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).
Engine slow running issues related to spark plug gaps and magneto performance.
| Identifier | ExFiles\Box 4\5\ 05-page190 | |
| Date | 5th May 1921 | |
| Contd. -4- Hsl/LG5.5.21. With the engine running normally we found, on the road, that we get good slow running if we opened the spark gaps of the plugs to .125". There was no definite misfiring slow running. If we tried to open up, of course, the engine stopped. After the tests we have made and our experience on the cars as regards magneto complaints, our conclusions are as follows :- The most frequent complaint we get quoted against the E6. Watford magneto compared with the pre-War Bosch, is that the slow running of the engine is not as consistently good. We believe this is due to the fact that the heat value of the spark from the Watford magneto is not as high as that from the Bosch. To support this argument, we quote the following facts. We all know the marked difference that can be obtained in the slow running of an engine by adjusting the width of the spark plug gap. It is possible to appreciate in the slow running of an engine the difference between a plug gap set at .020" and .025", or perhaps within narrower limits than that. When we analyse the effect of opening up the plug points, we can only see that effect is to increase the voltage at the sparking plug points and to increase the heat value of the spark. If that is so, then it is reasonable to imagine that if we can appreciate the difference in the heat value of the spark by opening the gaps a few thousandths, we | ||