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).
Investigating engine ignition timing, detonation, and spark plug positioning.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan291 | |
| Date | 12th August 1925 | |
| R.R. 493A (50 H) (D.D. 31, 12-8-25) J.H.D. EXPERIMENTAL REPORT. -3- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/ACL/A/M.S. 9.25. the engine gave signs of late ignition when the magneto was switched off and engine was running on right hand plugs only. By means of the spark position indicator, described later, it was discovered that the new plug position required more advance than the standard position consequently when both ignitions were synchronized with regard to time of sparking, the right hand plugs gave the effect of late ignition. From this we see that synchronized ignitions - or synchronized with regard to the time of sparking - with this plug position is little better, if any, than one ignition and to obtain the best results it would be necessary for the timing of each ignition to be related in such a way that the effective time of ignition coincided and not the time of sparking! In order to investigate more accurately the influence of the plug position and ignition timing on detonation and power we arranged the engine to operate on one cylinder only, having removed the pistons and connecting rods from the other five. The piston used gave a compression ratio of 5.2 to 1. A Goshawk carburetter replaced the standard. The angular position of the crankshaft when ignition took place was shown by means of an insulated pointer attached to the crankshaft which sparked on to an insulated disc marked in degrees and placed in the sparking plug circuit. A change over switch was provided so that either ignition could be used with the spark indicator. With this apparatus we were able to determine the amount of advance required by each ignition when used singly, or together. contd :- | ||