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 measuring sparking plug resistance under various engine running conditions and fuel mixtures.
| Identifier | ExFiles\Box 4\5\ 05-page189 | |
| Date | 5th May 1921 | |
| Contd. -3- Hsl/LG5.5.21. This condition was with very weak mixture picking up fullthrottle from low speeds. When the engine was running normally, we measured the resistance at the sparking plug points under different conditions. We did this by having an earth sparking plug fixed up on to each cylinder so that we could watch the sparking at the plug points. This plug was in parallel with the plug which was firing in the cylinder. The plug firing in the cylinder was set .020" gap. We adjusted the points on the external sparking plug until we just got an occasional jump. This test shewed us the following results :- Tests shewing the resistance at the plug points under different running conditions. Gap of external sparking plug in parallel with one firing in cylinder. Condition of running. Weak mixture. Normal mixture. Strong mixture. Dead-slow running. .065" .055" Full throttle - 500 revs. .100" .075" .060" 1000 " .100" .080" .060" 1500 " .080" .070" .050" 2000 " .070" .060" .050" When the engine is running full power continuously, there appears to be less resistance at the plug points, possibly due to the increased heat. It is sudden acceleration weak mixture which is the very worst condition. | ||