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).
Engine ignition advance, combustion chamber shape, and second ignition plug positioning.
| Identifier | ExFiles\Box 72\4\ scan0172 | |
| Date | 10th April 1924 | |
| To E.{Mr Elliott - Chief Engineer} HS.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. to CJ. RG.{Mr Rowledge} DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} S E C R E T. X9770 E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C. ENGINE. X.9780. X.9770. The question is why do we need more advance? Probably the shape of combustion chamber, but one might imagine that there was considerable difference in compression pressure (not necessarily ratio) supposing Hispano filling up or better ramming at high speeds. E.{Mr Elliott - Chief Engineer} is looking out for a better position of 2nd. ignition plug. He also has our scheme for advancing both automatically which seems to require 25° which I read are crank degrees, plus about 30° [REDACTED] initial, so as to be 10° safe for starting and retarded 5° more than enough at 500 so as to reduce detonations at slow speed. The figures would change if another position for second plug is found. MADE AT CROXLEY R.{Sir Henry Royce} | ||