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).
Page 2 of a document describing the operation of a device to manage engine mixture, specifically the Smith Automatic Jet Control for an S.U. Carburetter.
| Identifier | ExFiles\Box 123\1\ scan0094 | |
| Date | 7th June 1938 guessed | |
| -2- So long as the engine is ticking over the mixture will remain partially rich, and will gradually move to the fully weak position as the engine warms up; thus it will be seen that whilst the engine is ticking over the device ensures that the mixture is not too rich. If the car is driven away the action of acceleration destroys the engine vacuum with the result that the mixture is again enriched and vice versa the mixture weakens when the accelerator is eased. This process of enriching the mixture during acceleration goes on until the engine has attained a temperature of 50 degrees centigrade, when the expansion of the Thermostat prevents any further movement and the Jet is maintained in the weak position. It will be noted that the degree of rich mixture for accelerating becomes less and less as the engine warms up and is in proportion to the temperature of the engine. The moving spindle connecting the bellows with the operating lever is made airtight by means of a rolling ring gland which being almost frictionless eliminates any possibility of variation in calibration. The device is extremely simple with very little to get out of order. Further it is absolutely foolproof, as in the unlikely event of Thermostat failure the vacuum in the induction manifold will overcome the resistance of the bellows and bring the Jet to the weak position. Also the liquid which would leak out under such conditions is drawn into the engine, or alternatively finds its way into the cooling water. There is, therefore, no danger resulting from thermostatic failure. Needless to say, the Smith Automatic Jet Control develops considerable power which is essential for operating the type of Jet used on the S.U. Carburetter. | ||