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).
The principles and troubleshooting of the AC fuel pressure system.
Identifier | ExFiles\Box 27a\2\ Scan012 | |
Date | 12th August 1926 guessed | |
AC SPARK PLUG COMPANY #607 THE NEW AC FUEL PRESSURE SYSTEM CONTROL. PRESSURE CONTROL: Pump pressure is entirely a function of the spring used and the maximum pressure exerted on the carburetor occurs at a time when a minimum of fuel is used; namely, when motor is idling, hence when the pressure is correct with the motor idling, no trouble should be experienced at any other speeds. CAPACITY OF PUMP: The capacity of the pump in gallons per hour is a function of the maximum movement of the diaphragm and at high speeds of the weight of the spring used. A spring which will give a pressure of 2 lbs. to 2½ lbs. per square inch at idling will deliver 16 to 18 gallons at high speeds, which is 100% excess fuel for any motor on the market. COMMERCIAL CARBURETOR: Most carburetors will work satisfactorily with a 2 lb. pressure. STANDARD PUMP PRODUCT: A spring giving 1 lb. per square inch pressure is more than sufficient for 70% of the cars using a fuel feed system but from a manufacturing point of view it is very desirable to maintain a uniform product to cover the whole field and this would require a spring with a pressure slightly higher than 1 lb. per square inch. CAUSES OF PRESSURE TROUBLES: The trouble experienced with pressure to date are due to two causes: 1. Manufacturing errors 2. Installation errors 1. Manufacturing errors have been carefully analyzed and perfect control can be maintained: (a) By using a much longer spring which will give the same capacity in gallons per hours, but the spring itself will be less sensitive to variations of compressibility of 1/16" or less. (b) By weighing every spring with an allowable limit of plus or minus 3 oz. (c) By assembling the cover on the pump with the spring fully compressed, thus eliminating any possible stretch of the diaphragm. (The above conclusions are based on a number of tests which have given very uniform results considering the short sensitive spring used. See accompanying test record). | ||