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).
Summary of engine performance, vibration characteristics, and a comparison with a 20 HP model.
| Identifier | ExFiles\Box 5a\5\ 05-page016 | |
| Date | 30th March 1927 guessed | |
| contd :- -9- crankshaft in place of the fan pulley and proved effective in damping out this vibration to the extent that it was not evident by 'feel' or sound when on the test bed. This half speed vibration does not seem any more severe than experienced on the 20 HP. when it is run without the damper wheels. The engine accelerates well and there is no evidence of 'flat spots' due to the carbs. which are however set rather rich. SUMMARY & GENERAL CONCLUSIONS. --------------------------- The engine gives a very good performance for its size but, like most of the continental sports cars, is rather noisy in operation - chiefly valve gear and timing gear rattles. Some of the chief characteristics of the Lorraine compared with the 20 HP. are as follows :- (1) Maintains a good B.M.E.P. at high speeds. The B.M.E.P. increases with the speed up to its max: value at 2200 RPM. (2) High comp: ratio - 5.9 to 1 - and only detonates slightly at low speeds on ordinary low grade fuel. (3) Small amount of ignition advance required. Dual ignition requires appreciably less advance than single. (4) Low gas velocity past inlet valves which open and close rapidly and have long duration of opening. The inlet valve is still 73% of its max: lift when piston is at bottom centre. The 20 HP. inlet valve is only 53% open at bottom centre. The Lorraine exposes a considerable opening area after bottom centre. (5) The power to rotate the engine is greater than the 20 HP. after 2000 r.p.m. and increases rapidly. contd :- | ||