Engine performance issues related to weak fuel mixtures, high exhaust valve temperatures and valve stretching.
| Identifier | ExFiles\Box 11\3\ 03-page446 | |
| Date | 23th July 1931 | |
| 87941 G.W. Hancock Esq., Hotel de France, Chatearoux, Indre, FRANCE. From Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} 4/MJ.23.7.31. We believe it is frequently the practice to run with very weak mixtures in order to get a good consumption. It occurs to us that the figures on the Daily Reports show such good consumption for the average speeds maintained, that the car may part of the time have been running too weak. As you know, one of the easiest ways to raise the exhaust valve temperature is to run with a weak mixture, in fact with our racing engine we can preignite any time we like by weakening off. We think that in view of these facts you should make a special study of mixture strength in connection with this exhaust valve stretching. We have been going carefully into the shape of the exhaust valve for cooling round the seat, material, etc., and apart from the long toe on the cam which keeps the valve just off its seat for a considerable period, we cannot see any reason why we should run into this trouble. The generally accepted theory is that raising the compression ratio makes the exhaust valves run cooler, and so we cannot attribute the trouble to this feature. We await your report with interest. Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} | ||
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).