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).
Spark plug suitability for high compression engines and issues with pre-ignition.
| Identifier | ExFiles\Box 19\7\ Scan136 | |
| Date | 18th April 1929 guessed | |
| contd :- -3- 2500 r.p.m. to give maximum power while the cast iron head needs approx. 43° advance. The fact that the non-turbulent head requires earlier timing of the spark and consequently has slower ignition of the compressed charge is in favour of it operating more or less normally under the influence of pre-igniting plugs. The quicker burning charge in the turbulent head would receive far too early ignition from an overheated plug - i.e. maximum pressure rise before top centre - and so the presence of pre-ignition would be more obvious than with the old type engine. Type of sparking plugs for high compression. We agree with E.{Mr Elliott - Chief Engineer} re. the suitability of sparking plugs for engines of different compression ratios and admit we do not consider the present standard plug (K.L.G. K1) used on the 20 HP. is at all suitable for high compression ratios. The construction of the plug is such that the mica insulation round the centre electrode, and which part is exposed to the flame, is simply wound round the electrode and not built up of compressed washers in the same way as the aero models. After pre-igniting for a few minutes this mica flakes away and becomes loose round the electrode and this is apparently the source of the pre-ignition. Mica wound round central electrode. Mica flakes off and unwinds after starting to pre-ignite. | ||