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).
Equation for engine carburation control and its application to cold starting and acceleration.
| Identifier | ExFiles\Box 41\4\ Scan026 | |
| Date | 29th January 1930 guessed | |
| - 3 - This depends on the assumption - P1 + KP2 = Constant. Where P1 is the pressure at T.D.C., which may in practice be either sample taken for ignition, since these are balanced. P2= Intake vacuum in lbs/sq.in. below atmospheric. K = A constant for any type of engine, found by dynamometer test, and based on the engine operating under all sorts of loads and speeds but under best conditions of mixture, spark advance, temperature. etc. K apparently varies between about 7 and 10 for different engine types. Mr. Stanton states that within his experience on dynamometer-test of engines such a relation always exists, and though not exact is near enough to produce a greatly improved functioning of the engine when applied to carburation, etc. By balancing the pressure and the required multiple of the intake vacuum against a soft spring (simulating a weight) and using this combination to control the mixture etc. the best functioning of the engine can be automatically controlled for all conditions of cold starting, sudden acceleration etc. The mechanism can even control a common carburetter choke valve and take this operation for cold starting entirely out of the driver's hands. (This was done on Mr. Stanton's demonstration car). The only difficulty is which way to control the mixture, since regulation either weak or rich will decrease power. Consideration of starting makes it necessary to provide that when there is no vacuum the mixture should be full rich, so that increase of vacuum or increase of working pressure is made to weaken the mixture. Thus the mixture is held rich on a cold engine through lack of working pressure, and is made rich on acceleration through sudden decrease in vacuum. It is necessary to adopt some safeguards as follows:- 1. The carburetter may be set slightly weak so that when warm the engine will not drop pressure through overrichness. If this occurred the control would go on increasing the richness. - continued - | ||