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).
Optimal position of a sparking plug in an engine cylinder.
| Identifier | ExFiles\Box 33\5\ Scan100 | |
| Date | 18th July 1916 | |
| EH To E.H. from R.{Sir Henry Royce} c. to J.{Mr Johnson W.M.} COPY. XQ025 R9/W18716. July 18th, 1916. RE SPARKING PLUG POSITION - X.2025. With reference to your memo of June 27th, re sparking plug position, we shall be glad to know if you consider the position in the side of cylinder is more likely to get oiled up than is the standard position on the top. We always considered that it would be much more dangerous from this point of view. We should also like to know whether you can detect any definite difference in the tendency to detonate as we found that from the little engine at LeCanadel and from the Bugatti a decided tendency to detonate even with overhead valves when the ignition plug is brought to one side of the combustion chamber as in the side position mentioned above and that used in the Mercedes racer. * We notice that you say there is a difference of about 7° in the advance necessary to get the full power even at 1350 revs. This would undoubtedly get worse as the speed went higher and would constitute a decided disadvantage in an engine for a car where there is great speed variation, viz., want of the need to adjust ignition more often or the result would be less satisfactory. * The disadvantage of this is generally overcome by double ignition with plugs at opposite sides of the combustion chamber. R.{Sir Henry Royce} | ||