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).
Summary of engine tests on the lighter Phantom engine, comparing valve sizes and ignition advance.
| Identifier | WestWitteringFiles\Q\December1926-January1927\ 43 | |
| Date | 1st December 1926 guessed | |
| contd :- -6- The spark advance required proved to be on the average slightly less than for the standard valves on the same head but more than necessary for the head provided with the larger deflecting ledges. Curves are given on sheets 1 and 2 comparing the ignition advance for each engine or head. With regard to detonation and self ignition we could detect no difference due to the smaller valves. Comparing the power output with large and small valves we find a definite loss resulting from the use of the smaller (see curves on sheet 3.) This amounts to 5.9% at 2500 r.p.m. Considering the results obtained with the smaller valves we find no benefit to be derived from their use. SUMMARY. The following is a summary of the results of our tests on the lighter Phantom engine :- (1) The head LeC.2230 which has the smaller opening into the combustion space requires less spark advance than any of the others tested and considerably less than the standard Phantom engine. (2) Best results are obtained with the ignition synchronised over the whole speed range and results in an appreciable reduction of the advance necessary compared with single ignition. (3) The tendency to self ignite after switching off the ignition is much less evident than with the std. Phantom and is expected to result in an improvement in practice. contd :- | ||