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).
Report comparing high and low compression engines, detailing issues with over-oiling, piston gas-tightness, and proposing modifications.
| Identifier | ExFiles\Box 77\3\ scan0192 | |
| Date | 10th September 1920 | |
| R.R. 285A (100 T) (S.H. 159. 11-8-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2800 -2- EP{G. Eric Platford - Chief Quality Engineer}2/F10.9.20. Contd. The HP all round, both high and low compression, is better, a better film of oil being maintained on the cylinder walls, in fact we now fear over-lubrication, as apart from more smoke from the exhaust, ignition plugs (intermediate) are oiling up, which is serious, and which we cannot pass. The present plugs will not stand much over-oiling, otherwise we prefer the over-oiling with its corresponding advantages. Mr. Hives has now an engine, investigating this weakness. We are now able to compete successfully with a really good pre-war car (60 lbs. compression by gauge), and even with a post-war low compression engine (55 lbs. by gauge) with same weight and gear ratio (same size tyres), acceleration at low engine speeds was quite as good, if anything slightly better. Hill climbing on top gear low speeds was the same and an advantage at high engine speeds. High compression engine (65 lbs. by gauge) - distinctly better on the latter point. These tests were also confirmed on the dynamometer, and although in a comparative test this is only one or two HP less at low speeds as shown on the dynamometer, the advantage of acceleration and hill combing at low engine speeds appears most marked. In previously bringing this matter up for discussion we have rather felt that the engines must improve with running, but we have had opportunities of testing post-war cars in the hands of owners (also pre-war owners) and which have run for some time (1600 miles - Sir Wm. Cain), who complain of poor power, and we must admit that the engine is disappointing as regards piston gas-tightness, and has the faults as explained above. Much as we may explain and demonstrate the advantage of higher engine speeds, he is a customer who never drives fast and always sticks on top gear until forced to change. It is such customers whom we have to accomodate, and we are proposing to fix pistons with extra rings, at any rate as a test case. We now await the convenience of the customer for us to attend to his car. We should like your comments and approval on this action. Contd. | ||