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).
The effectiveness of turbulent heads versus synchronised ignition in reducing spark advance and detonation on 20 HP and Phantom engines.
| Identifier | ExFiles\Box 54\5\ Scan301 | |
| Date | 7th March 1928 guessed | |
| contd :- -3- The Journal of the S.A.E. Aug. 1923. Naturally we should expect the turbulent type head to improve the 20 HP. with regard to detonations and ignition advance but we think the optimum results will be obtained by a combination of both the turbulent and synchronised ignition. Referring to the ignition curves for the Phantom we see that the dual synchronised ignition has done more to reduce the spark advance required than the turbulent head but we should imagine the synchronised ignition is more effective with the turbulent head than it would be on the present standard Phantom head. We had indication of this when experimenting with the experimental Phantom head, which was not of the turbulent type but had opposed sparking plugs like the Hispano, when it was found that the plugs on the carburetter side of the engine required more advance than those on the other side which we attributed due to lack of turbulence. It therefore followed that if the ignition were synchronised the plugs on the steering side of the engine took the lead. The effectiveness of the turbulent head in reducing spark advance seems more pronounced at the lower speeds - and this is where we want it in order to reduce the tendency to detonate - as can be seen from the curves given for single ignition on both turbulent and standard heads. Both heads require about the same advance at the higher speeds and this we think may be a feature of the 'two wave' turbulence, or double step head, resulting in interference or damping out of the turbulence at high engine speeds due to the two opposing waves. We have not been able to obtain contd:- | ||