 140 | 159 | | Ramp No.2 | 1 - 1.500 | 1.86 " | 2.88 " | 135 | 139 | 158 | | Ramp No.2 | 1 - 1.600 | 2.00 " | 3.26 " | 136 | 140 | 159 | It will be observed that the points lie roughly on a curve which is tending to flatten out, and it appears probable that 4.500 in.² to 5.00 in.² is about the maximum specific valving which will give an increase in power. Beyond this point the curve will flatten out, leaving pressure induction as the next step to increase volumetric efficiency. Whilst this power increase may be reached, it is not improbable that valve sizes will be influenced by other items such as tick-over, slow running at full and part throttle, etc. This is to some extent borne out by the Rudge, and the minimum speeds at which it was possible to run at full throttle, together with the valve overlaps and maximum M.E.P's are given below. Max. B.M.E.P. Valve Overlap Minimum Full Throttle R.P.M. 164 53° 3000 152 11° 2500 141 - 11° 2000 and a power comparison with the various camshafts is shown on Fig. XXXVI. | ||