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).
Report discussing engine detonation, ignition advance, and spark plug positioning.
| Identifier | ExFiles\Box 134\2\ scan0164 | |
| Date | 16th October 1937 | |
| -2- (3) Detonation. Detonation was stated to be influenced to a great extent by the gas velocity through the throat, and if this were too high trouble would be encountered. This confirms our own results, which indicate that too small a throat area has extremely detrimental effects on detonation. The type of gasket most suited to the engine was discussed and C and A appear to be the best. If, however, the copper does not adhere closely to the asbestos packing on the edges, fraying of the copper appears to take place, giving rise to sharp edges and poor detonation qualities. Detonation was also increased if two C and A packings were fitted, even though the compression ratio were reduced thereby. A method of getting over this difficulty was to fit one C and A washer and one metal one, when things appeared OK. An explanation of this phenomenon is probably that the two centre layers of copper become extremely hot, due to lack of metal to conduct the heat away, giving rise to similar conditions to those cited above. Cylinder head material, it was stated, appeared to have very little effect, and cast iron or alum could be used with only very slight variations in the detonation characteristics. (4) Ignition Advance. It was thought by Coventry Climax that the ignition advance obtained on the inclined valve head was rather large, and that we might find a curve similar to that obtained with the de-turbulated No.2 head rather better, due to its being rather flatter. We are, however, inclined to doubt this, and in any case other considerations make No. 4 head superior to No. 2. (5) Plug Position and Reach. The plug points should be as near as possible to the inlet valve, in the interests of good starting and slow running, so that the incoming charge sweeps over them. Verifying our own results, it was stated that as the plug points move away from the inlet valve towards the exhaust valve, so does ignition advance increase, Cont'd | ||