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).
Pre-ignition limits and subsequent gas leakage tests on various spark plugs.
| Identifier | ExFiles\Box 58\2\ Scan076 | |
| Date | 3rd May 1934 guessed | |
| 4. E&I.827. Table 4. Pre-ignition limits (Method "B"). | Plug. | Highest B.M.E.P. for no pre-ignition. lb/sq.inch. | Plug washer temperature. | Rear of cyl: head temp: | |----------|---------------------------------------------------|--------------------------|-------------------------| | A.G.10 | 120 | 288°C. | 203°C. | | A.G.20 | 123 | 288°C. | 203°C. | | A.G.30 | 129 | 276°C. | 206°C. | | Standard | 134 | 290°C. | 210°C. | The fuel, compression ratio, mixture strength, air temperature and R.P.M. were such that detonation did not occur during any of the tests. Plug washer temperatures were taken on the same side of the engine in each case. The B.M.E.P's have been corrected for bed losses and are comparable with those of a multi-cylinder engine. The results show that the Siemens plugs have a lower pre-ignition limit than standard aero plugs. 6. Gas leakage tests subsequent to engine tests. Subsequent to the pre-ignition tests in the Mercury V single cylinder unit each of the plugs was again tested for gas leakage at 100 lb.per sq.inch and atmospheric temperature. The results are compared with those obtained previous to the pre-ignition tests and are given in table 5 below:- Table 5. Gas leakage results before and after pre-ignition tests. | Plug. | Leak before engine tests. | Leak after engine tests. | Remarks. | |---------|---------------------------|--------------------------|------------------------------------------------------| | A.G.10. | | | | | 1. | 0.8 cu.cm/min. | 1.09 cu.cm/min. | Leak from top of insulator. | | 2. | 0.3 " " | 1.5 " " | ditto. | | A.G.20. | | | | | 1. | 3.3 cu.cm/min. | 2.5 cu.cm/min. | Leak from top of insulator. | | 2. | 5.6 " " | 12.0 " " | ditto. | | A.G.30. | | | | | 1. | 1.0 cu.cm/min. | 5.52 cu.cm/min. | Leak from top of insulator & slight from gland. | | 2. | Nil. | 2.74 " " | Leak from top of insulator. | | ||