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).
Letter discussing engine knocking, pre-ignition, fuel volatility, and performance of different gasoline types.
| Identifier | ExFiles\Box 75\2\ scan0238 | |
| Date | 2nd August 1921 guessed | |
| Oy2 - G 1821 Sheet #3. that it is generally recognized that the tendency to knock increases with decrease in volatility, and that it has been shown that the auto-ignition point in any series of hydrocarbons becomes lower as the boiling point rises. Therefore, I think you will realize that though with your fuel, lacking heavy ends as much as the gasoline of 1914 did in this country, you do not obtain knocking, with ours we may have very serious trouble with it, and may even get recognizable "pre-ignition". Platford will tell you how Gulf gas will knock in a new clean high compression engine, when other gasolines will hot, and I have written how on 102-CE, medium compression and dirty, on Gulf I could not get above 40 m.p.h., whereas on Socony the car was sweet and easy. The distillation curves may not show this tendency, as it depends on the nature of the heavy ends, since in one gas they may belong to a hydrocarbon series having less tendency to auto-ignite than in another. It was this knocking, pre-ignition, detonation - call it what you will - that put us off farther experimenting and made us settle down to our present form of pipe, as being the only safe thing we knew. We shall not feel safe in adopting any other sort of pipe, hot throttle, hot jacket, or whatever it may be, till we have tried one and definitely proved that with American gas, even Gulf or Sinclair, the worst we know for knocking, it will not reproduce the alarming symptoms of those early experiments. I may mention that the engine of Lockhart's car, on which we tested those pipes, was absolutely clean and had aluminum pistons. In the January, February and March Journals which I have sent you, there is scarcely an article which does not reek with facts and theories on fuel economy, fuel-knock, crankcase dilution, and other similar troubles which I have been writing you about. I want to recommend them all to your very earnest attention, because they represent our problems better than any letter of mine can do, and they all suggest cures. OY. M.{Mr Moon / Mr Moore} Olley | ||