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).
Performance test results comparing a standard Phantom III Stromberg Carburetter with a modified version featuring a reduced float ratio.
| Identifier | ExFiles\Box 122\2\ scan0142 | |
| Date | 18th March 1937 | |
| E.{Mr Elliott - Chief Engineer} from Rm{William Robotham - Chief Engineer}/GR.{George Ratcliffe} c. Hs.{Lord Ernest Hives - Chair} c. Da.{Bernard Day - Chassis Design} c. By.{R.W. Bailey - Chief Engineer} 1033 Rm{William Robotham - Chief Engineer}/GR{George Ratcliffe}7/R.18.3.37. P.III STROMBERG CARBURATTER - EEC.42. The present production carburetter is designed for a petrol feed of 3 lbs per square inch pressure. The S.U. pumps only give 3/4 lbs per square inch approximately. This means a reduction in fuel level of .350" at the maximum consumption of 112 PTS/Hr. By reducing the float ratio (LeC.5335) to suit the pressure of feed from the S.U. Pumps, we maintain a more constant fuel level in the floatchamber, i.e., a reduction of only .130" at 112 PTS/Hr. This now allows the fitting of smaller jets with improvement in consumption. The following tests were carried out at constant speeds on Brooklands Track. Mr. Maddocks, Test Dept. has also tested the modified carburetter and found it satisfactory. Standard Carburetter. Main Jets .058 By-pass jet .060 Max. speed 93 MPH.S.R. 1/2 mile 83.72 MPH. Lap. 83.0 MPH. Floatchamber to LeC.5335. Main jets .056 By-pass jet .050 Max. speed 94 MPH. SR. 1/2 mile 84.11 MPH. Lap. 83.7 MPH. MPH. NORMAL TOP GEAR. Diff: NORMAL TOP GEAR. Diff: OVERDRIVE. 30 6% Fast 14 MPG. 1.5 15.5 MPG. 2.3 17.8 MPG. 40 5.2% " 13.4 " .6 14.0 " 2.2 16.2 " 50 2.2% " 12.2 " .2 12.4 " 2.0 14.4 " 60 6.6% " 10.6 " Nil. 10.6 " 1.8 12.4 " 70 4.8% " 9.0 " .6 9.6 " 1.6 11.2 " 80 6.6% " 6.7 " .5 7.2 " 1.2 8.7 " 90 6.7% " 6.0 " .4 6.4 " 1.0 7.4 " Rm{William Robotham - Chief Engineer}/GR.{George Ratcliffe} | ||