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).
Thermal efficiency, carburettor settings, and ignition advance, including a graph of brake load vs spark lead.
| Identifier | ExFiles\Box 147\5\ scan0094 | |
| Date | 12th June 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-6-25) J.H.D. EXPERIMENTAL REPORT. -10- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}/LG21.11.25. thermal efficiency dropping from 17% to 11% with no appreciable loss in power. As for accelerating and starting from cold, an over-rich mixture is required, there is a ~~tendency~~ to set the carburetter too strong, the power will still be O.K. when the engine is warm, but the optimum petrol power consumption will not be obtained. Therefore whenever a carb. setting has been altered it is as well to suspect it of having been set over strong. For freak petrol cons., power will be sacrificed. It should be noted, however, how disasterous are the results of setting the carburetter over-weak. GRAPH V.{VIENNA} (Graph showing Brake Load (Lbs.) vs.{J. Vickers} Lead of Spark (Degrees)) Labels on graph: PINKING, KNOCKING. IGNITION ADVANCE. If the best possible consumption at partial engine loads is to be obtained, more ignition advance than std. should be used. Std. ignition advance is dictated by the tendency of the engine to knock under full load. As will be seen from graph V.{VIENNA} at very small contd :- | ||