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).
Modifications to the Phantom III Stromberg carburettor and S.U. petrol pumps to resolve fuel starvation issues at high speeds.
| Identifier | ExFiles\Box 20\9\ Scan133 | |
| Date | 8th April 1936 | |
| X1033 To E.{Mr Elliott - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} c. to Mx.{John H Maddocks - Chief Proving Officer} c. to Ba. Ha/Swdl.{Len H. Swindell}19/KW.8.4.36. Phantom III Stromberg Carburettor & S.U. Petrol Pumps. Following the starvation trouble experienced at high speeds, the carburetter feed to the floatchamber was modified as follows. The existing horizontal feed blanked up and the union screwed in from the underside of the floatchamber, thus cutting out the right angle bend and making a direct passage through the union and the needle orifice. These pieces were produced by RHC{R. H. Coverley - Production Engineer}, and adapted to the carburetters on 32-EX & 33-EX, the conversion bringing the layout into line with the finalised scheme. Lec.4933 which calls for a new casting which is not yet available. The needle seat orifice is .179" dia. together with a special needle produced by the Zenith Co. to suit this diameter. Using the standard S.U. petrol pump, which has a free maximum flow of 240 pts/hr., the flow past the needle valve into the floatchamber is 180 pts/hr., the flow required to maintain the maximum power being 120 pts/hr. With this static flow of 180 pts/hr. into the floatchamber, Dodd has carried out tests at Brooklands without signs of starvation. From previous tests whereby with a static flow of 150 pts/hr., starvation took place. This indicates that this is not the true figure when the car is in action, and that there is some loss, possibly due to the bouncing of the float, thus cutting down the area past the needle orifice or the effect of the under-bonnet temperature or both. In conjunction with modifications to the carburetter, tests have been taken with the S.U. petrol pumps. The free flow as taken with a number of S.U. pumps is reasonably consistent and ranging from 225 pts/hr. to 250/pts/hr. | ||