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).
Test report on plug voltage at various plug gaps and water temperatures for different engine cylinders.
| Identifier | ExFiles\Box 54\5\ Scan344 | |
| Date | 17th December 1930 | |
| -3- EFC1/AD17.12.30 contd. (b) Plug gaps .025" Water temperature 95 to 100°C. Cylinder No. Plug voltage 1 5300 3 6020 6 4700 (c) Plug gaps .030" Water temperature 70°C. Cylinder No. Plug voltage 1 4700 2 4820 3 6600 4 6020 5 5920 6 7650 Average maximum voltage per plug 5950. (d) Plug gaps .030" Water temperature 95 to 100°C. Cylinder No. Plug voltage 1 3900 3 5300 6 5400 These results shew that the plug voltage with .025" and .030" gaps is about the same. We can only explain this by the fact that the gap setting was very critical and that the plugs in the .030" case may have been hotter. With the plugs very hot there is a voltage reduction of about 15%. 20/25 HP. Chassis. (a) Plug gaps .020" Water temperature 70°C. Cylinder No. Plug voltage 1 5920 2 6020 3 7200 4 6600 5 6300 6 5920 Average maximum voltage per plug 6330. | ||