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).
Engine performance tests, focusing on power output and cooling.
| Identifier | ExFiles\Box 133\2\ scan0150 | |
| Date | 14th June 1935 | |
| - 3 - Hs{Lord Ernest Hives - Chair}/Wd.{Mr Wood/Mr Whitehead}1/GB.14.6.35. POWER OUTPUT. It will be seen from the curves on sheet 2 (appended) that a maximum B.M.E.P. of 161.0 lbs/sq.in. is developed at 4500 R.P.M. under normal conditions. This is equivalent to 27.8 B.H.P. At 5500 R.P.M. the B.M.E.P. has fallen to 153.4 lbs/sq.in. and the B.H.P. risen to 32.5. The power is still rising at the maximum speed of 6000 R.P.M. with a value of 34.1 B.H.P. At speeds below the peak of the B.M.E.P. curve, the B.M.E.P. falls rather rapidly, thus at 3500 R.P.M. the B.M.E.P. is 143.0 lbs/sq.in. (19.2 B.H.P.) The power output of this engine depends to a large extent on the length of the exhaust pipes. The makers recommended exhaust pipes of 1300 c.c. capacity each. The importance of this point is illustrated by the dotted curves which were obtained simply by reducing the length of the pipes to approximately one-third the original dimension. It will be seen that the peak value of the B.M.E.P. is but 3.0 lbs/sq.in. lower, but at 6000 R.P.M. the difference is 20.0 lbs/sq.in. During the testing of this engine trouble was experienced with carburetter flooding (caused by vibration) and in order to prevent this the carburetter was mounted independently of the engine and connected thereto by a rubber connection. This alteration increased the length of the induction system by 2½" and the effect was to increase the power output up to 5600 R.P.M.; at higher speeds, however, the power fell below normal. The maximum gain is 8.0 lbs/sq.in. M.E.P. between 4000 and 4500 R.P.M. (See chain line curves, sheet 2). COOLING. During the tests to which reference is made in this report the unit was cooled by a Keith Blackman fan having a 11.5" diameter orifice capable of delivering an air blast of 90 M.P.H. For the majority of the tests the inlet to the fan was half throttled and the air-speed past the engine cylinder was approximately 50 M.P.H. | ||