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).
Tests of the 20/25 ignition system, finding the coil voltage insufficient and requesting a new design.
| Identifier | ExFiles\Box 54\5\ Scan339 | |
| Date | 4th December 1930 | |
| X5680. Ey. from EFC. EFC7/AD4.12.30. X.5680. 20/25 IGNITION SYSTEM X.5690 X.8712. As referred to in our EFC4/AD4.9.11.30 we have now carried out a test on each of two 20/25 NP chassis one experimental and one production, making use of a distributor head provided with windows. We found that although some amount of missing fire was experienced there was no corresponding sparking over to earth in the distributor head. This indicates, therefore, that the secondary voltage available from the coil itself is insufficient for these higher compression engines. We are also making tests, utilising a calibrated spark gap in parallel with the sparking plugs, to arrive at the actual sparking plug voltages in different circumstances, the results of which tests will be available later. Also, we are now asking for an ignition coil with a larger number of secondary turns (up to 21,000) to enable a higher voltage to be supplied. Previous records shew that we were aware of the small margin of voltage available even on the 20 HP. engine before the compression ratio was increased. EFC. | ||