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).
Detailed report comparing the performance of standard and No. 2 Ramp Bentley cylinder heads.
| Identifier | ExFiles\Box 133\2\ scan0078 | |
| Date | 11th October 1934 guessed | |
| (2) DETAILED REPORT. VOLUMETRIC EFFICIENCY. Air consumption figures have been recorded for the standard Bentley Cylinder Head and No.1 Ramp (LeC.3739). These were obtained by means of measuring the pressure drop across a sharp edged orifice through which the induction air passed. A large capacity reservoir was interposed between the orifice and the carburetter to damp out the pulsations. The results of these tests are shown on Sheet 1 of the appended curves, from which it will be seen that the volumetric efficiency curves peak at 3150 R.P.M. with a value of 86.3% for the standard head, and at 3400 R.P.M. with 88% for No. Ramp head. Standard valve timing was used for each head, the inlet valve sizes being 1.400" diameter and 1.500" diameter respectively. MOTORING LOSSES. The power absorbed by friction, pumping, etc. has been estimated by measuring the power necessary to drive the engine at various speeds. This was conveniently accomplished by mounting a small car engine on trunnions and measuring its torque reaction when this engine was driving the single cylinder unit. Unfortunately, the unit had to be rotated in the reverse direction, but it is thought that this effect will not materially alter the results. The oil pump connections were, of course, reversed for this test. No attempt was made to analyse the losses. The figures will be found in terms of horse power and mean effective pressure on Sheet 2 of the curves. COMPARISON OF NO.2 RAMP AND STANDARD HEADS. Constructional Details : - No.2 Ramp. Standard. Compression ratio ......... 6.5 6.4 Inlet Valve dia. (normal) .... 1.500" 1.400" " " " (large) ...... 1.600" ----- Exhaust Valve Diameter ..... 1.400" 1.300" (Contd) | ||