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).
Continued notes on engine performance modifications, test conclusions, and plans for further development on a 20 HP engine and the Phantom.
| Identifier | ExFiles\Box 5a\5\ 05-page053 | |
| Date | 31th March 1927 guessed | |
| contd :- -5- (2) The speed of max. output was raised from 2650 r.p.m. to above 3000 r.p.m. (3) The B.M.E.P. was increased from 120 lbs/sq.in. to 124.3 lbs/sq.in. and the speed of max. B.M.E.P. was raised from 1750 r.p.m. to 2500 r.p.m. (4) To obtain the above advantage it was necessary to employ carburetters giving a low induction manifold depression. (5) A total gain of 30.5 HP. has been effected by :- (a) Raising the compression to 5.45 to 1. (b) Employing 1.400 dia. valves giving 60% greater area than std. when fully lifted. (c) Using two Zenith carbs. which lowered the induction pipe depress: from 3.5 in. to .5 ins.Hg. (d) Using inlet and exhaust cams giving respectively 23° and 12° longer duration relative to the crankshaft. CONCLUSIONS : We have demonstrated by the above tests that we can make the 20 HP. KA. engine equal and better the performance of such engines as the Lorraine Dietrich. The B.M.E.P. curve given by the 20 HP. we consider superior to the Lorraine. Before we can take full advantage of these factors to increase the output it will be necessary to modify the crankshaft in order to avoid the main resonant speed which at present exists at 3200 r.p.m. This job is in hand in which the present crankshaft is being modified to take the 1-G-1 type of damper for the purpose of experiment. FURTHER DEVELOPMENT : It is proposed to prepare a similar camshaft for the Phantom. It is also proposed to carry out similar experiments on F.10. camshaft in order to obtain the max. B.M.E.P. at the normal | ||