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 testing regarding ignition timing, air intake shielding, and fuel recommendations for different throttle levels.
| Identifier | ExFiles\Box 36\2\ scan 189 | |
| Date | 10th October 1928 guessed | |
| contd :- -5- virtually later time of ignition from the plug in the exhaust gas region. It would therefore seem we could with advantage arrange the controls to give still more lead to the exhaust mag. relative to the inlet when adjusted for throttled positions. To determine the best relative timing it would be, of course, necessary for this to be the subject of an experiment. We ran this test with the ignition control separated from the throttle control in order to increase the advance as the engine was throttled. It was found when running at the last throttled stage - 120 HP. - the max. economy position came very near the unstable region. The air intakes were consequently shielded from the draught of the test bed cooling fan and enabled us to run well free from the 'popping' point. At these low powers the air intakes velocity is very low and it is conceivable that a high velocity air stream over the intakes could result in internal disturbance and so interfere with the balance. This indicates the importance of careful attention to the air intakes when the engine is installed in the machine and rather suggests the trial of gauze intakes under the engine cowling or the forward reduced air intakes. We did not find any advantage in employing high air intake temperatures but it is quite possible inferior results would attend very low air temps. such as encountered at high altitudes. For the full throttle running we recommend 100% Benzol as this gives entire absence of detonation, freedom from plug trouble and good power and economy. contd:- | ||