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).
Magneto ignition troubleshooting, focusing on spark plug gaps, voltage, and their effect on engine performance.
| Identifier | ExFiles\Box 4\5\ 05-page191 | |
| Date | 1st May 1921 | |
| Contd. -5- Hsl/LGS.5.21. ought to be able to appreciate it when we fit another magneto which gives a spark with a higher heat value with the same gap. As a further support to this, we all know that with the trembler ignition one has frequently switched on the ignition, the coil has buzzed, but a period of time has elapsed before the suggestion that the spark has to have a certain value in order to ignite the charge. We also found if we get the magneto plug points at .010", an engine is very difficult to start, if we alter nothing but open the points to .025" it will start easily. We feel convinced when there is a complaint of an engine running badly slowly on magneto ignition, it is not due to the spark not jumping at the points. Our tests have proved that the resistance at the spark plug points is comparatively slight under slow running conditions. The fact that we can open up the gaps to .100" without any definite misfiring shews that it cannot be that the spark does not jump at the points. We believe that in case where a Watford magneto is giving bad results slow running, it should be improved if the gaps were widened out more than our standard so as to increase the voltage at the sparking plug points. We cannot recommend this to be done because if we increase the gaps anything more than .020" we are certain to be in trouble with missing fire under full throttle weak mixture conditions. Under the full throttle condition we find that the difference which we have proved in the polarity of the spark has a very important bearing on our troubles. | ||