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).
Experiments with carburetter throat size and diffuser jets to increase power in the 20 HP engine.
| Identifier | ExFiles\Box 5\4\ 04-page156 | |
| Date | 11th January 1926 guessed | |
| contd :- -6- The metal thickness between the cylinder bores and the induction passage with the large diameter is .075" and makes casting more difficult. CARBURETTER THROAT SIZE. By increasing the throat size we get only a very small increase in power - 2½% increase of power for 57% increase of effective throat area. Increasing the high speed throat results in impairing the metering of the carburetter at low depressions. DIFFUSER JET FOR HIGH SPEED THROAT. This jet gives no appreciable improvement in power although slightly better efficiency is obtainable in with weak mixtures. This however is outside the range xxx within which we work in xxx practice. Generally, we see that all the above experiments which have been carried out with the modified parts give us no solution to an increase of power. We are however starting to work on a careful investigation in the endeavour to determine the source, or sources, of power loss in the 20 HP. engine. All the above results apply to the standard 4.78 compression ratio engine and it is possible, when the source of loss is discovered and removed, then such alterations as have been tried in the above tests - i.e. larger throttle and throats - may result in increased power. Hs{Lord Ernest Hives - Chair}/A.C.Lovesey. | ||