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).
Analysis of engine performance concerning ignition timing, detonation, turbulence, and modifications to pistons and cylinder heads.
| Identifier | WestWitteringFiles\P\October1926-November1926\ Scan012 | |
| Date | 26th October 1926 guessed | |
| contd :- -2- ratio but considerably less intense than the 5.2 to 1 ratio used on car 10-EX. It was found that less ignition advance was required when the two ignitions were synchronised than when used singly. Very little difference existed between the advance required by either ignition when used alone but it seemed that slightly less advance was required by the plugs on the carburetter side of the engine. The intensity of detonation was unaffected by using either single ignition or the two ignitions synchronised, if in each case the advance was adjusted to give the maximum torque. The same power could be obtained with either the two synchronised or one used singly but as stated before more advance was necessary with one. The ignition advance required with a single ignition was however approximately the same as that with for the standard Phantom using both plugs simultaneously. It was expected that the arrangement of the head to promote turbulence would result in appreciably reducing the tendency to detonate and as the detonating propensities appeared but little removed from those of the std. engine it was thought perhaps the clearance between the cylinder head and the piston was a little too great to take the full advantage of this design. Furthermore, we still experienced continued firing after switching off the ignition, a trouble which previously we have thought to be connected in some way with the lack of turbulence. We consequently raised the pistons by means of packing under the pedestals until they came within .058 of the contd :- | ||