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).
Investigation into engine misfiring on Bentley engines using leaded (Ethyl) petrol.
| Identifier | ExFiles\Box 162\4\ img167 | |
| Date | 7th September 1936 | |
| Ea/Sut.S/E.L./7.9.36. MISFIRING OF ENGINES RUNNING WITH ETHYL PETROL. Several cases of misfiring on Bentley engines have been recorded where these engines have been run using leaded fuel. The trouble has been most elusive as it has not been easily possible to produce it at will on any particular car. No trouble was reported prior to the use of leaded fuel and where a car has been used and driven hard with ethyl there has been no complaint. The missing occurs after the engine has been run light or on light loads for a considerable time, such as using the car in dense traffic, and then attempting to open up at high speed. In each of the cases investigated missing commenced at about 3000 engine R.P.M. although when cool there was also misfiring on the "pick-up". The "pick-up" misfire we believe we have cured by reversing the coil polarity but we wish to try this further before finally deciding on its virtue. The high speed misfire was traced to the sparking plugs, which when cleaned cured the missing It was concluded therefore that the deposits on the insulator of the plug consequent upon the use of the lead in the fuel were the cause of the trouble. We have often heard of these deposits causing missing on cars but have never actually identified the trouble with the use of lead on our cars until now. 10,000 miles tests in France, or test running in Derby have not shewn up this trouble. The deposits on the insulators when analysed were mostly lead oxide and Carbon whereas on the inside shell of the plug, lead Bromide predominated. This analysis is usual on sparking plugs used with Ethyl with the exception that there should be no carbon present. This suggests that the plugs were running too cool. Two plugs were then subjected to an electrical leakage | ||