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).
Comparison of two ignition control schemes aimed at reducing fuel consumption and improving slow running.
| Identifier | ExFiles\Box 147\5\ scan0141 | |
| Date | 10th August 1937 | |
| c. Rm.{William Robotham - Chief Engineer} 1249? Da.{Bernard Day - Chassis Design}8/G.10.8.37. INCREASED IGNITION CONTROL. TO REDUCE FUEL CONSUMPTION. Rm.{William Robotham - Chief Engineer}13/R.28.7.37. The scheme referred to is a suggestion from E/Lid.{A. J. Lidsey} the object being to ensure that the ignition is fully retarded when the throttle is shut, primarily to obtain good slow running. The principal difference between this and the vacuum controlled advance is that an additional retard, say 5° to the TDC. can be obtained for slow running, on E/Lid{A. J. Lidsey}'s scheme, but not on the vacuum control scheme. This additional retard, however, functions adversely to petrol economy, when the throttle is shut at high speeds. The vacuum scheme retards only to the governor setting when the closing of the throttle cuts off the induction depression. Both schemes, however, give the advance of 10° to 15° at small throttle openings, so that the loss in economy may not be important. The cam introduced by Allwood in working out the scheme enables an additional advance to be obtained, like the vacuum scheme, but this advance depends on the geometrical position of the throttle and not on the engine speed, and so may cause detonation at low speeds. Since the vacuum scheme is simpler and almost certainly less costly than E/Lid{A. J. Lidsey}'s, we should be inclined to agree that we should not do any more work on the latter, as it seems to possess no outstanding advantage and some defects. DA.{Bernard Day - Chassis Design} | ||