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 tests on pre-ignition, overheating, and detonation, noting the effect of charge temperature.
| Identifier | ExFiles\Box 34\2\ Scan104 | |
| Date | 15th May 1918 | |
| Contd. -3- arranged two plugs which fired from separate magnetos. One magneto was set standard and was running the engine; the other was set to pre-ignite. We could, by means of high tension switches run on either plug so that we could see the heat build up when pre-igniting and watch it cool down again when we switched on to the standard plug. From these further tests we wish to qualify our previous statement that we could not produce over-heating by pre-igniting a spark. If proper conditions are obtained over-heating can be caused by the spark. During all these tests we have noticed that a most important factor is the temperature of the charge at the time of the ignition. The first thing we noticed when we ran with oil in the jackets at 150 to 175°C was that the engine detonated, not very badly but quite distinctly. This is only what one would expect because keeping the combustion chamber hot by means of high temperature oil in the water jackets has the same effect as carbon deposit in the combustion chamber. The effect is to warm up the charge so that it fires more rapidly. It fires so rapidly that it detonates. One knows, detonations are always worse at lowspeed, full power, it gradually disappears as the speed increases. We attribute this to the fact that at low speeds there is more time for the charge to be warmed up. It is not a question of compression because we know that remains fairly constant over fairly wide range. Another point which frequently occurs on the car CONTD | ||