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).
Resolving excessive fuel consumption by modifying the carburetter's stand pipe and float chamber.
Identifier | ExFiles\Box 13\4\ 04-page100 | |
Date | 6th February 1933 | |
-2- Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}5/MA.6.2.33. Cont'd.{John DeLooze - Company Secretary} Satisfactory diametrical clearance between the piston and its chamber was found to be (.004). Metering. In original form the consumption at high speeds was excessive and found to be almost unaffected by jet size or condition of the diffuser. This only occurred when the intake body was bolted up to the carburetter intake and resulted in increasing the consumption from 30 to 120 pints/hour at 3000 R.P.M. By blanking the passage which supplies the stand pipe above the taper needle fit, the trouble was overcome underall conditions. Investigation of the depression of these points with the passage blanked shewed that under the condition of excessive consumption, the depression in the stand pipe is 2.3 Ins.H2O whilst the float chamber depression is nil at 3000 R.P.M. The height of the stand pipe above the petrol level is 1.5 Ins., thus any difference in excess of this figure results in sucking petrol over the stand pipe into the engine. In order to effect a cure, it was necessary to either :- (a) Decrease the depression in the stand pipe or, (b) Raise the height of the stand pipe or, (c) Increase the floatchamber depression. (a) Extensions on the open ended base of the piston guide spindle and protruding into the intake did not affect the existing depression in the stand pipe. Various tests with tubes and washers of different forms were tried without improvement. (b) By raising the stand pipe .75" which is as high as the existing design allows, the trouble was improved and only occasionally occurred. (c) By fitting an extension pipe, pepper potted at the end into the floatchamber vent hole and protruding in the intake, the floatchamber depression was increased from nil to 2.0 INS.H2O whilst the stand pipe depression remained at 2.9 INS.H2O. This completely overcame the | ||