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).
Analysis of ignition coil weakness and misfiring related to ballast resistance and spark timing.
| Identifier | WestWitteringFiles\I\October1922\ Scan60 | |
| Date | 28th October 1922 | |
| EFCL/T28.10.22. -3- Contd. as would be expected, in the most unfavourable condition for the ignition, viz. hot condition of engine, and ballast resistance, acceleration or slow running under load with retarded spark. With these improved coils, the phenomenon is not produceable with the spark advanced, but is more or less easily produceable with the spark more retarded than central, according to the amount of retard. Owing to the good results attained by these coils on the bench tests, results which satisfy our specification, it began to be considered that it must be some other feature of the ignition than the coil. At every possibility other than the coil having been considered, and experiments made upon it, such as different bakelite rotors, different H.T. distributor heads, different condensers, different voltages of supply and different amounts of ballast resistance within reason, the whole matter has brought us back again to the conclusion that the weakness lies in the coil. It would be expected that if a weakness existed with the original standard length of ballast resistance (32"), (we have since made this 25" and may yet possibly reduce it to 20") and that short circuiting the ballast resistance eliminated the misfiring, there would be some shorter length of ballast which would be entirely satisfactory, but we have found this not to be the case without reducing the ballast and short circuit resistance to an amount which makes the running currents | ||