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 detonation, carbon deposits, and the desirable features for an induction pipe design.
| Identifier | ExFiles\Box 50\3\ Scan134 | |
| Date | 9th July 1921 guessed | |
| Sheet #4. The depositing of carbon appears from papers on the subject to be associated with liberation of hydrogen, and consequently with a tendency to detonate, as noticed in engines burning kerosene. This is far more marked with some brands of gasoline than with others, and we know of no way to overcome it, but believe that if the fuel is introduced in a finely divided state, it will tend to burn up more homogeneously, and with less detonation. We understand also that the attempt to extract a large percentage of gasoline from the crude, leads to an unstable gasoline which is more liable to detonate and deposit carbon. This perhaps may explain also why we obtained actual preignition on early tests with heated induction pipes. We would suggest that the desirable features of an induction pipe for this country were:- (a) Equal distribution when hot, by a heated throttle or other device which would reduce the gasoline on the walls, without seriously increasing the temperature of the inlet gas (above say 180° F.{Mr Friese}) because of loss of power and danger of detonation and preignition. (b) A pipe, as short as possible, so as to be able to reduce its sectional area, and thus obtain a maximum gas velocity for a given intake vacuum. This again with a view to overcoming wall condensation, or re-condensation of heavy ends beyond the hot spot. (c) A pipe with the minimum number of bends, to avoid wall condensation. (d) A pipe which slopes upwards all the way from carburetter to inlet valves to avoid the formation of pools of gasoline when running slow. All gasoline on the walls in slow running would then drain back towards the carburetter and not spot. (e) A pipe which heats up at the hot spot very quickly after a cold start. This is very important for avoiding crankcase dilution in winter. (f) A pipe which keeps hot all along beyond the hot spot even in the coldest weather without excessive engine house temperature, which could only be attained in winter by boiling the water. This could possibly be obtained by water jacketting or by conduction from the hot spot or from the exhaust manifolds, if cast in one piece with the inlet manifolds. (g) Heat regulation to the pipe for winter and summer, as suggested by Mr. Royce. We think that if the carburetter could be placed on the | ||